The Grapevine Asfaw ZellekeThe Asfaw Grapevine 2013

Asfaw Zelleke The Abay Renaissance Dam: An Eternal Source of Hydro Power Supply and Irrigation Sor Prosperity, Sovereignty and Integrity of the Motherland

Cover Photo: Black Corinth, a raisin variety at DZARC 00O2>(

Ethiopian Institute of Agricultural Research Central The Grapevine LIBRARY f h.+V'Kf f ’J’flC? 9°C9°C VNH'K- ft,'h

Asfaw Zelleke © Copyright 2013, Asfaw Zelleke

All rights reserved. No reproduction, copy or transmission of this book may be made without the author's written permission

Copyediting and Design: Abebe Kirub Elizabeth Baslyos Girma Kassa EIAR

First published 2013

Published by: EIAR Printed by: e t h - c a n a p l c . Addis Ababa

ISBN 978- 99944-53-74-x To my deai' sister the late Emahoye Tiruwork Zelleke and to those who aspire to embark on initiation, production and promotion of the fruit of antiquity. Contents

F o r e w o r d ...... i Pream ble...... ii Preface...... iii- Introduction...... 1 Chapter 1 ...... 3 The Grapevines...... 3 Description...... 3 Categories of Grapes...... 4 Climatic Requirement...... 6 Global Economic Importance...... 8 Production of Grapes in Ethiopia...... 10 Chapter I I ...... 11 Structure am! Growth Processes of the Grapevines...... 11 Morphology...... 11 Growth Processes of the Grapevines...... 19 Phenology...... 22 Physiology and chemistry of berry development...... 26 Chapter III ...... 29 Propagation...... 29 Production of Own Rooted Cuttings...... 32 Production of Rooted Cuttings of Rootstock...... 34 Field Propagation...... 36 Rapid Propagation Techniques...... 43 Chapter IV ...... 49 Establishing Vineyards...... 49 Site Selection...... 49 Pre-Planting Activities...... 51 Planting and Time of Planting...... 53 Chapter V ...... 56 Husbandry of Grapevines...... 56 Managing Vineyards...... 56 Managing young vines...... 58 Pruning...... 59 Types of Training/Pruning...... 62 Canopy Microclimate and Canopy Management...... 64 Diseases and Insect Pest Control...... 68 Post - harvest Vineyard Management...... 68 Chapter V I ...... 69 Mineral Nutrition of Grapevine...... 69 The Macronutrients...... 72 The micronutrients...... 81 Laboratory Diagnostic Methods...... 88 Chapter V II ...... 92 Problems of Production...... 92 Biotic Stress...... 93 Bactcrial Diseases...... 98 V iru s...... 99 Insect Pests...... 100 Vertebrates...... 105 B ird s...... 107 Disorders...... , ...... 108 Chapter VIII...... 110 Categories o f Grapes...... 110 Wine Grapes...... 110 Table Grapes...... 115 Raisin Grapes...... 124 Grapes for Other Purposes...... 132 Chapter I X ...... 135 Varieties...... 135 Fruiting...... 135 Wine Grape Varities...... 135 Table Grape Varieties...... 141 Raisin Grape Varieties...... 143 Rootstocks...... 144 References...... 148 Glossary...... 162 In d e x ...... 173 Endorsements...... 183-84 Illustration

The files not acknowledged in legends are from the author’s file collected during his post-graduate study at the University of California, Davis.

* The parts and functions of the grapevine 12 The compound (1,2 & 3) buds and the fourth (4) bud 13 The flowers of grapevine: complete flower (a), pistilate flower (b) and staminate flower (c) 15 Parts of the grape cluster 16 Cluster shapes of grapes 17 Main shapes of the vinifera berries 18 Grape berry growth and development 25 Cutting (a), rooted cutting (b) and rooted cutting prepared for field planting (c) 30 Pruning shear 30 Grafting Knife 37 Steps in whip or tongue grafting 38 Cleft grafting (A) and notch grafting (B) 40 Steps in chip budding 41 Budding Knife 41 • Steps in T- budding 42 Simple layering: replacing missing vine using canes of adjacent vine 43 Head-trained, spur-pruned vine 62 Ilead-trained, canc-pruned vine 63 Horizontal bilateral cordon-trained, spur-pruned vine 63 Overhead arbor-trained vines 64 List of tables

Some popular varieties of vinifera grapes 6 Days to maturity, degree-days and °Brix of some wine grape varieties grown under Debre Zeit condition 8 The world’s ten top grape producing countries and their production status 10 Berry size and other parameters categories 18 Media composition for grapevine shoots tip culture 45 Murashige and Skoog Revised Media Composition of Basal Medium 46 Number of vines per hectare at different vine and row spacing 53 Grapevine growth and yield indices* for optimal wine grape canopy management 68 The levels of mineral nutrients under different conditions in leaf tissue sample 71 Nitrogen application guidelines for mature and young vines 74 Commonly available commercial sources of nitrogen and the amount needed to supply the respective nitrogen rates per hectare 76 Estimated nutrient requirement of grapes under tropical conditions 88 Nutrient content of different organic fertilizers 88 Different levels of macro-and-micro nutrient elements in vine tissue of some grapevine varieties 91 The influence of grape maturity (°Brix) on drying ratio, sugar and acid contents and weight of 100 Thompson Seedless berries (15% moisture) 132 Mineral, vitamin and other food composition of Thompson Seedless raisins 132 Foreword

The grape and wine industries in Ethiopia have long desired a practical book on general viticulture such as this book as the need to provide guide has become increasingly pressing in recent years. The book is the first one on viticulture in foreign language by a native Emerinis-Viticulturist who rendered long time services since late 1963 at various posts as instructor, researcher and advisor to graduate students in research centers and universities, and as administrator at higher echelon of civil service until his noble exit in 2008 due to retirement. It is unequivocal that this book will make a major contribution to modernizing the grape industry by translating theory into practice pertaining to the principle of grape growing in Ethiopia as well as other developing countries where grape production is one of their priorities. With profound awareness for the need of such books in the research and teaching endeavors of research and higher earning institutions, and in the area of grapevine production and development as priority in the transformation scheme of the nation, I very sincerely hope hat other retirees would follow suit. It is also my strong conviction that every dedicated viticulturist, wine producer, instructor, investor and others concerned with grapevine, will be keenly interested in this book. Its publication is particularly opportune because of the recent changes and/or emphases on research strategy given to viticulture by the government and hence researches centers and academic institutions, and the unduly emerging interested investors on this untouched but potentially viable subsector. Hence, I feel that research centers, higher learning institutions, development organizations and many individuals who henceforth cannot afford to be without a copy of this book.

Fentahune Mengistu Director General, Ethiopian Institute of Agricultural Research

[i] Pream ble

Production of scientific publication has been a major constraint in many of the research and development institutions. It is gratifying indeed that producing research results has become a routine exercise as those of the slogan of publish or perish. Publish or perish has nearly become instituted in the research and higher learning institutions. Thus, publishing research results have become a .veil established culture within these institutions.

The time and energy required to prepare books as a reference material or for teaching is unequivocal and should be encouraged. The book entitled “The grapevine” to my knowledge is the first of its kind prepared in a foreign language in the country. The book is so simple to understand. It contains all the important aspects of viticulture and is very informative. It will have high value in areas of teaching, extension and development works.

TSie author whom I have known for a long time both as a student at Jimma Agricultural and Technical School and the then Alcmaya University of Agriculture and later on as a colleague at Debrc Zcit Agricultural Research Center has great charisma with extremely high zealous attitude in all the responsibilities bestowed upon him. Of course, as a well-trained viticulturist, this is the least expected of him. Nonetheless, he certainly deserves recognition as distinguished citizcn and meritorious scholar.

The information that this book provides as a guide towards improving production and productivity of grapes in toio is a remarkable contribution by the author. It is worth mentioning that today the demand for Ethiopian wines in the foreign markets show a s.'cady increase beyond and above the attainable capacity of the winery primarily because of shortage of raw materials (fresh grapes).. Hence, it is clear that the grapevine can play an important role in generating foreign currency through exporting quality wines. On the other hand, though precisc statistical data are not available, the country is importing huge quantities of raisins primarily for making sacramental juice ia Churches, for the production of wines for domestic market and in pastry for making cookies and cakes by spending exuberantly huge sum of foreign currency. This clearly indicates that the chance of self-sufficiency in the case of grape production is possible and bright. What is needed is intensification of its production. Therefore, I am an optimist visionary that with the support of the Government in recognizing the crop and providing the necessary inputs: and with this book as a guide there is a bright future for the country to establish and promote the grape industry and become a successful competitor in the global markets.

Taye Bezuneh Senior Horticulturist and Private Consultant

[ii] Preface

This book is prepared as a refcrcncc material in support of the scaling up grapevine technologies in the research and extension programs of research and development institutions and as a course in viticulture at the higher learning institutions. The main features of the book are its simplicity of its exposition and its extensive use of figures illustrating the main practical aspect of viticulture. The book is organized in nine chapters and a glossary with definitions of important terminologies. A clear description of the grapevine that includes categories, climatic requirement, economic importance and production of grapes in Ethiopia is made at the outset in Chapter I. The structure (morphology) and growth processes (phenology), physiology and chemistry of the grapevines are presented in Chapter II. The subject of propagation is treated in Chapter III Establishment of vineyards is covered in Chapter IV. Husbandry of grapevines is dealt in Chapter V. A general nutrient requirement of the vine is presented in Chapter VI. Chapter VII is devoted exclusively to production problems. Categories of grapes and important varieties are the subject matter of Chapters VIII and IX. respectively.

I feel that it would be unfair to pass without mentioning in the preface, the main oojectivc and the driving forcc or thrust for the initiation in the preparation of this book. The idea of preparing a simple handbook was initiated in the early 1970s, while I uas a post-graduate student at the University of California. Davis (USA). At that time, the sources of information in the area of viticulture was limited to only the 2nd edition of “General Viticulture” authored by Winkler et al. in 1974 coupled with exclusive interactions with prominent scientists in the Department of Viticulture and Enology at the University. Despite the fact that certain aspects of viticulture were available in the form of printouts, leaflets, etc. there were no consolidated sources of information available other than the book mentioned. Eventually, the experience acquired during the teaching and research assignment at Ambo Junior College of Agriculture also became a springboard towards strengthening the decision to preparing an introductory manual or handbook on the subject. Therefore, this book is prepared as a source of general information for teaching general viticulture and as a guide and reference for extension agents, growers and researchers. It was started in the middle of the 1980s and took such a long time to bring it to its final stage. The long gap was not without reasons. I was engaged in teaching and research, and oddly enough in routine administration assignments for most of the years, since my return to my beloved country after the completion of the post-graduate program. Finally, in the aftermath of my retirement in late 2008, conditions became too favorable to complete the book and thus justifying that time constraints was the real causc for the delay.

I wish to express to all those who made the preparation of this book possible. From the outset, I am particularly indebted to H.E. the late Ato Abcbe Rcta, the then Minister of Agriculture, for stimulating my interest in viticulture while I was serving as a lecturer at Ambo Junior College of Agriculture in the 1960s and for the subsequent scholarship award I was granted to pursue a specialization training in viticulture at the University

[iii] of California, Davis. Hence, without giving to order of particular importance, I would like to express my heartfelt appreciation to the following individuals.

I am grateful to Professor Ravishnkra* for his constructive criticisms and suggestions on the contents of the book during his tenure as a member of the Faculty of Agriculture, at the then Alemaya University of Agriculture, now Haramaya University. The comments and suggestions offered by Professor Daulta* and Professor Pal* at same University and Dr. Taye Bizxmeh (Private Consultant) are appreciated. Particular acknowledgement is due to Ato Abebe Kirub, Professor Ravishankar and Dr. Derbew Belew for their skilled editorial assistance.

I also wish to acknowledge all my colleagues who have made helpful suggestions and criticisms for various portion of the manuscript. The invaluable assistance of Ato Biniyam Yalemtesfa in the preparation of the table of contents, illustrations, tables and Jie index is very much appreciated. The assistance rendered by Dr. Kebede W/Tsadik )f Haramaya University in the preparation of some parts of the initial draft is highly appreciated. Thanks are particularly offered to Awash Wine Share Company for the modest financial assistance offered during the preparation of the first draft. My special vhanks and gratitude go to Ato Kidanemariatn Hagos and Ato Kassahun Biru for their invaluable assistance in preparing the figures presented in the book.

I am deeply indebted to the Managements of Ethiopian Institute of Agricultural Research for the great encouragement, the honor bestowed on me and publishing the book; and the Debre Zeit Research Centre for the provision of office space with full facilities at the Centre that facilitated the completion of the book successfully without further delay. I humbly admit that it would have not been possible without it. The support of dear friends and colleagues, Dr Kassahun Aberu and Ato Mesfin Tshomc, is indeed an incentive and absolutely positive encouragement to work harder similarly in the future.

Finally, I am grateful to my wife, Turuworq Engida, and to my children, Nathan, Yafet and Meron for their patience and good spirit during the writing of this book. They have truly shared since its mid-gestation, which was much longer than expectcd. My wife, Tiruworq also deserves appreciation for the long unflagging secretarial assistance.

Asfaw Zelleke September 201}

[iv] Introduction

The grapevine (Vitis vinifera L.) is one of the table delicacies of the world. It occupies nuch larger area as compared to other subtropical fruits worldwide. Its association with human beings is older than wheat, rice, tef, sorghum etc. Grapevine cultivation is known from 7000 B.C. Evidences, to this cffcct, are documented in Egypt sincc 3000 3.C. The primary ccnter of origin of the crop is the Transcaucasian region of the main canter of the ccntral Asiatic origin. Its culture began in the Asia Minor, the region between the Black and the Caspian Seas. From here, it spread westwards to Greece, Italy and Germany and eastwards to Persia and India. The year and route of introduction of grapevines to the African Continent however, has not properly documented. The common belief is that grape is introduced to North Africa first, from the Mediterranean areas from where it spread to the other African countries including Ethiopia. The introduction of grapevines to Ethiopia is not well documented, although the use of raisins dates back to the fourth century with the introduction of Christianity. Juice made from grapes/raisins is used as “sacred" in the Ethiopian Orthodox Church.

The fruits are good source of calcium, phosphorus, iron and vitamins (B1 and B2). It is also a good source of carbohydrates (15-25 %) of which, dextrose (glucose) and ievulose (fructose) constitute about 8-13 and 7-12 %, respectively. It also contains 0.2- 1.0 % tartaric acid and 0.1-0.8 % malic acid. The juice is a mild laxative and acts as stimulant to kidneys. Over 80% of the global grapes production is for wine, 9% for [able and 6% for raisin. Therefore, in countries where the grapevine is extensively cultivated, it has significant economic importance as a potential source of national revenue.

The Italians, during their occupation in 1935-42, arc believed to have introduced grapevine into the country. Since then, few individuals both foreigners and the natives evinccd interest to grow grapevines in small areas mainly to sell fresh fruits to consumers and to a smaller extent to the local wineries.

Until the 1974 revolution, growing grapes was not considered important. The attention given by research ccntcrs in particular and the government in general was insignificant. After the revolution, some of the vineyards have been abandoned /destroyed. The government maintained only a small vineyard at Kilinto 10 km from Ambo Town and 3 hectares at Guder in the premises of Ambo University of Agriculture loeated at about 15 km west of Ambo town. The destruction of these vineyards could be attributed at least in part, to their small sizes (few hectares) that were scattered in different locations, which could not be placed as part of the state owned vineyards.

In the mid 1970s, the Government had established vineyard on 40 hectares in Zewai at about 165 km southeast of Addis Ababa on the way to Awassa. At the same time, healthy and clean planting materials of some promising varieties were introduced from California and Europe. The Debre Zeit Agricultural Research Center had planted these varieties in Debre Zeit and Merti Jcju on replicated plot as observation trial. However, because of lack of adequate information on the adaptability of these varieties under

[1] Asfaw Zelleke

Ethiopian condition, the performance of these varieties remained unsatisfactory for a long time. Consequendy, the wineries continued importing raisins for making wines for the domestic market. The tremendous potential for expanding tropical viticulture in the country with appropriate technology has been recognized and effort is being exerted for improving production and productivity. The improvement of productivity especially using suitable varieties, proper training systems, integrated nutrient management, pests and disease management would unequivocally facilitate the establishment of sound commercial viticulture industry.

[2] The Grapevine Chapter I

The Grapevines

Description

he grapevine belongs to the family Vitaceae genus Vitis. Vitaceae has members that ^ are mostly woody or herbaceous trees, climbing plants or shrubs. The family is inter- tropical in its distribution. They are characterized by the presence of tendrils and nflorescence opposite to leaves. The genus Vitis contains over 60 species found mainly in the temperate zones of the Northern hemisphere. Vitis vinifera L is the most important and widely cultivated species. It has two sub-genera, the Euvitis and Muscadinia.

Euvitis is the true grape, which has longitudinally striate-fibrous bark, nodes with diaphragm, forked tendrils, elongated flower cluster, berries adhering to the stem at maturity, pyriform seeds with beak.

Muscadinia has a bark that has no lenticels. Nodes are without diaphragm and tendrils are simple. The Euvitis sub-genus has two distinct spccies known as Vitis vinifera and the American species.

Vitis vinifera-. The species is native to Caspian and Black Seas areas and referred to as the Old World grape, the European grape and more recently as Californian grape (Winkler et al., 1974). It is known as fruit bearing species and thus produces over 90% of the world's grapes. The grapes grown in Europe and other regions are either pure vinifera or its hybrids. There are thirteen pure species that include: vinifera, labnisca, aestivalis, riparia, rotundfolia, lincecumii, champini, longii, doanima, mpestris, candicans, monticola, and berlandieri.

The hybrids are produced by crossing a variety of one species with a variety of another species or with existing hybrids. It can also be obtained by crossing tw'o hybrids varieties with each other. The majority of the hybrid crosscs are made between labrusca and vinifera species.

The American species'. These are the American native species most of which are used as rootstock. The problem of soil pests such as phylloxera and nematodes that devastated the grapevine in the United States of America had been solved by using the American specics or their hybrids as rootstock.

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Morphological description of the different commercial cultivars and rootstocks used to control soil pests and other problems arc presented in Chapter IX.

Cultivar Classification The main cultivars of grapevines are classified based on their morphological similarities and geographical distribution. The dev elopment of ampclography, the art and science of grapevine description and classification made significant contributions [o the identification of the grapevines cultivars. In ampelography, cultivars are identified based on two main morphological characteristics, i.e.. the shape of the leaf ind pubescence of the shoot-tip (Allweldet and Detvvciler, 1992). Thus, the description if each cultivar comprises a drawing of the outline of a typical fully expanded leaf and a brief statement containing quantitative and qualitative information like ratio of length of the lateral veins to the length of the main vein, the sum of the angles formed by certain veins.

Categories of Grapes The commercial grapes are categorized by use into four major groups. These are: wine grapes, table grapes, raisin grapes, juice grapes or canning grapes. These are briefly discussed below. All grape varieties can ferment into wine when crushed albeit only a few of them will produce wine of high standard quality. Most of the varieties can be eaten fresh or dried as raisin while few others varieties are grown primarily as table grapes or fresh fruit. Nonetheless, the production of wine, table and raisin grapes in the world is based on traditional cultivars of litis vinifera. These have been perpetuated mainly through vegetativ e propagation. Some of these cultivars are widely grown in many grape-growing countries while the rest arc of strictly temperate zone importance. The names of few popular wine, table and raisin grapes cultivars arc listed in Table 1.

Wine grapes: Few cultivars of wine grapes have achieved great international prominence. These include Cabernet Sauv ignon, Chardonnay and Pinot noir (French origin) and Riesling (German origin). In Ethiopia, an appreciable amount of raisins and concentrated must are imported for wine making. Wines made from imported materials are inferior in quality. They arc mainly produced for the local market. Wines made from locally produced fresh grapes represent a small portion of the total wine market. The quality of wine made from fresh grapes is good, but amount of grapes produced is not enough to satisfy the demand of the wineries. Increasing grape production will enable quality wine production for domestic and export markets leading to sustainable self-sufficiency in quality wine production.

7able Grapes: Grapes eaten as fresh fruit are table grapes. In Ethiopia, grapes have been cultivated mainly to supply raw materials to the local wineries albeit some amount is retailed indiscriminately as fresh grapes. Consumers also use the same grapes as table grape with no specific preference or choice of varieties. This could be attributed to lack of awareness of the different classes of grape cultivars that are suited

[4] The Grapevine for different uses. It is therefore difficult to project the demand for table grapes for ocal consumption. Currently, research strategies are focusing on evaluating cultivars for tabic use at different agro-ccologies in order to facilitate its production for local and export markets. The desirable characteristics to be adapted in standardizing table grapes are size, color, taste and seedlcssncss of berries. The consumers usually prefer arge sized berries with attractive color and good taste.

Raisin Grapes: All cultivars arc not suitable for raisin production. Seedless grapes with high total soluble solids are preferred. The color, flavor and texture following dehydration are additional quality factors. The most important factors include:

• brittleness • medium-sized berries, • uniformity in brilliance of color. • good condition of berry surface, • good texture of the skin and pulp. • moisture content of < 15%, • good flavor (sweetness) • absence of decay (rot), mold and yeast, of extraneous matter, and • free from insect infestation or contamination by insect remains and excreta.

Juice Grapes: Juices are produced using the natural fresh grapes from those varieties that give sweet and acccptablc beverages when preserved by pasteurization and filtration retaining its flavor throughout the proccss of clarification and preservation. It is important to note that pasteurization affects the natural flavor of grapes. Most Vitis vinifera varieties lose their fresh flavor and develop an unpleasant “cooked” flavor when pasteurized.

Canning Grapes: Seedless varieties are canned in combination with other fruits in fruit salads or cocktails.

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Table 1. Some popular cultivars of vinifera grapes

For Red Wine For White Wine For Table and Raisin Grapes Name Ongin Name Origin Name Origin Aramon S. France (Fr) Chardonnay Burgundy, Almeria (T) Spain France. Cabernet Chenin blanc Loire valley, Black Corinth (R) Greece France Bordeaux France. Cabernet Colombard Chaenet. Cardinal Fresno, Sauvignon Boreaux France. (T) California. Carignane S. France Traminor Germany Emperor (T) Ancient M/East Gamay Beaujolais, Riesling Germany Flame Tokay (T) Ancient France. Spain Grenache Rhone Valley, Sauvignon Loire Valley, Italia (T) Italy Rose France. blanc France. Merlot Bordeaux Semilion Bordeaux, Muscat of Ancient France. Alexandria (R) M/East Mataro Spain Sylvaner Germany, Muscat Hamburg France Austria (T) Nebbiolo N. Italy Ugni blanc Italy Perlette (T) Davis. Calif. Pinot Noir Burgundy, Fr. Ribier (T) Belgium Syrah (Shiraz) Rhone Valley, Thompson Ancient France. Seedless M/East Sultana (TR) Ruby Davis, Cabernet California. Carnelion Davis, Calif. Source: Winkler et al. 1974; T = Table grape; R = Raisin grape; TR = Table & Raisin grape: Fr= France

Climatic Requirement A complex of factors determines the commercial success of a viticulture industry with climate being the dominant one. Grapevines arc endemic to the warm temperate zones between 34° and 49° North and South latitudes. The most northerly distribution of vineyards is in Germany in the Rhine Valley, where it is grown between 50° and 51° North latitude (Winkler et al., 1974). For successful production of grapes, the mean annual temperature is the most critical factor. A given temperature would be suitable for grape production if the mean temperature of the warmest month exceeds 19°C and that of the eoldest month is above 0UC (Prescott, 1965). Commercial viticulture though is concentrated in the temperate zone limited acrcage under grapes outside these general areas including tropical ones could be seen. Usually, under this situation, it requires specialized horticultural practices such as inducing bud rest through withholding water and defoliation, or the cultivation of grapevines at high altitudes where temperatures are relatively cool. Likewise, in the tropics, at higher altitude vines adapt easily as under temperate zone conditions Otherwise, they arc almost evergreen, produce relatively fair and tend to be short in their productive life.

The vinifera species requires long warm to hot. dry growing season and cool dormant period. Humid growing period or rain early in the growing season is conducive for the proliferation of microorganisms and poses difficulty in controlling them. Rains or

[6] The Grapevine cloudy weather during the blooming period affects berry set. Under warm climatc. the grapes tend to lose dclicacy and richness, which affects the aroma of grapes.

In general, temperature is considered as the predominant climatic factor affecting growth and development of the grapevines (Butrosse, 1968). Rainfall, humidity and daylight could also affect grapevine growth but to a limited extent than the effect of heat summation. Heat summation is the sum of the mean monthly temperatures above 10°C from bloom to maturity (respectively, October - February at Debre Zeit) under any grape growing condition. The base line is set at 10°C for there is almost no shoot growth below this (Winkler el al. 1974). It is expressed as dcgrec-days. For example, in Dcbrc Zeit in the month of November if the mean temperature is 15°C, the summation is 5-dcgree days (15 - 10) per day and 150 degree days (5 X 30) for the month. If the mean temperature for the month of November is 14°C, the summation is 120 degree-days. The effect of heat summation under tropical condition needs to be studied in relation to the degree Brix (°Brix) or percent sugar of the fruit. The data in Table 2 indicate number of days to reach maturity, heat summation and °Brix of some grapevine cultivars grown at Debre Zeit. Awash Winery tested these cultivars for wine quality for three consecutive years (1996 - 1998). Most of these cultivars were found suitable for the production of good quality wines.

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Table 2. Days to maturity, degree-days and °Brix of some wine rape cultivars grown under Debre Zeit condition o CD =]. Cultivar Days to maturity Degree days X Black Hamburg* 185 1142.35 19.0 Blauer Traulinger 190 1184.40 18.6 Cheniin blanc* 169 1177.75 25.5 Cannonano 190 1297.35 24.8 Dodoma Aleatico 205 1406.90 21.8 Dolcetto 178 1142.35 22.2 Grenache blanche* 184 1297.15 23.2 Grenache noir* 195 1323.70 24.2 Petrit Syrah 164 1198.35 23.8 Sangiovese (Tikur)* 172 1315.10 20.2 Tannat noir 184 1087.05 20.8 Ugni blanc* 150 1157.85 25.0 Source: Debre Zeit Research Center (2000/01) * released and registered in the National Released variety Register in 2004

The vinifera grape is a highly adaptable species and can be grown in a wide range of environment. Wine grapes grown in deserts (California), table grapes in mountains (Indonesia) and at sea level (Thailand) are cultivated successfully. The limitation lowevcr could be countered by inputs of husbandry or technology like irrigation ('California), labor for plant manipulation (Indonesia and Thailand).

Global Economic Importance Today grape cultivation has become one of the most remuneration farming enterprise in many countries of die world. Production has become alarmingly changing constantly from year to years. This apparently made it difficult to give precisc information on acreage (or ha) and yield (t) of production and volume (L) of wine produced globally in certain years. Very few leading countries that are engaged in the sector are mentioned and a table is provided to show their comparative position. The FAO Corporate Document Repository (2007) gave brief account on grape production status in Asia-Pacific. The report mentioned that famous Indian scholars have written in 1356 - 1200 BC about the medicinal properties of grapes. India has the distinction of achieving the highest productivity and minimizing risk in grapes in the world with an average of 30 tons per hectare. Sustaining productivity and minimizing risk has become possible because of the availability of new technologies coupled with agro- climatic regions that are suitable for cultivation and production of tabic and raisin grapes. Furthermore, double cropping and harvesting twice or more in a year in certain regions and availability of suitable varieties and technologies to producc quality grapes for the respective uses contributed immensely for higher demand of the crop. Conventional technologies by cross hybridization, though with certain limitations, have contributed to the development of the grape industry (Prof. Olmo, Univ. Calif. Davis, personal communication).

In the USA and Europe and other countries in Africa (South Africa) and Oceania (Australia) extensive research and innovation, endeavors arc underway to effect constant transformation in grape growing. In the USA grape production has

[8] The Grapevine consistently constituted one of the largest non-citrus fruit crops, often competing with apples for the greatest amount of total fruit production (Winkler et a l 1974). The situation report and statistics for the world viticulture sector (01V, 2004) indicated that in the USA the farm value of grape has totaled approximately USD 1.5 to 2 billion each year since 1980s even though commercial grape production is limited to only three States (California, Oregon and New York). California alone produces about 90% of the country’s grapes. The California Table Grape Commission has identified several important trends that benefit the grape industry. First, health-conscious consumers find that grapes meet all the criteria in nutrition; secondly the large number of high-income households has increased the demand for convenience food items, and thirdly, school children play a growing role with grapes as their number one snack food choice. California also hosts a thriving vineyard economy, producing many world famous red and white wines. The red wine cultivars include Zinfandcl, Cabernet Sauvignon and Merlot that constituted about 59% with about 40% of the white wines made from Chardonnav, French Colombard and Chcnin blanc.

In Europe, Spain, Italy, Francc and Germany produce huge quantities of grapes on considerably large size of land areas mainly for the production of wines as indicated in the table below.

'he position of grape production in the African Continent is also changing. The North African countries such as Algeria, Tunisia and Morocco have been producing wine- grapc since the “era of colonization”. Today, the crop is economically well recognized and many countries in the Eastern and Southern part of the Continent are producing grapes primarily for wine production. South Africa ranks top while Egypt has become potential producer of fresh grapes. In Tanzania, Kenya and Uganda grape production has gained momentum to become a remunerative farming enterprise (Schultz and Dc’try, 1990). In Ethiopia, the interest manifested by the State coupled with interested investors for the establishment of vineyards has become alarmingly increasing. The establishment of new vineyards for fresh grapes production for the export markets does continue to increase, but slowly (Olmo, 1984). Current position of grapes production though insignificant, in terms of acreage and total output, production per hectare in Ethiopia (-180 qs) is highly competitive with some pioneer countries in grape production such as France (~90 qs), Italy (-100 qs), Australia (-117 qs) and South Africa (-150 qs). This trend, more likely, will improve with better cultural practices management) and suitable varieties.

The top six countries in grape production in 2007, in chronological order were, Spain, France, Italy, Turkey, China and USA with Australia ranking 10th and 7th in grape and wine production, respectively and 4th in wine exporting (Table 3).

[9] Asfaw Zelleke

Table 3. The world's ten top grape producing countries and their production status

Production Acreage Total Grape Wine Fresh grapes Raisin Export Country (,000 ha) Mil.qs) (Mil. HL) (Mill, qs) grapes (Mil. qs) (Mil.qs) Spain 1,169 60 34.70 NMG NMG 15.3 France 867 65 48.40 NMG NMG 15.2 Italy 800 73 48.00 127.0 NMG 18.8 Turkey 525 34 NMG 15.5 3.688 NMG China 500 62 12.00 37 755 NMG USA 409 58 20.00 8.6 3,300 4.2 Iran 338 30 NMG 18.3 2,102 NMG Argentina 231 31 15.00 NMG 202 3.6 Chile 197 25 8.20 8.1 660 6.1 Australia 174 15 9.60 NMG 150 7.8 World 5,663 526 227.80 142.1 12,196 83.7 Source: OIV. 2008. Report on the state of viticulture world market. 6th General assembly of OIV (www.oiv int/oiv/into/enconjoncture) NMG = not major goal of production in these countries qs = quintals (100 kg)

Production o£ Grapes in Ethiopia In Ethiopia the importance of grape cultivation was realized in the mid 1970s. State- owned vineyards were established in the Rift Valley. Planting materials were introduced from California and Germany. Since early 1980s and with the establishment of Horticultural Development Corporation in the late 1970s, commcrcial cultivation of grapes had gained momentum up until the downfall of the Derge Regime. Grape cultivation is largely confined to Zewai, Nura Era and Merti Jcju areas with altitudes ranging from 1100 to 1600 meter and annual rainfall of 326-1200 mm. The quality of grapes is satisfactory with total soluble solids reaching 20 to 22% (°Brix) comparable to any good grape growing areas of the world. The bouquet, flavor and sugar: acid ratio of slow ripening grapes in Gudcr (2008 masl), a highland area, are better quality; while at lower altitudes in Zewai, Nura Era and Merti Jeju grapes have higher sugar content, but less bouquet and body. Such areas are suitable to produce raisin and fresh/ table grapes. In spite of the unlimited potential to expand the production of grapes, absence of sound guidelines for streamlining the arts and science of grape production, establishing sound commercial grape production deserves special attention. It is therefore, the author's strong conviction that this book even though it covcrs general viticulture could provide valuable information for the establishment of new vineyards and maintaining the existing ones towards commercially sustainable production of grapes in the country.

[10] The Grapevine Chapter II

Structure and Growth Processes of the Grapevines

Morphology

I Jke any other plants, the grapevine also consists of well developed underground part, the root, and above ground part, the trunk, arm and shoot (Figure 1).

The Roots: Underground part In the grapevines, the development of the root system starts on propagating materials. Usually cuttings are adopted as planting materials. Roots arise from meristematic regions adventitiously near the surface of the cutting. Most roots develop at nodal positions near a bud. At the start of each growing season, the dormant roots develop new absorbing roots from the meristematic regions (Pratt, 1974) and subsequently producc new branch roots, rootlets, or feeder roots. These rootlets increase the absorption surface of the roots and become very important. The roots have three distinct parts, namely the cap located at the tip of the root; the zone of elongation, and (he zone of absorption of water and mineral nutrients from the soils. The absorption zone is characterized by having many elongated epidermal cells forming root hairs that ncrease the absorbing area. The development of root hairs is governed by soil pH. In alkaline soils, only few root hairs are likely to develop. The roots are the main suppliers of water and mineral nutrients to the whole plant system. Therefore, the rate of penetration in the soil profile appears to be of significant importance in optimizing .he water-nutrient requirement of the vines. The roots of the grapevines penetrate deeply and spread laterally in the soil where most of them are located in the upper 1.5 m and penetrate deep often to 3 m or more. Root penetration may be limited to the upper surface of the soil profile because of hardpans, shallow soil and water tables. The main function of the root system is absorption, anchorage and storage.

[11] Asfaw Zelleke

Parts Function

Tendril Support

Cluster Photosynthesis Transpiration Respiration Node

Leaf Fruit production

Main branch of the Arm trunk, supports fruiting units (spur &canes)

Trunk ------Support Conduction

Soil line ------>-

Anchorage Roots ------Absorption Food storage Feeder roots

Figure 1. The parts and functions of the grapevine

The Shoots: Above Ground Parts The above ground parts of the grapev ines consist of the trunk, anns and shoots on which leaves, buds, tendrils, flowers and fruits are borne (Figure I).

The trunk: It is the main stem of the vine functioning as the connecting link between the underground (root) and aboveground (shoot ) parts of the vine. Water and minerals absorbed by the roots are transferred to the leaves through the trunk. It is in these leaves food is manufactured for nourishment of the whole vine. Similarly, portion of the food materials is also transferred through the phloem - food-conducting tissue of the trunk, to the root. The trunk provides support to the canopy of leaves and other parts.

[12] The Grapevine

The arm: It is the main branch of the trunk older than one year (in cordon trained vines). The spur and the canes, which are maintained at pruning time for production of crops, arc located on the arm/trunk.

The shoot: It is the succulent stem with leaves arising from a bud. The current season’s top growth bears the flower and fruit. Lateral shoot arises from the primary shoot soon after the primary shoot begins active growth. The lateral shoots produce leaves and sometime dusters.

The cane: It is a matured one-year-old shoot that provides cuttings for propagation purposes.

The tendril: It is a lateral leafless branch, which has its own specialized origin, structure and function (Pratt, 1974). The tendril acts as a support by attaching to an object (wire, support). The vinifera species has discontinuous tendrils where two of the adjacent leaves have tendrils and the third leaf without a tendril.

The bud: It is a dormant or undeveloped shoot. A bud develops from meristem axillary to a leaf Buds are classified according to their stages of development as lateral, the primary, and two secondary buds. The two secondary buds are considered as secondary and tertiary buds in most literatures (Figure 2). The primary and the two secondary buds arc grouped together, and appear as one bud and hence referred to as an “eye” or a compound bud or simply as bud. The primary bud usually gives rise to the primary shoot that develops on spur or canc. As long as the primary bud is functional and develop well, the other two buds remain dormant. It is at times when the primary bud is killed or damaged that one of the secondary buds will develop and grow to replace the dead bud. Moreover, the result of an investigation on bud fruitfulness at the nstitute of Grapevine Breeding at Geibclrhoef (Germany) revealed the presence of a fourth bud. which was identified for the first time (Zelleke and During, 1994).

LS = Leaf scar; Lat. = lateral

Figure 2. The compound (1, 2 & 3) buds and the fourth (4) bud

[13] Asfaw Zelleke

The prcscnce of such buds in the grapevine puts it to a unique position, as this kind of bud development is not common in any other fruit trees. During the process of bud development, some undeveloped bud remains embedded in old trunk or arm. These buds arc called latent buds, which usually give rise to weak growing shoots, called water sprouts. In the grapevines in general tv\o types of buds are required based on development of leaves or flowers. These are leaf bud and flower bud. A leaf bud produces shoots with rudimentary leaves and flower duster. A fruit bud develop into shoot that can bear 1 to 3 clusters located opposite the leaves on the lower and/or ccntral portion of the shoot. In the temperate /one, the eluster primordia arc developed in the dormant buds prcccding the year in which flowering and fruiting occur. This however requires further study under tropical and subtropical conditions.

The leaf: The general structure of grapevine leaves is similar to leaves of other fruit trees. Perhaps the only difference among grapevine cultivars may be the size, shape, hairless, and/or presence of hair (pubescent). Moreover, in the grapevines most of the stomata arc located on the lower epidermis and may be few to none on the upper epidermis.

The leaf blades arc indented and most have five lobes. The shape of the leaves, the sinuses between lobes, the shape and nature of petiole sinus, presence and absence of tooth on leaf margins are major tools used in grapevine ampelography varietals identification or description.

The flower: The flower primordia of the grapcx ines arc initiated in the preceding year in which flowering and fruiting occur. Most vinifera varieties have perfect (hermaphrodite) flowers (Figure 3a) where, both the stamens and the pistil are functional. Pistlatc or female (Figure 3b) flowers have undeveloped pistil - a stigma and style arc missing but contains a small ovary, which cannot be fertilized. Staminate or male (Figure 3c) flowers have short and refluxcd stamens and produce sterile pollen. Many spccics of the grapes arc dioecious. Male flowers arc borne on one-plant and female flowers (functionally pistilatc) on another. Such varieties require inter-planting of male flower with female flower producing vines. For practical purposes, however only verities having higher percentage of hermaphrodite flowers should be selected for cultivation. Flowers arc borne in clusters and several hundred flowers may be found per cluster.

Pollination and fertilization: The transfer of pollen grain from the stamen to the stigma is referred to as pollination. Under favorable conditions, the pollen grain germinates. In the grapevines, anthcsis occurs between 6:00 and 9:00 in the morning and 2:00 and 4:00 in the afternoon (Pratt, 1971). Pollen tube penetrates the stigma and grows down in the style to the ovary (the embryo sac) where fertilization takes place. According to Pratt, fertilization occurs 2 or 3 days after pollination. After pollination, the ovary develops into berry.

[14] The Grapevine

Figure 3. The flowers of grapevine: complete flower (a), pistilate flower (b) and staminate flower (c)

Hie Cluster: The grape cluster consists of peduncle, rachis, cap stem (pcdiclcs) and berries (Figure 4). The rachis is the main axis of the cluster and the individual flowers are borne on a pedicle. The peduncle is the portion of the cluster from the shoot to the Irst branch of the cluster. The grape cluster is the most valuable part of the vine. Apart from its food value, it has naturally interested ampclographers. They have allocated a great deal importance to the grape cluster and have used it for as the basis for their classification even though differences that occur between grape clusters are not consistent. It is clear that in the grapevines a number of factors such as type of soil, amount of fertilization, rainfall and irrigation, training system, severity of pruning, placement of fruit bud on the cane, condition of the time of bloom and fruit set and chemical treatment (growth regulators) affects cluster/fruit production). It is, therefore, difficult to designate one specific type of fruit cluster for each variety and impossible to establish a system of classification based on cluster.

[15] Asfaw Zelleke

Peduncle

Lateral Pedicel Rachis

Figure 4. Parts of the grape cluster

Cluster Weight: The size, shape as well as size and number of the berries determine weight of clusters. According to Winkler et al. (1974), the cluster weight is categorized into six weight (g) classcs as follows: very small (<50); small (50 - 125), medium small (126 - 250), medium large (251 - 500), large (501 - 1000) and very large (> 1000).

Cluster size: Grape clusters are categorized in five classes based on length of cluster, which varies from 3 to 50 cm (Winkler et a\. 1974). These are described as follows: very small (<6), small (6 - 12), medium (12 - 18), large (18 - 24) and very large (>24).

Cluster Shape: The shape of the cluster/bunch varies considerably among varieties. There are various types of clusters such as cylindrical, conical or pyramidal, globular or round. The shape of clusters depends on the number and length of the lateral branch of the cluster stem. Thus, in cylindrical eluster (Figure 5) the main axis of the cluster has only primary lateral branches of equal length. If the lateral branch bccomcs small towards the tip. the cluster will be "conical". Shouldered eluster have well developed lateral near the peduncle. Winged clusters have large cluster separated from the main cluster. A double eluster is formed if the wing approaches the length of the main axis.

[16] The Grapevine

Figure 5. Cluster shapes of grapes

Cluster Density: Cluster density implies to the amount of space between the berries. The density of the cluster is affected by several factors that include the size of the berries, the length of the peduncle and the structure of the lateral branches. A eluster is either loose or compact

Compact cluster: These types of dusters have short pedicles that are attached to short atcral branches, the berries are pressed tightly against each other, and it is difficult to pinch off individually. Such types of clusters have high probability for irregular colored berries and high incidence of bunch rot and poor shipping quality.

Loose cluster: In these types of cluster, the berries are separated from one another so that the air circulates easily between them and easy to pinch off individual berries.

Berry/Fruit: In grapevine, the fruit is referred to as berry, which is the edible part of the cluster. The shape, size, color, flavor, seed of berry are important factors that contribute to quality of grapes particularly tabic grapes.

B eny size: The size of a berry is an important feature that can be described in several different ways. It is a varietal character, but varies with the vigor of the vine, water absorption, berry set and degree of ripeness when picked. Berry size is determined based on diameter, volume and weight of berries as described below'.

[17] Asfaw Zelleke

Table 4. Berry size and other parameters categories

Diameter Size group (mm) Volume (cc) Weight (g) Small* 8-12 30-100 35-110 Medium* 12-18 101-300 111-330 Large** 18-24 330-650 331-700 Very large** >24 >650 >700 Source: Winkler ef al. (1974) *, ** Indicate varieties used for wine and table uses, respectively perry shape: the shape of berries is useful to distinguish between varieties. The six main berry shapes are briefly described and presented in Figure 6.

Spherical or round: Simple and most common shape of grapes Oblate: Berries that are more or less flat at both sides Ellipsoidal: Berries that are slightly flattened longitudinally; Ellipsoidal elongate Berries flattened longitudinally and further elongated. Ovoid or oval: Berries are flat on the bottom half with rounded top Obovoid: Top half of the berries have flattened sides with rounded base.

Spherical (round) Oblate Ellipsoidal

Obovoid Ellipsoidal elongated Ovoid (oval)

Figure 6. Main shapes of the vinifera berries

Berry color: Most varieties are uniformly green before first color. At verasion the color begins to develop and depending on variety will mature into a translucent white oi' blue black due to the type and relative proportion of a variable number (3 - 18) of

[18] The Grapevine anthocyanin (color pigment) on the skin of berries. Therefore, red berries have 3-6 anthocyanin while black varieties have from 13-18 anthocyanin.

Berry composition: The berries consist of skin, pulp and seed. The skin comprises 5 - 12% of the cluster (Amerinc and Joslyn, 1970). It has a bloom, which is a thin wax­ like layer. It enhances the appearance of the berry and prevents loss of water and mechanical injury. The skin also contains most of the coloring, aroma and flavor constituents. The pulp of berries is the part surrounded by the skin in which the seeds are embedded. According to Amcrine and Josyln, eighty to ninety percent of the crushed grapes are the juice. The pulp (flesh) of most grapes is translucent with colorlcss juice though in some varieties, the pulp is light or dark. The skin to pulp ratio is greater in smaller berries than in large ones. Thus, a ton of a small berried variety of grape would have more color and flavor than a ton of large seeded berry of same variety (Singleton, 1972).

Growth Processes of the Grapevines The growth of the grapevine can be defined as an irreversible increase in dry weight. The various important physiological processes during the growth period of grapevines are discussed.

Photosynthesis I involves the use of light energy by green leaves in transformation of CO2 and H20 into energy rich organic compounds. This is one of the most significant processes in the grapevine as it provides substrates/metabolites for subsequent metabolism in the grapevine. The process occurring through a number of intermediary steps is simplified as follows.

Light 6 CO2 +12 H20 + ------1------► C6H120 6 + 6 H20 + 6 0 2 Chlorophyll

These are two-step reactions involving the light and the dark reactions. The rate of photosynthesis can increase with light (up to a certain intensity) and under confincd situation by C 02 enrichment of the air. The light energy obtained from the sunlight drive four types of reactions in the chloroplast. These include photolysis of water or Hill reaction, where the water molecules are split into H and OH" (as chlorophyll absorb light), phosphorylation (formation of two high-energy molecules (ATP and NADPH), C 02 fixation and synthesis of carbohydrates. The first two reactions are carried out within the middle lamellae of the chloroplast while the second two reactions (dark reaction) are carried out in the stroma as action of soluble enzyme systems. The carbohydrates synthesized in the chloroplast (green cells) undergo scries of transformation and utilized as follows.

• Some are directly used as food in respiration and the stored energy is released for different metabolic activities;

[19] Asfavv Zelleke

• The unused food is translocated to storage tissues (fruits, roots etc.) and subsequently transformed into other forms of carbohydrate and organic substanccs. These materials arc further metabolized during the growth and development of the vines, depending on the relative needs at the different stages.

The rate of photosynthesis in the grapevine is affected by environmental factors such as temperature, CO:, light intensity and moisture. Some inherent factors such as age, variety, species and chlorophyll affect the rate of photosynthesis as well. The most important environmental factors arc discussed.

Temperature: The optimum temperature for photosynthesis by grape leaves is about 25"C. In case of vines grown under controlled environment, the maximum increase in dry weight occurred at temperature range of 25" - 29°C and declined rapidly above 30°C reaching zero at 451'- 50°C (Kricdman. 1968). According to Kriedman. die rate of C 02 assimilation decreases fast at temperature below 15°C and net assimilation of C 0 2 is near zero at 30°C.

Light: Light is one of the major factors influencing photosynthesis. In the absence of light, photosynthesis cannot take place. Hcnce, the light intensity required for photosynthesis of grapevines under optimal environment conditions (adequate moisture, optimum temperature and adequate nutrients) ranges between 2 500 and 5 000 foot-candle (1/4 - 1/2 of sunlight at noontime). The optimum light intensity is referred to the light saturation point. Light intensity above saturation point does not increase the rate of photosynthesis, but a steady increase beyond this point may have a negative effect on net photosynthesis (Kricdman. 1968). A decrease in light intensity T however reduces the rate of photosynthesis. According to Kriedman, at 122 foot candles, the rate of photosynthesis just equals the rate of respiration and the vines neither gain nor lose weight.

Water: Water is the major component of living plants. It varies from 92 - 93 in young roots to 90 - 95 % in young green plant material and to 86 - 90 % in fruit trees. In the absence of water, photosynthesis cannot take place. Thus in photosynthesis, hydrolysis of water is the basic and essential process that initiates an electron transport padiway transferring electrons from water to NADP - a chemical energy.

Respiration The breakdown of carbohydrate, a process in which 0 2 is involved is the reverse of photosynthesis. In photosynthesis, energy is stored while energy is released in respiration. The overall equation for the oxidation of glucose is indicated by:

C6 Hi20 6 + 602 ------► 6CO 2 + 6H20 + energy (686 kcal)

Respiration is therefore, the process of obtaining energy from the breakdown of organic materials. Most of the energy is channeled into chemical work for the synthesis of organic materials needed for growth and development of the vines. In the process, a small amount of energy is lost as heat. A number of factors affect the rate of

[20] The Grapevine respiration in grapevines. The most important ones are the age of tissues and temperature. Young tissues are metabolically active and develop rapidly than mature ones. The rate of respiration of young immature berries is 5 to 10 times greater than in mature fruits (Harris et al., 1971). Likewise, an increase in temperature can increased rate of respiration of living organisms. Studies have shown that for every 10°C rise in temperature the rate of respiration approximately doubles (Kriedman, 1968).

Transpiration Loss of water from plants in the form of vapor is referred to as transpiration. The amount of water required annually for normal growth and fruiting of mature vines varies from 15 to 50 acrc inch (or 102 nr) of water. The upward movement of water from the roots through the xylcm of trunk and shoot to the top of the plant and then to the atmosphere has been explained by a plausible theory of transpiration pull of water and cohesion theory (Salisbury and Ross, 1984).

Absorption oS Water 'The absorption force applied to the water in the xylem conduits leads to absorption of water by the roots of grapevines. Consequently, a continuous column of water is extended due to the high cohesion force of water from the roots to the leaves. Under normal conditions, water is pulled continuously into the root from cell to cell across the absorption zone and up the conducting (xylem) system to the leaves. During periods of high humidity or at night, transpiration is low and absorption of water exceeds transpiration. Under such condition, water is absorbed by osmosis thus leading to a pressure build up in the roots and then in the xylcm system and guttation may occur. Nonetheless, the mechanism of water absorption by the roots is the result of osmotic movement of water into the roots (Salisbury and Ross 1984). Such situation occurs only when the soil solutes accumulate in the ccll sap, thus lowering the water potential of the ccll sap. As a result, water moves across the concentration gradient and icnce into the cell from the soil solution. Consequently, a pull occurs in large volume during transpiration. Such a physical proccss of absorption helps in understanding how water requirement of the vines is largely met. However, the removal of water from the soil by root cells and its movement into the xylem system under pressure to producc ‘bleeding” (root exudates) that occurs after pruning is not clcarly understood. The time of bleeding may coincide with new root growth. Root exudates of grapevine contain cytokinins and gibbercllins (Skene, 1967) and under low temperature sugars may also be present in large quantities (Galstone and Davies, 1969).

Absorption of Mineral Nutrients The mineral nutrients in the soil are in solution, which enter into the roots of vines through the epidermal cells and root hairs. The ions enter the root cell indiscriminately by diffusion and absorption non-sclectively. The passive movement of ions into the roots in the soil solution along the xylem stream and then into the shoots is dependent upon the rates of water absorption and transpiration (Hylmo, 1953). The greater ion intake and accumulation in the leaves is in direct association with high rates of transpiration (Barton, 1955).

[21] Asfaw Zelleke

Ions also enter into the roots of vines by activc transport through the operation of a carrier system (Epstein. 1956), which is based on the attachment of the ions to carrier molecules. The carrier-ion complex enters the root cell barriers and then discharges the ion into the xylem cclls of the root. The free carrier returns to its initial position to repeat the active ion transport. The ions of the mineral nutrients move/translocate to the site/point of use along with the xylem sap. Finally, both absorption and active transport of ions of mineral nutrients are taken selectively since the cclls absorb some ions in much greater amount than others. According to Epstein (1956), K and NO; are absorbed several times as rapidly as Mg, Ca and SOj.

Translocation Translocation refers to the movement of water and mineral nutrient ions through xylem duct to the trunk, arms and shoots of vines. Similarly, photosynthate (sugar), litrogenous materials and organic acids arc translocated to the point of use through the phloem. In the xylem sap relativ ely large amounts of glutamine, malic acid, inorganic nutrients and small amount of sugars are transported (Hardy, 1969). Translocation of organic substances in the planr is affected by environmental factors such as temperature, light. CO2, moisture, nutrients, etc. Radial movement of water and food also occur in the vascular rays which arc storage tissues. Water and food materials moving upward in the xylem enter the ray cells and move across the stem to the phloem. Similarly photosynthates (food) moving down the phloem enter the ray cclls and arc carried to the xylem tissue or stored ( Essaw, 1965; Cutter. 1969).

Phenology Phenology of the grapevine refers to the different stages of the annual cycle growth r events of the grapevine. Like other fruit trees, the grapevine also has quite predictable annual growth cycle (McIntyre et a l 1982). The different stages of growth arc discussed.

Dormancy This stage of annual cycle of growth of die vine is fairly distinct in the temperate zone where vines shed their leav es before entering into the dormant period. In the tropical and sub-tropical regions where grapes are cultivated, the vines do not shed their leaves. In such areas, horticultural practices such as defoliation, root pruning, withholding water supply etc. are practiced to enhancc dormancy by stopping growth. These practices are done twice in areas where two crops per year are possible. Based on dormancy inducing factors, there arc two periods of dormancy. These arc quiesccnce and rest. The first type of dormancy is controlled by exogenous factors. Buds fail to grow because of unfavorable external conditions such as temperature, moisture, light etc. The second type of dormancy (rest) is controlled by endogenous factors in which internal factors prevent bud growth despite favorable external environmental conditions. The balance of endogenous growth hormones, inhibitor and promoter has been implicated as major factor responsible for inductions or release of dormancy, where the balance is weighed in favor of the inhibitor during the period of rest and at termination of rest, the reverse appeared to be true. Emmcrson and Powell (1978) and Seeley and Powell (1981) have nullified this conclusion because of the

[22] The Grapevine level of inhibitors was found to be much higher during the active growth period than at the period when the plants were under rest or dormancy condition.

Bud Break: The period when the dormant bud begins to swell and the green shoot emerges is referred to as bud break. The shoot, which consists of leaves, tendril, cluster and new buds in the axils of a leaf develops rapidly following the normal growth pattern curve of a plant. The new bud could be fruitful or unfruitful, subject to the influence of certain factors. Some of these factors are discussed in brief.

Age factors Age of vines affects fruitful bud formation. Older vines grow rapidly and accumulate more carbohydrate materials to foster bud differentiation and produce more fruitful buds compared to young vines.

Carbohydrate accumulation: The dircct role of carbohvdratc in the formation of fruitful bud is not entirely clear. The percentage of starch in the cane is closely associated with fruitful bud formation. Accumulation of carbohydrate in the grapevines, however, is not uniform along the shoot, and thus it is most rapid in the mid-section of the shoot where fruit bud differentiation first occurs most rapidly.

Nitrogen supply: Excess of nitrogen was found detrimental to fruit bud formation. However, the time and rate of N application do not show considerable effect on bud behavior.

Carbohydrate/Nitrogen Ratio Low carbohydrate/nitrogen ratio: This implies a moderate carbohydrate and high nitrogen contcnt in tissues, which is typical of young vines. Under such condition, strong shoot growth (large leaves, long intcrnodes, late growth, and poor wood maturity) and little or no fruit formation arc most common

High carbohydrate ratio: Vines that have high carbohydrate and moderate nitrogen in the tissues manifest normal shoot growth (normal size leaves, average intcrnodcs growth, good wood maturity) and abundant fruit bud formation.

Very high carbohydrate ratio: Vines with very high carbohydrate and low nitrogen content have poor vegetative growth with limited fruit bud formation.

Other nutrients: The relationship of the other nutrients and fruit formation is not clearly understood, although several reports suggest a role for P in flowering. In Lisbon lemon, P applications have increased flower formation; whereas, N was found to reduce it. Fruitful bud has been increased in the grapevine by the application of zinc in areas where little leaf is a serious problem. Little leaf may be implicated with reduced synthesis and accumulation of carbohydrate, which may affect the balance between the carbohydrate and nitrogen content, and consequently fruit bud formation.

Water supply: A temporary reduction in soil moisture may check the growth of vines, which subsequently favor the accumulation of carbohydrates. This condition

[23] Asfaw Zelleke may stimulate fruit bud formation if the nitrogen supply is adequate. If, however, the soil moisture is depleted to the wilting point, fruitful bud development will be reduced.

Temperature and light intensity: Bud fruitfulness is directly related to the temperature around the bud or to the maximum temperature, die vines reccive daily. Heat summation also affect the number of bunch primordia per bud with increasing light intensity (900-3,600 foot-candles) and fruitfulness of new bud depends on the daily duration of high light intensity but not on the length of the uninterrupted dark period (Kriedman, 1968). Light intensity falling on the bud itself, also influences bud formation rather than the whole plant illumination and total photosynthate. Nevertheless, the mode of action of temperature and light intensity for fruit bud formation has not been clearly elucidated.

Cultural practices: It is a well-established fact that the training system of vines has 1 marked effect on bud fruitfulness. Bud fruitfulness increases considerably when the exposure of the vine's leaf surface to light is improved. Defoliation, shading and girdling could affect the formation of fruitful buds largely through their effect upon the accumulation of carbohydrate and synthesis of other organic substances. ftloom: The opening of the inflorescence or the fall of the calyptra (cap) from the llowers usually take place about 50-60 days after bud break. It is about 63 days under Debre Zeit condition. The duration depends on weather conditions. Cool moist weather delays blooming while bright warm weather facilitates earlier blooming. This period is of particular importance because it marks the process of flower bud initiation for the following year's crop. The development continues until harvest time. Full bloom is the time when over 50 % of the petals have fallen from the flowers.

Pollination and fertilization: When the caps fall from the flower, pollen grains are released from the stamens (anther). They fall on the stigma and germinate under favorable conditions. A pollen tube grows down the style into the ovary (embryo sac) through which two male gametes reach the ovary. One of the male gametes will unite with the egg ccll to form the zygote and then the embryo. The second male gamete units with synerged cell to form the endosperm. The unfertilized pistil and some impotent berries, about 60 % shatter from the cluster. This is natural thinning of dusters as it keeps cluster size normal or less compact. Cluster of some varieties may set poorly and may have many small seedless berries (shot berries) that fail to enlarge. This is a condition known as millerandage (W'inkler et al., 1974), which may be caused by frost or rainy weather at bloom time. In seeded varieties, under normal conditions, berries may contain 0 to 4 seeds. There is a direct relationship between the number of seeds and the size of berries. The greater the numbers of seeds, the larger will be the size of the berry. This is because the seeds arc the potential sources of growth hormones. Gibbcrellins and other growth hormones produced by developing seed, promote berry growth as they diffuse or enter into the flesh of the berry. Some varieties of grapevines are parthenocarpic. They set fruit without fertilization. Some varieties (Black Corinth) however do require stimulus of pollination per fruit set and development and hence the phenomenon is referred to as stimulative parthcnocarpy. In

[24] The Grapevine some other varieties (Thompson Seedless) although fertilization docs occur but the embryo degenerates or aborts. This process is known as stenospermocarpy.

Fruit setting: This is the stage of growth following bloom leading to berries retention on the cluster. Weaver (1976) indicated that fruit set and development are probably controlled by an interaction of growth hormones such as auxin, gibberellins, cytokinins, ethylene and inhibitors (abscissic acid).

Anthesis Time ------>»

Figure 7. Grape berry growth and development

The normal growth of grape berry has two distinct stages based on changes in color, shape and composition. This includes:

Green berry growth: This stage is from fruit setting to change in color and composition (verasion) and corresponds to beginning of stage III. The berries are firm and their size tend to increase rapidly. The level of the acids (mainly tartaric and malic) is high and the level of the sugars is low.

Ripening of berries. Berry ripening occurs at veraison when fruits start to develop color and the texture softens. In the white varieties this stage is characterized by change in color with green berries turning to yellowish white or white. In pigmented

[25] Asfaw Zelleke varieties, the color becomes more intense as ripening progresses. At maturity the level of sugar increases followed by a marked decrease in acidity. The time of ripening of berries on the eluster varies. Berries on the distal end of cluster mature rapidly as compared to berries at the proximal end. The rate of ripening is usually governed by weather conditions. Ripening is more rapid under warm dry weather than in cool moist weather. Over ripening of fruits is required to be avoided sincc over ripe fruits are easily attacked by diseases and insect pests subsequently losing economical value.

Harvesting: Well ripen grapes are harvested in the summer (northern hemisphere) time and in January and June (in subtropical regions). However, despite the range in time of maturity or harvest, the physiology, morphology and chemical development of the grape berry remains the same. Thus, the development of the grape berry is a sequence of changes in the physiology and chemical composition of berries.

Physiology and chemistry of berry development

F’hysiology of berry development The subsequent growth and development of berries in seeded varieties shows an increase in volume, fresh weight and dry weight and diameter if plotted as a function of time exhibiting a double sigmoid curve (Figure 7). The situation with seedless (parthenocarpic) varieties is however different in that the seedless berries show less distinguished growth period (Winkler et al., 1074). They show no or little trend of double sigmoid growth pattern. In the successive sigmoid growth pattern there are three arbitrary growth stages. Hence, Stage I (45 - 60 days) is the initial phase of rapid growth; Stage II (8 - 24 days), the lag phase, which may be less distinct in seedless cultivars than in seeded cultivars, of slow or no growth stage; and Stage III (45 - 60 days) is the final stage of resumed growth and maturation. These three Stages of berry growth are briefly discussed.

Stage I This stage is designated as the vegetative phase. Following set, the berry increases in sze and mass. The developing berries have high chlorophyll content. They arc characterized by the growth of the seed and pericarp with little embryo development. The green hard berries accumulate organic acids, which are commonly measured as titratablc acidity (TA)

Stage II This sage is characterized by slow growth of the pericarp and by seed maturation. A decrease in chlorophyll content and rate of photosynthesis and respiration arc distinct. Metabolism is slow and embryo development is rapid. The berry remains hard and green until the end of the stage. The duration of the lag phase normally determines vv hcthcr a cultivar is carly-or late maturing.

[26] The Grapevine

Stage III This stage begins at verasion which makes dramatic changes in berry softening and in color change in pigmented cultivar. The resumption of rapid growth during this period is due to cell expansion. It is during this stage that the berries attain their maximum size and ripen. Consequently, the titratable acidity decreases and a massive accumulation of hexose sugar occur. Maxic and Crane (1968) have postulated the role of ethylene in initiating the growth in stage III. The amount of sugar accumulated by berry varies with berry size ranging from 5 mg per day in small berries and 50 mg per day in large berries (Kliewcr and Antcliff, 1970).

Chemistry o£ Berry Development Berry development is a result of accumulation and metabolism of a range of compounds, which arc affected by several factors. Shoot growth vigor, crop load and crop exposure affect the composition of grape berries. High crop load has a management effect in lowering the °Brix and content of flavor compounds (Singlton, 1975). According to Singlton, variation in the amounts of these compounds (grape composition)- directly determines wine quality.

Berry composition The berry is composed of organic and inorganic substances. The most important ones are discusscd.

Water: The major component in the berry is water, an inorganic substancc. Its amount closely parallels berry volume, which is usually determined by daily increments of inflow (phloem water) balanced with outflow (xylem water) (Lang and Thropc, 1988).

Sugar: '/he majority of soluble solids (90%) in grape juice is sugar (Singlton, 1975). The remainder consists of organic acids, proteins, polysaccharides, potassium, pectin, etc.). Glucose and fructosc make up about 99% of the sugar. Glucosc increases in concentration during ripening. At harvest about 25 % of the berry weight consist sugar. \ t verasion glucose cxceeds fructose concentration. As sugaring proceeds, the ratio glucosc to fructosc tends toward unity. In over ripe grapes the metabolism favors ormation of fructosc and the ratio (fructose/glucose) exceeds unity.

Organic Acids: Tartaric and malic acids are the major acids in grapes. They comprise over 90 % of the total titratable acidity. Grape berries arc large accumulator of acids during the first growth cyclc and they arc the predominant component of the berry by verasion. Tartaric acid is stronger, more stable and at high concentration than malic acid. It is accumulated during early berry growth while malic acid is accumulated strongly as verasion approaches (10 - 20 g/1) often higher than tartaric acid. After verasion tartaric acid declines and this could be attributed to dilution by water as a result of berry growth, and conversion of acids to salts.

Vitamins: The vitamins do not affect the time or methods of harvesting grapes even though they influence vcast metabolism during fermentation. The amount of vitamins

[27] Asfaw Zelleke in the grape is not larae but most vitamins increase with ripening (Winkler et al.. 1974).

Nitrogenous compounds: Ammonium is the predominant form of N in immature berries but decline as ripening progress. In ripe grapes, amino acids make up more than half of the total N, in most of them being formed during the latter half of ripening with proline, argenine and glutamine often predominating (Kliewer and Cook, 1974). The level of amino acids is to be affected by variety, climate and growing conditions (Kliewer, 19^1). Changes in the chemical composition of berries/fruits take place during ripening. Sugar accumulation commences at verasion. The concentration of sugars increases steadily during ripening but the rate of increase is affectcd by water supply to the vines. Low water stress favors acceleration of sugar accumulation while rain or irrigation decelerates it or even causes a temporary reduction (Smart and Coomb, 1971). Malatc decrease with ripening due to respiration, while K increases (Coomb, 1987). Flavor volatiles and some amino acids accumulate later in ripening when sugar content lowers.

[28] The Grapevine Chapter III

Propagation

ccds, cuttings, budding, grafting, layering or tissue culture could propagate the grapevine. Sexual propagation is not a preferred practice exccpt by the breeders becausc the seedlings may differ appreciably from the parents and from each other arising due to genetic variation. They are also inferior in vigor, fruit production and quality as compared to the parent vines. Sexual propagation is valuable to develop new varieties. The commonly adopted asexual methods of propagation in different grape growing regions are briefly discussed. Hardwood cuttings made from the section of matured canes (previous year's shoot) should be used. The various techniques involved in the preparation of cuttings are described below.

Selection of Canes for Cuttings Canes that are vigorous and well matured with ample supply of stored foods should be selected. Cuttings made from such canes could nourish the developing roots and shoots until new plants become self-sustaining. Cuttings perform poorly if taken from vines that have been water stressed or defoliated by insects or diseases before the wood has matured. The basal and central parts of a cane make the best cuttings; those made from the tip portion of canes grow weakly (Winkler et al., 1974). Cuttings of about 13 mm n diameter and medium internodes arc commonly used. Cuttings with long intcrnodes though form rapid growth often have low stored reserves. Cuttings should be made promptly after the vine is pruned off Use of dried canes is not advisable, as they will not root. In addition, using canes, which arc flattened or immature or have dead sections, should be avoided. The nutritional status of the mother vines is also mportant. Cuttings from vines receiving high nitrogen fertilization may root poorly. However, high level of N, P, K and Zn resulted in good rooting percentage (Weaver, 1976).

[29] Asfaw Zelleke

Preparation o£ Cuttings Cuttings could be taken at any time of the year during the dormant period. Cuttings for own rooted vines or scion wood arc usually made 30-40 cm long. This length may vary slightly, depending on the propagation method adopted.

Rootstock cuttings are usually made longer (40-45 cm) so that when grafted the graft union remains above the soil level. Except the cop bud. all the other buds are removed to facilitate the development of strong shoot from a single bud. A top cut of 2-3 cm above the top node is made by sloping away from the top bud and the cut at the base should be straight across just below a node (Figure 8a). Preparing cuttings in such a manner would enable workers to identify the top (sloping end) and the bottom (Shorter/flat end) an error most often committed in some vineyards. Moreover, the shorter or no wood left at the bottom of the bud facilitates formation of root system. Cuttings arc usually tied in bundles of 50 or 100 with string or polypropylene twine or similar materials and variety indicated using plastic label. The use of proper pruning s.iear (Figure 9) is unequivocal.

Figure 9. Pruning Shear

[30] The Grapevine

Treatment and Storage Cuttings required for an open ground nursery may be buried (stored) in a moist medium to allow callusing to proceed or they may be stored in a cold room. Those requiring bench grafting or as scion wood for budding are normally stored in a cold room. Most growers, depending upon length of storage period and prevailing problems in the regions commonly practice two kinds of treatment of cuttings viz., hot water and chinosol treatments.

Hot water treatment Hot water treatment is the cheapest means of destroying soil borne pests and diseases of cuttings. Cuttings arc immersed in hot water for sufficient duration to kill pests and diseases. The temperature should not be high to avoid plant tissue injury. Temperature of 50°C for longer than 10 minutes may inhibit callusing and can cause thermal death of cuttings. Hot water treatment can be used to inactivate many of the soil borne diseases and pests. Cuttings should be immediately dipped in cold water following hot water treatment.

Chinosol treatment Chinosol (8-hydroxy-quinolinc sulphate) is water-soluble chemicals used as a protection against the grey mold (Boirytis cinerea). It is found superior to other materials in its ability to penetrate the bark of cuttings and kill fungal and bacterial diseases (Becker and Hiller. 1977). Bundles of cuttings arc first soaked in clean water for a day or two until they sink. They are then soaked in a 0.5% Chinosol solution for about 4 hours. Longer soaking for 15 hours at 10-20°C is commonly recommended. Chinosol treatment is not as simple and inexpensive as that of hot water treatment, "reatment however becomes most effective when cuttings are stored at very low temperature. Cold storage has the advantage in that the metabolism of cuttings is slowed down and carbohydrate reserv es are conserved. However, if the temperature alls below zero, icc may form and the Chinosol concentration may assume toxic evcls. Chinosol treated cuttings can be heat-sealed in polyethylene bags to prevent desiccation. Under such conditions, cuttings can be stored in a cold room and may still be viable beyond one year.

Callusing In some situations, cuttings can be held in a cold room and planted out when the soil is warm enough. In Ethiopia, it is not a common practicc to callus cuttings before planting as is usually done in other grapevine growing countries. An efficient method of callusing is to dig a trench about 50 cm deep in a well-drained sandy soil, place the bundles of cuttings vertically in it and fill the trench with soil. Then, the cuttings are covered with 5 cm of soil and watered occasionally. Cuttings can also be callused above ground in a container of moist, washed, sand or hard wood sawdust. If callusing of stored cuttings is delayed, it may be advantageous to callus cuttings upside down to inhibit shoot growth and hasten callus development with the warmth attained about 5 cm below the surface of the sand or sawdust. When callus and root initials have developed, usually within weeks, the cuttings are removed from the callusing bed and

[31] Asfaw Zelleke planted. Cuttings can be planted directly in the field or in nursery beds and transplanted in the field later on. Cuttings could be produced on own roots and/or on grafted/budded rootstock depending on growing conditions, availability of rootstocks and the knowhow of the grafting techniques

Nursery Propagation Onc-year old rooted cuttings (Figure 8b), arc produced in an open ground nursery. The :ime could vary from 6-12 months depending on the location. The procedure involved in the selection of nursery site and preparation arc as detailed below.

Choosing nursery site A deep friable, fertile sandy loam, well drained and free from insect pests and diseases is an ideal nursery soil. The site should be level, well protected from the wind and accessiblc to good quality irrigation water. The use of new sites every year or land that has been fallowed for several years, will reduce the problems of soil-borne insect pests and diseases and soil problems of infertility.

Nursery site preparation rhc nursery site is ploughed well to a depth of about 30 cm. The sub soil should not be raised. Disc harrow or rotary-hoe may be used to bring the soil to a fine tilth. Fumigation of the soil with appropriate fumigant is helpful, if soil -borne diseases are expccted. A meshed-wire fence about 1 m high may be erectcd to protect against rodents and wild animals. If the site is windy, it may be necessary to establish windbreaks.

Production of Own Rooted Cuttings of Fruiting Cultivars A vineyard of own-rooted vines can be established by direct planting of cuttings provided, conditions are favorable i.e., a warm well-drained soil, adequate water, weed control and freedom from insect pests and diseases. However, because of a risk of low take off, one-year-old rooted cuttings (rootings) are normally preferred for planting. In Ethiopia, own-rooted cuttings (Figure 8c) in an open ground nursery are used to propagate grapevines. This is the procedure commonly adopted. Even though there is variation in the development of roots, cuttings of most varieties root readily. Depending on location, it takes 6-12 months to develop matured rooted cuttings. In general, cuttings arc planted immediately after preparation, if cold room facility is not available. Planting of at least 25 % more cuttings than the actual number of rooted cuttings required is essential. A row spacing of 1.2-1.5 m is suitable to allow a normal o Deration. A furrow is opened along each row and water is applied along the full length of the furrow. The cuttings are pushed into the soil leaving a single node exposed. It is also a common practice to grow' cuttings to full length covering the top end with fine soil. Cuttings can be planted 5 cm apart, but a wider spacing may be preferable for irfertile soils or in case, irrigation is limited. While planting different cultivars they should be separated by gaps with proper labels in order to avoid mixing up of cultivars during lifting of rooted cuttings. Field plan of the nursery should be made available in

[32] The Grapevine order to help identifying the proper location of each variety and avoid mixing of them in case labels arc lost.

Proper Nursery Management

I rrigation Adequate and good quality irrigation water free from dissolved salts is the most important factor required during the growing season. The soil should be maintained ciose to field capacity. Regular irrigations are needed during the early part of the growing season, especially if the weather is hot and dry. Any one of the different irrigation systems can be used provided facilities arc available. Furrow irrigation is commonly used if the slopes and length of furrow are satisfactory. On steep slopes, the length of furrow should be shorter.

Weed Control Weed control is essential as weeds compete for water, nutrients and sunlight. They also impede the lifting operation of rooted cuttings (rooting). Weeds arc routinely controlled by hand hoeing or by use of a garden rotary hoe. The size of the nursery usually determines the use of herbicides. Wider spacing favors for the use of herbicides.

Fertilizer Application Grapevine nurseries may require little fertilizer, if the soil is fertile. On less fertile sandy soils, small quantities of urea or ammonium nitrate can be applied regularly during the growing season, but application should be stopped after 4-5 months to allow shoots to harden.

Pests and Diseases Control The same insect pests and diseases of vineyards also attack the nurseries. Both powdery mildew and downy mildew infections are favored by the crowded plantings in Jic nursery. Chemical spray (Bayleton wp and Ridomil Gold, respectively) should be applied under predisposing conditions and regularly followed thereafter, depending upon weather conditions.

Proper Handling of Own Rooted Cuttings

Lifting Well-developed rooted cuttings (Figure 8b) could be lifted and transplanted any time of the year, provided irrigation water is available. In the highlands, they are transplanted in June just before the main rainy season. Lifting can be done manually with hand hoes or with a U-shaped digger fitted to a tractor to facilitate the lifting operation. In this case, roots are cut after lifting the rooted cuttings with spades. The tops may be pruned back before lifting. Each variety should then be bundled and labeled to avoid mixing up of varieties.

[33] Asfaw Zelleke

Grading Well-rooted cuttings should have several major roots spreading in all directions. Inferior quality should be rejected. Roots and shoot sprouts should be trimmed to facilitate bundling, but root pruning should not be excessive sincc it may rcducc initial establishment in the vineyard. Canes can be primed back to one or two well-placed 2- nodc spurs so that the rooted cuttings are ready for planting.

Storing Ideally, rooted cuttings should be planted immediately after lifting. They may be however kept for a day or two stacked in shade under cov er and the roots sprinkled with water frequently to prevent them from desiccation. Rooted cuttings may be stored for longer periods provided the bundles are heaped in a pit of moist sand or in a sandy soil location. The sand should be washed thoroughly between the roots and kept moist .intil the rooted cuttings are removed for planting. They can also be soaked in chinosol solution (0.1%) for about 15 hours and stored in sealed plastic bags at 1°C. Under diese conditions, the rooted cuttings can remain viable for as long as two years since rhey still contain sufficient carbohydrate reserves. In areas where nematodes are expected, it is possible to disinfect rooted cuttings by treatment with hot water or ncmatocidcs. Root knot nematodes are destroyed by submerging dormant rooted cuttings in hot water at 48UC for 30 min or 52°C for 5 min or 54°C for 2 min albeit nematocidcs (Fenamiphos at 100 mg/1 held at 25°C for 30 min) may be more effective than hot water treatment alone (Lear and Lider. 1959 as citcd by Winkler et al., 1974).

Production of Rooted Cuttings of Rootstock Rootstock cuttings are grown in a nursery using similar method as for own-rooted vines. However, prior to callusing, rootstocks cuttings should be re-cut immediately below the bottom node and disbudded leaving only the top one or two buds. The cuttings are dipped in 200 mg/1 indolcbutyric acid (IBA) solution at this stage and then allowed to callus. It is necessary to callus rootstock cuttings upright in damp hardwood sawdust. In the case of bcnch grafts, the planting of rootstock in an open-ground nursery should be delayed until the soil temperature at a depth of 20 cm reachcs lS^C. In the first year, rooted cuttings may be trained to a single stem or allowed to sprawl depending upon the method of budding or grafting to be used.

Budding and Bench Grafting in Nursery Bed T he budding of rootstocks in an open ground nursery is widely used to produce grafted vines. The various aspects of this procedure arc:

Budding Budding is the transfer of buds or bud stick (chip) from fruiting varieties /cultivars (the above ground part) to rootstocks (the underground part). Budding in the nursery bed is a common practice. Rootstocks should be vigorous and have high moisture prior to budding. Avoid budding in very hot or windy day to control bud desiccation. Scion woods of the fruiting variety may be held in fresh water or in icebox. It is cut with a

[34] The Grapevine budding knife; a matching is made in the stock and the bud is inserted so that the respective cambia arc brought in close contact without leaving gap. Then, the bud is tightly wrapped with budding tape to provide high humidity around the union and ensure close contact between stock and scion. With most budding techniques, the top portion of the stock is removed after the scion bud begins to grow. In the nursery, the most commonly used methods are chip budding (Figure 13) and T budding (Figure 15). These two methods are well dcscribcd under their respective sub-titles.

E*ench grafting A bench graft involves grafting single bud scions onto rootstock cuttings. As the name indicates, it is done indoors using dormant wood instead in the field. Bench grafting is the most commonly used for grafting vines throughout the world as it is the most suited one for mass production of grafted vines. The application of this method in developing countries is however, limited because of facility and traincd-workcr requirements. The typical method however, is briefly discussed.

Preparing scion wood and rootstock

Cuttings are stored in the cold room until they are ready for use. Prior to use they arc soaked for 1-5 days in sodium hypochlorite solution (2 mg/1 of water). Soaking of cuttings helps to remove chinosol, which otherwise can inhibit graft callus formation at ligh concentration and retards root development in many rootstock varieties (Becker and Hiller, 1977). Hot water treatment of rootstock cuttings can also be adopted at this stage. The rootstock cuttings arc disbudded with special disbudding knife in order to minimize the risk of suckering problems in the vineyard and re-cut as close as possible to the bottom node. Scion wood is then cut into one-node pieccs about 5 cm long with less than 2 cm above the bud. Stock and scion cuttings are held in buckets of chlorinated water prior to grafting. The stock and scion cuttings are usually grafted with an omega cut machine. Some growers in developed countries commonly practice application of an indolebutyric acid (IBA) treatment to the base of the grafts at this stage. IBA a synthetic auxin often used to enhance root formation on hard woodcuttings of such plants like the grapevines. The completed grafts are packed v ertically in a callusing medium in boxes, leaving a layer of medium below and at the top of the grafts at exactly the same level. Shade cloth is placed on top of the grafts, which in turn is lightly covered with moist Perlite or Vermiculitc. Various box sizes may be used to hold 200-300 grafts. The boxes are lined with plastic sheet. A suitable callusing medium (Perlite, Vcrmiculite, pcat/Perlite or sterilized sawdust) providing ligh relative humidity around the union is used. The medium must not be too wet. The boxes of grafts may be kept at 1°C for several weeks until ready to transfer into callusing room.

Callusing The boxes containing the grafts are placed in a callusing room held at 28-29°C for about 2 wrceks until a complete ring of callus 1-2 mm thick develops at the union. Excessive callus formation at the union should be avoided as this may result in

[35] Asfaw Zelleke unevenly differentiated vascular tissues. As the shoots begin to grow, the shade cloth and medium above the graft may be removed and the boxes placed in a heated glasshouse to allow the shoots grow in light. This will avoid etiolation by allowing photosynthesis to commence. The grafts are misted daily with chlorinated water and sprayed weekly with a fungicide to control Botrytis infection. The glasshouse temperature should be held at a minimum of 16-20°C and a maximum of 28°C for 4-5 days. Following this, the grafts arc hardened-off for about 7-10 days by moving them firstly, to a shade house then outdoors prior to planting.

Waxing and Planting in the Nursery Grafts arc removed from the callusing boxes and the shoots are trimmed, if too long. Then they are dipped in a grafting wax held at 7()_“5°C. Grafts should be dippec; into cold water immediately after waxing to cool them down. The basal portion of the grafts can then be dipped in a fungicide as a protection against pathogen attack. The grafts arc then planted in an open-ground nursery 5-7 cm apart, with 1.2-1.5 m between rows. Grafts should be planted and immediately watered. The union should be ocatcd at about 5 cm above die soil. It is essential to check and discard unsatisfactory grafts before planting. Grafts can also be planted in pots and grown under shade, but vines produced in this way may not be as strong as vines produced in open-ground nursery. Usually, the success of bench grafting is affccted by a number of factors according to Hartman and Kestcr (1975). These include:

• adequate facilities. • skilled workers, • good compatibility between stock and scion, • good contact of cambium layers of the scion and stock. • favorable environmental conditions such as moisture, temperature and aeration, and • the conditions of stocks and scions (young parts are relatively successful in grafting).

Field Propagation

]

Top working Grapevines under optimum culture require three to six years to reach full economic production. However, changes in demand may occur over a shorter time, leaving the grape grower with a variety in little demand replacing being costly. One solution to this situation is to graft or bud another variety on top. This procedure is known as top w'orking or top grafting. Many methods have been used to top work grapevines. The

[36] The Grapevine type to be adopted is generally determined by the size of the stock. The most common tv-pes arc briefly discussed

Grafting Grafting is the art of combining two pieces of living plant tissues together in such a manner that they will unite and subsequently grow and develop into one plant. The part of the graft combination, which is to become the upper portion is the scion and the part, which is to become the lower portion with root system is the rootstock. The main reasons of grafting grapevines are:

• To obtain vines of a fruiting variety with root system tolerant to soil-borne problems viz., inscct pests (Phylloxera, nematodes) and diseases; ® To develop vines tolerant to certain soil conditions (salinity, alkalinity, low pH, etc..); • To change poor fruit quality, susceptible 10 diseases, etc., of existing varieties.

Grafting knife (Figure 10) is used in grafting grapevines. Different methods are employed in field grafting and each method is described here.

Figure 10. Grafting Knife

Whip grafting Whip or tongue grafting is useful for smaller materials with a diameter of 0.5 - l .5 cm. "he scion and the stock should be equal in diameter. It is highly successful if properly done because the cambium contacts are better and more reliable. It heals quickly and makes a strong union. The scion contains two to three buds with the graft union made in the smooth internodes area below the lower bud.

[37] Asfaw Zelleke

Figure 11. Whip or tongue grafting

The cut made at the top of the stock should be the same as those made at the bottom of the scion (Figure l la and b). Two cuts arc made. First, a long, smooth sloping cut is made 1.5 - 5 cm long using a sharp knife. The cut is started downward at a point about one-third of the length of the first cut. The second cut should be made following along under the first cut tending to parallel it. Then, the stock and the scion arc inserted into each other with the tongues interlocking. It is important that the cambium layers matchcs along at least one side but preferably along both sides. After the scion and stock arc fitted together, they should be held securely until the pieces are united. The most common method is to wrap the unions with budding rubber or raffia or waxed string (Figure 11c). After wrapping the scion-stock (SR) union can be covered with grafting wax or by burying the graft in moist sand, peat, or moss.

Cleft and notch grafting

•Cleft graft: This is most widely used method of grafting. It is useful in grafting branches of about 3 - 10 cm in diameter and that can split easily. Cleft grafting can be done any time during dormant season; but the chance for successful healing of the graft union is best if the work is done when the buds of the stock arc beginning to swell or just before activc growth started. In preparing the stock for cleft grafting, it is important that the branch sawed off is smooth-grained, free of knots and about 15 cm long. A special cleft grafting tool or butcher’s knife is used to make a vertical split about 5 - 10cm down in tangential direction in relation to the ccnter of the stub. Hammer or mallet is used to pound the knife into the stock. As a result, a good straight split will be made and a screwdriver can be driven into the top of the split to hold it open to insert the scion.

A scion, containing tw'o to three buds, is cut with a sharp knife in a wedge form. The basal end of each scion is cut into a long gently sloping w;edge with the outer side of the wedge slightly wider than the inside edge. The length of the scion should be the same or equal to the length of the cut (10 cm) on the stub. The number of scion to be

[38] The Grapevine inserted into the split depends on the size of the v ine. Usually, one scion is used if the diameter of the vine is less than 2.5 cm; but two scions are preferable for larger vines (Figure 12A2). The scion is now ready to be inserted into the split on the stub. The scion and the stub should be tied together with a string around the top. When the shoots arc well developed, the weaker once should be removed leaving only one strong shoot.

Notch grafting; It is also called Saw Kerf or wedge grafting (Hartman and Kester, 1975). Notch grafting can be used in placc of clcft grafting on branches of about 5-10 c n or more in diameter. The method is successfully used with certain species that arc difficult to graft. It however requires skill and hence difficult for beginners to perform than most of the other types.

In this method, a stub is prepared by sawing off the stem/branches of the stock. A narrow V shaped notch is made with thin-bladcd and fine-toothed saw on the side of the stock about 10 cm down on the side of the stub and 2 -4 cm toward the centre of the stub (same diameter of the scion). The notch tapers at the bottom. Using a sharp knife the saw cut (notch) is widen to fit the scion. A cut is also made at the bottom of the cut and a wedge piece is knocked out with a screwdriver to form V-shaped notch.

The scion cut should be about 10 cm long and should contain 2 - 3 buds. It should be shaped in a similar manner as the cut on the stub. The basal end should be cut to a wedge shape with the outside edge a little thicker than the inside edge. Then, it should be inserted into the cut on the stub in such a way so that the cambium of both the scion and the stock coincide or fit together. After the insertion, the scion should be held firmly in place until the tissues grow together. Finally, the cut surface of the graft union should be thoroughly waxed to avoid entrance of microorganisms.

This type of grafting can also be made in a much simpler way. A “V” cut about 2.5 cm long is made straight into the stock to a depth equal to the diameter of the scion. Two cuts are made on the stock using a heavy knife pounded in with plastic tip hammer. The wedge piece is knocked out with a screwdriver. A simple “V" shaped wedge scion is also made and inserted into the stock. The cambium layers should match to ensure good contact. If the graft is properly made, the scion should fit tightly without railing (Figure 12B2). The exposed cut surface should be thoroughly waxed.

[39] Asfaw Zelleke

Scion-Stock United

B

Scion-Stock United

Figure 12. Cleft grafting (A) and notch grafting (B)

Field Budding

Chip budding Chip budding is the most commonly employed practicc in budding small materials (< 2 - 2.5 cm) of grapevine when the bark is not slipping (Alley, 1979). The buds from canes arc removed first, by making deep cut into the bud-stick starting just below the bud and then moving downwards at an angle of 45°. A second cut is made starting at :ibout 1 cm above the bud, sliding the knife downwards in a straight plane behind the bud. A wedge shaped chip (15 mm long) is removed as the second cut reaches at the surface of the first cut (Figure 13b). Similar cut. but more acute is made on the side of :hc rootstock above the ground level. The chip is removed from the stock and replaced oy the one from the bud stick. If they have been cut to the same size and shape - as ihey should be - a good fit is obtained. The scion chip should be placed in the notch (Figure 13d) matching carefully the cambium layers of both the scion and the ootstock preferably on both sides of the stem (but, at least on one side). Tie the chip n place with budding rubber strip or plastic tape. Make two or three wraps round the :op end of the bud to hold it firmly in placc (Figure 13e). The tie is then finished with a spiral of two or three turns, round the tip of ihe stock, over the base of the bud, and finally waxing it. Chip budding has given excellent results in budding grapevine cultivars on phylloxera or nematode-resistant rootstock (Ball, 1972).

[40] The Grapevine

a-b = chip bud is cut from scion wood: c = matching cuts are made in the stock:, d-e = the chip bud is inserted and wrapped with tape.

Figure 13. Chip budding

Figure 14. Budding Knife

T>budding or shield budding T-budding: it is usually done on mature vines (Alley, 1977; Hodge and Bass, 1989). It is not satisfactory on shoots of grapevines under 2.5 cm diameter. The bark of young vines is very thin and tears easily when the bud is inserted under the bark. The first step in T-bud grafting is to decapitate the vine at about 90 cm above the ground. Loose bark should be removed from the working areas, where the incision is to be made. Using a budding-knife (Figure 14) vertical cut of 2- 5 cm long is made at about 2 cm below the top. Horizontal cut across the top of the first cut is made completing the T cut. The bark corners arc pulled open gently with the high point of the knife blade for the bud insertion. With a bud stick about 1 cm in diameter, a horizontal cut is made into the stick, from 2 cm above the bud and 2 cm below the bud. Downward cut

[41] Asfaw Zelleke on both sides of the bud starting from the top horizontal cuts to the bottom is made. The bud from the stick is carefully extracted and inserted deeply under the open corners of the bark of the stock and the base of the bud shield pushed well below the bottom of the vertical cut with the point of the knife blade (Figure 15). The bud is covered with tightly pulled, overlapping wraps of plastic tape starting below the bud and wrapping up to about 3 cm above the horizontal cut (Figure 15f). The final wraps are brought down to just above the bud, tied by taking the end of the tape under the last wrap, and pulled tightly to stretch the tape. The tape will hold the bud tightly in place, and it will prevent the new developing shoot from breaking away. This method is also known as shield budding. The T-bud designation arises from the T- like appearance of the cut in the stock. The shield-bud name is also derived from the shield like appearance of the bud piece when it is ready for the insertion in the stock.

A shield bud is cut from scion wood (a); A ' T" cut is made on the stock (b & c); The bud is inserted in the T cut and wrapped with tape (d - f). Adapted from Hartman and Kester (1975)

Figure 15. T-budding

[42] The Grapevine

Layering Layering is a method of propagating own-rooted varieties that root poorly from cuttings. It is done by the development of adventitious roots on the stem while it is still attached to the parent plant. The technique is usually employed to replace missing vines, an alternative which can be used effectively. From own-rooted vines adjacent to a missing vine, a long vigorous dormant cane is bent down and buried into a trench of about 25 cm deep (Figure 16). The apex of the cane is left above ground leaving 2 - buds. New shoot growth on the portion of the canc between the ground and the parent \ine should be removed to enhance the growth of the new vine. After the new vine develops by itself with well-developed roots, it can then be cut off from the parent \inc. Generally, as a means of propagation, layering has limited application in modern viticulture.

Rapid Propagation Techniques The production of grapevine cuttings in open ground nursery is simple and economical. The rooting of cuttings can be speeded up by mist propagation of green woodcuttings or micro-propagation (Hartman and Kestcr, 1975). These methods permit the production of planting material within few months of obtaining die cuttings. Hcnce, several batches of these can be produced in one year. The techniques involved in these methods are too sophisticated to mention here. Green or soft wood cutting and micropropagtion methods are briefly outlined.

Green or Soft Woodcuttings These arc single nodded segment or green /soft woodcuttings obtained from the mother vines during the growing season. This method is practiced in glass house under automatically controlled intermittent misting with a fixed time cycle of on (ca 1 0 see.) and off (ca 90 sec) in combination with bottom heat to raise the temperature slightly

[43] Asfaw Zelleke above the ambient to enhance the development of root system (Hartman and Kestcr, 1975). The soft wood should be planted on well-drained rooting medium so that any accumulated exccss moisture could be removed. This is a rapid method of multiplying large number of plants from a mother vine in a single season. For example, it is possible to get about 300 cuttings from a vine that has 20 shoots of about 15-nodcs cach.

Micro-propagation

Definition Micro-propagation is the development of new plants from tissue (callus) or organ {seed, embryo, seed, shoot tips, root tips, etc.) grown in artificial medium under aseptic condition. The development of the new plants depends upon two major factors, namely: (a) the genetic potential of the cultured plants; (b) the chemical and physical environment to which the plant part is subjected. Micro propagation has been used in research laboratories throughout the world to isolate and grow plant tissues in aseptic culture sincc time immemorial. The method has been used extremely in tissue and organ eulture as a standard research tool in many physiology, pathology and gcnetics laboratories. Micropropagation has sev eral applications. The most important ones are the following:

• To establish disease free plants; • To isolate new plant variants; • To enable and enhance rapid multiplication of plant parts and maintain freedom from diseases; • To develop plants that arc difficult to propagate under normal reproduction; • To conserve germplasm; • To develop haploid plants; and • To rescue premature organs (embryos).

Place for micro propagation The place for performing micropropagation should be free of dust and other source of pollution. Well-sterilized room/place helps to remove contaminating organisms. Ultra violet (UV) light and germicidal lamps arc used to sterilize propagating rooms and w'orking place. This requires extra care to handle it. as it is harmful to the eyes or body. It is important to perform micro propagation in an enclosed, well-lighted and suitably ventilated place/room with very clean and dry atmospheric condition.

Required equipment/instruments Important equipment and facilities required for micropropagation arc autoclaves, laminar air flow' cabinet, refrigerators. pH meter, analytical balance, hot plate stirrer, Bunsen burners, water bath, racks, heat dry sterilization, washing area, distillation unit, shelves, florescent lamps, in some eases dark rooms, and several glassware.

[44] The Grapevine

Preparation of Media Plant tissues and/or organs are cultured in nutrient media that varies with the kind of plants and the purpose for producing the culture. Specific media have been developed empirically and now are in use for grape tissue (shoot-tip) culture. The media indicated below, which is a modified media of MS (Murashige and Skoog, 1962) is successfully used in Europe (Germany, Gebclrhoef) for grapevine micropropagation via shoot-tip culture. The required minerals, vitamins, sugars, growth regulators and others as adapted from the above laboratory arc presented in Tables 5 and 6 .

I able 5. Media composition for grapevine shoots tip culture

Media Amount Sucrose 20.00 g/l Gelatin 4 .00g/l Myo-inositole 0.10 g/l Na- EDTA 0.05 g/l Salt 1 100 ml/l Salt II 10 .00ml/l Salt III 1.00 ml/l Thiamin 1.00 ml/l Salt 1 (Macro a) Salt III (Micro a) A m ount k n o 3 38 g NaMo 0.125 g NH4N03 16 g Cu(No3)2 ,5h20 0.0125 g Ca(N03)2.4H20 9g CO(N)3)2. 6H20 0.0125 g MgS04 .7H20 8g Kl 0.50 g KH2PO4 5g Salt II (Micro b) M nS04 .H2O 2.0 g H3BO3 1-5 g ZnS04 0.5 g Weigh out media substances accurately and mix them thoroughly Source: From the Lab of Dr. Margit Harst Langenbudher

[45] Asfaw Zelleke

Table 6. Murashige and Skoog Revised Media Composition of Basal Medium

Organic Inorganic Salt (mg/1) substances (mg/l) NH4NO3 400.00 IAA 2.00 KCI 0.65 Kinetine 0.2 0 (or 0.04 for callus) KNO3 80.00 Thiamin HCI 0.10 KH2PO4 12.50 Nicotinic acid 0.50 Ca(N03)2.H20 144.00 Pyridoxine 0.50 MgSCU JH2O 72.00 Glycine 2.00 NaFe.EDTA 25.00 Myoinositol 100.00 H3BO3 1.60 Edamin 1000.00 MnSCU .4H20 6.50 Sucrose 20.000.00 ZnS04 .7 H2O 2.70 Difco Bacto Agar 10.000.00 Kl 0.75 Adjust pH = 5.7 - 5.8 in 1 N HCI/NaOH; EDTA = Ethylene diamine tetra acetate Source: Hartman and Kester (1975). In: Plant propagation. Aseptic Method of Micro-Propagation , pp: 509 - 528

I*rocedure for Culturing Organs and Tissues Shoot-tip culture is a wcll-dcvcloped and established micro-propagation of the grapevines. The book gives emphasis to this system following the procedure outlined by Hartman and Kestcr (1975). The other systems, because they require complicated procedures and facilities will not be discussed here.

3»hoot>tip culture implants preparation: This is a rapid method of asexually multiplying plants. The procedure involves excising the apical meristcm together with the top 1 or 2 leaf primordial to produce a small plantlct. The leaf primordial is important, as the mcristem itself is not able to grow independently

Surface sterilization: Keep the shoot tip under aseptic condition free of contaminating organisms. Continuously wash using tap water for at least 15 minutes and rinse at least three times using double distilled water in a sterilized container under the laminar flow hood. Use mild surfacc sterilants to disinfect the explants and finally rinse at least three times using double distilled water.

Inoculation into media: The small enclosing leaves at die tip are removed to expose the growing point. The tip of the next subtending leaf primordial is removed with sterilized scalpel and placed on the surface of a paper wick in a test tube with nutrient media.

C rowing condition: The shoot tip is allowed to grow in the test tube with adjusted photopcriod of 16 hours light and 8 hours dark using timer (automatic clock) and temperature around 25±2°C. The shoot-tip cuttings are placed in such a moderate light and temperature where adventitious root should develop in 2 to 3 weeks. Usually air conditioner and heater are used to regulate the temperature also providing uniform forced air ventilation. Growth is kept until the in vitro plant is large enough to be transplanted into a container where it grows to a full size plant. The medium needed

[46] The Grapevine for shoot tip culture is usually simple. The basic nutrient requirements are presented in die preceding section under Culture Media. After the plantlets have grown enough to produce small leaves, it can be transplanted into the field.

Other micro propagation procedure This category includes pollen grain eulture and embryo culture. The readers arc referred to Nitsch and Nitsch (1969) and Ammirats and Steward (1971), which arc "eports of most senior works in the respective fields.

Vficro grafting Micro grafting can be used to produce grafted vines from planting material in limited supply. This is usually done where stock and scion materials have been freed from . irus and crown gall by tissue culture.

Factors Influencing Success of Grafting The important factors that influence grafting are discusscd based on critical importance of cach such as: environmental conditions, compatibility, root development and protection.

Environment Optimum conditions of temperature, moisture and aeration arc essential to enable the cambial layers of the stock and scion to produce callus. Temperatures of 24-30°C and relative humidity of 90-100 % arc optimal for the succcssful development of the graft union. It is difficult to obtain these conditions naturally and modifications of the environment are necessary. This seems to limit its wide adaptation in all grapevine- growing areas of developing countries. Climate controlled greenhouses coupled with bottom heating facilities could be gainfully exploited.

Compatibility Compatibility refers to the ability to form a sound union (Hartman and Kcstcr, 1975). Plants of the same species usually graft readily with each other. However, varieties of 'ids vinifera present problems when inter-grafted. Occasional reports of incompatible combinations are usually attributable to virus infection. To ensure succcssful healing, the scion and the stock must be compatible with each other.

[47] Asfaw Zelleke

Root development on rootstock It is often difficult to promote root development on rootstock cuttings than on own rooted Vitis vinifera cuttings (W inkler et al.. 1974). Soaking rootstock cuttings in water may enhance root development, which may be due to leaching of inhibitors. Growth regulators can also be used to promote root initiation. According to Weaver emong the various synthetic auxins that promote root formation, indolebutyric acid (IBA) is the most effective in grapevine (Weaver, 1976). It may be applied as a conccntrated quick dip (200 mg/1 IBA ) with the basal 2 cm of cuttings dipped for few seconds or a dilute aqueous soak (200 mg/1 of IBA), with the basal 4 cm of the cuttings soaked for 24 hours. The concentrated dip is often convenient even though either of them can be used.

Protecting the graft Placc a stake by the grafted vine soon after planting. Cover the graft immediately with a mound of moist fine soil. Care should be taken not to disturb until the unions are formed. Suckering should be started when the grafts have started to grow and scion shoot can be tied to the stake.

[48] The Grapevine Chapter IV

Establishing Vineyards

A vineyard is an orchard of grapes produced for various uses. The cultivation of ^^-grapc vines as a perennial plant from the outset should receivc due attention as any neglect in the initial stages would considerably offset vineyard efficiency and becomcs unbearably risky venture. Some of the most prominent aspccts that must be considered in the establishment of a vineyard arc discussed here.

Site Selection It is important to study the site carefully for the establishment of vineyards before making decision to plant, as any wrong decision made in planting cannot be corrcctcd easily later. Several general questions need to be answered before a vineyard is established. Some of the important ones are proper site selection, which must take into consideration suitable climate: fertile soil; access to irrigation; disease and insect pest problems, and economic prospects of the crop.

Climate 'lie cultivation of grapes is significantly influenced by climatc, mainly by temperature. In general, the vinifera grape is successfully cultivated in the warm temperate zones between 34" N and 49" S latitudes (Winkler el al., 1974). The growth and development of individual varieties in certain areas within a region is limited largely by temperature. A variety that docs well in warm area may not do so in cool areas. There are also considerable varietal differences within the specics. Some varieties do well at all climates, but there seems to be no best climate for all varieties. The grapevine requires long warm to hot dry growing season and cool dormant season with heat summation ranging from 1700 to 5000 as degrcc-days above 10°C (Winkler el al., 974). It withstands neither intense cold dormant season nor humid growing season. Humid growing season is favorable for diseases and pests build up to which the vines are susceptible. Likewise, low temperature during the growing season is detrimental to the young growing grapevines. Areas that are frequently subjcct to frost during the early and late growing season should be avoided. Temperature further affccts the composition of berries including the sugar: acid ratio and contents of tannins and phenolic compounds, which consequently affects the quality of the grapes. Temperatures also control the types or classes of grapes to be grown in an area. Generally, cold areas arc recommended for wines grapes and warmer areas for raisin and table grapes production. Warmer areas are conducive for fast color development table grapes) and drying grapes (raisins). It is therefore, essential to refer to weather data and decide whether the nature of climate prevailing in the region under consideration is suitable or not.

[49] Asfaw Zelleke

In Ethiopia, generally regions with sub-moist tepid to cool mid-highlands (1900 m of altitude) provide favorable growing condition to general viticulture. However, lack of distinct long cool period, as present in northern temperate zones of grape growing, with a pronounced vegetative cycle of growth and dormant period (rest) ensures continuous vine shoot growth throughout the year, provided water is available. This however, induces general physiological problems such as apical dominance, where just the apical/terminal buds push leading to inadequate and erratic bud break.

Soil The grapevines are adapted to a very wide range of soil types even though there is preference for soil types among varieties. In various parts of the world, grapes are grown commercially on almost all types of soils, thus highlighting the wide adaptability of the Vitis species. However, there arc certain types of soil, which should be avoided for successful viticulture. Among these arc heavy clays, very shallow, poorly drained soils and soils containing high content of alkali salts, boron and other Boxic substances such as aluminum. The nature of the sub soils is important for vineyard establishment, because they determine the productivity and water holding capacity of the soil and the rooting depth of the vines. In general, grapevines arc deep- rooted plants, which do best on deep fertile, well-drained soils. Clayey subsoil with dense texture or un-fractured layers (hard pans) is not suitable for grape growing, since they are impervious to water and roots. Ethiopia has a wide range of soil types due to the variability of the parent materials and diverse topography across the country can create conducive soil conditions for the grapevines.

Majority of the vinifera varieties tolerate rather high concentration of lime in the soil (50-70% calcium carbonate) when grown on their own roots (Winkler et al., 1974). However, the grapevines are sensitive to saline soils, which should be avoided. The clay portion of sodic soils is largely saturated with sodium ions. They also contain considerable quantities of water-soluble sodium salts such as sodium chloride, sodium sulphate and sometimes sodium carbonate. These salts are harmful to growth of grapevines and interfere with uptake of water and essential nutrients in required amounts. The vinifera grapevine has a deep-root system capablc of exploring the soil to about 4 meters deep. Deep and fertile soils are recommended for good grapevine growth and heavy crop. High soil fertility is not so important for it causes the development of an extensive root system, which would consequently delay ripening, cause coarsc texture and upset the composition of berries. Therefore, it appears that it is necessary to advice against ccrtain soil types than to recommend the many different good soils for successful production of grapevines. Best results with table and raisin grapes have been achieved on alluvial valley soils varying in texture from sands to loams. There are however instances where even poor soils such as heavy clay or even shallow, poorly drained alkali soils, or even soils with hard-pans at 1 - 2 meter depth can produce good table and raisin quality. This perhaps could only be achieved if the climate is so favorable relegating soil factor to secondary importance.

[50] The Grapevine

Water Information on the annual precipitation and/or source of water for irrigation should be considered in site selection. The young vine requires frequent irrigation during the dry season. Mature vines should be irrigated only during drought though supplemental irrigation is recommended at flowering and fruit setting time in order to reducc abscission of flowers and fruits. However, the water for irrigation must be checked for the level of toxic salts. Using water with high amount of soluble salts should be avoided, as it could be more hazardous than drought.

Pre-Planting Activities Proper site selection is a pre-requisite for the succcssful establishment of vineyards. Important activities before the acUial field planting include land preparation, planning and lay out including crop geometry. The time of planting should be decided as early as possible to make the necessary arrangements well ahead of time. The various aspects of pre-planting field activities arc discussed here.

Land Preparation Preparing the land for planting requires considerable attention. It should be prepared at least one year in advancc. The land should be made thoroughly free of weeds, stones and trees, and leveled or graded. Incorporating of organic manure helps to improve the soil structure and facilitates better penetration of water. Deep plowing is the most common way of preparing land for a new vineyard. For this operation, a special single moldboard plough and a heavy-duty tractor (app. 100 hp) are required. This approach definitely favors an optimal root development in all directions. Deep plowing can be combined with sub-soiling, if a hardpan occurs in the proposed new vineyard. Care must be taken not to replant old vineyards unless the option of a new site is limited. Under such situations, it is desirable that the entire old vineyard condition should be reviewed thoroughly even if only a part of it is to be replanted. The status of soil-borne problem (nematodes in particular) of old vineyards should be critically appraised especially if the soil is sandy.

Planning and Layout Planning should start immediately following land preparation. Plot size and arrangement are generally decided by the extent of area, the availability of planting materials and the degree of mechanization. Plots arc either rectangular (most common) or square in shape. Plots arc laid out using strings or ropes. Base lines arc established by laying out strings into two directions from a common center (benchmark) forming a 90° angle. The angle (right angle) is formed following Pythagoras theory (the sum of the square of the adjacent sides equals the square of the opposite side). Pegs or markers should be inserted at the proper spacc for the vines.

Row Orientation, Length and Blocks The alignment of rows has an effect on microclimate. However, the direction of the prevailing winds, the slope of the ground and solar radiation influence the orientation

[51] Asfaw Zelleke of rows. Rows paralleling the direction of prevailing winds have a uniform distribution of foliage albeit additional handwork may be needed to keep the vine open. The slope of the ground must also be considered in row orientation in order to facilitate proper drainage and irrigation systems. The path of the sun is the other factor to be considered in row orientation. Grapes develop better color when ripened in bright, diffused light but exposure to direct sun (afternoon) will make grapes liable to scald. An east-west direction for a raisin vineyard will allow the direct rays of the sun to strike the drying grapes that are spread on trays between the rows and vines in the vineyards throughout che day. Northeast to Southwest directions are recommended for early table grapes and if it has to be planted on a sloppy ground the same needs to be done along the contour lines. In general, it is advisable to run rows from North to South directions so that vines are better displayed to maximize light interception by receiving morning sun on one side and afternoon on the other. This effect is more apparent with narrow rows or alleys.

Row Length The length of rows is generally governed by the uniformity of the topography and soil type along the rows and by the machinery to be used. Long rows are desirable with a machine bccause less time is lost in turning at each end. There is also, a row length limit for the straining wires: a strain of 2 0 0 m is considered maximal, for such length a trellis anchor may not be necessary bccause wires may be tied at an intermediate trellis post where the next strain continued from the other side. Row length is also governed by the needs of irrigation efficiency. If the vineyard is to be furrow irrigated, short row length is desirable.

Blocks It is advisable to divide vineyards into units or blocks, often of one variety per block. This enables systematizing cultural operations. Mixing up of varieties within a block complicates vineyards having timing constraints; such as pruning, spraying and harvesting. The allocation of varieties to specific blocks however, requires a balance of properties of the varieties against features of each block such as soil fertility, slope and frost.

Crop Geometry Vine spacing varies a great deal with a density ranging between 500 and 5 0 0 0 vines per hectare throughout the viticulture world. The choice of spacing between plants within a row is influenced by the soil type, varieties, type of machinery and availability' of water and method of pruning. Availability of planting materials also dictate row and vine spacing, with constraints of planting materials wider spacing is practiced, while the opposite is true with abundant materials available. Varieties that require canc pruning and cordon training should be planted further apart than head trained vines. The vigor of shoots affects row spacing as well. The v igorous varieties with long iiternodcs should be spaccd wider than the less v igorous ones. Likewise, if water is a limiting factor in the vineyard, spacing between vines may be wider since the benefits of closer spacing cannot be exploited. However, if water is not limiting but v ine's vigor

[52] The Grapevine is low, then closer spacing within rows is justifiable. Mechanized farms require wider spacing (3.5m x 3.5m). A wide pathway (4 to 5 m) every 15-20 rows arc recommendable to haul materials to and from the vineyards including harvested fruits. It is important to recognize that cost of planting, trcllising, irrigation, training and miscellaneous expenditure are directly related to row length per hectare but not \incyard area. For example, a decrease in row spacing from 3 - 2.5 m may necessitate considerable increase in these values. Hence, all costs increase resulting from narrower row spacing must be justifiable and in the absence of such justification, there is every reason for having vine rows spaced widely. However, early yields, greater yield potential and better wine grape quality are some of the relevant justifications for closer spacing. The commonly adapted spacing in Ethiopia is 2 m between vines and 2.5 m between rows. Nonetheless, whatever the row space choscn, it is important to have rows of equal width. Table 7 illustrates the relationship between row and vine spacing on the planting density of vineyards.

Table 7. Number of vines per hectare at different vine and row spacing

Vine Row Spacing (m) Spacing (m) 2.00 2.5 3.0 3.5 4.0 0.75 6666 5333 4444 3809 3333 1.00 5000 4000 3333 2857 2500 1.50 3333 2167 2222 1905 1667 2.00 2500 2000 1667 1333 1111 2.50 2000 1666 1333 1143 1000 3.00 1666 1333 1111 952 833

1 Preparing Holes Holes should be prepared well before the planting time at least 2-3 months ahead and the pits are to be allowed to weather. Pits of size 0 .6 m in diameter x 0.6 m depth arc dug out. This enables the grower to purchase the exact number of rooted cuttings (rooting needed). They should be planted immediately after dugout in favorable weather, i.e., early in the morning or late in the afternoon; otherwise, they should be placed temporarily in the shade under cool conditions until ready to be planted. Early preparation of the holes, therefore, will eliminate the extra care required to handle the rooted cuttings. Furthermore, doing the two operations (that is preparing holes and planting) simultaneously will cause a delay in the operation.

'Planting and Time of Planting

Selection o£ planting materials The planting materials are either cuttings or rooted cuttings. Cuttings arc usually used to propagate the grapevine varieties. These are planted first in the nursery to develop rooted cuttings or directly planted in the field. However, planting rooted cuttings is preferred over planting cuttings even though there arc cases where vineyards have been successfully established directly from cuttings. They may even develop faster than ihose started with rooted cuttings may. The more likely outcome from such a practice

[53] Asfaw Zelleke is the percentage of failures with a consequent cost of replanting and a prolonged jncvenncss in the establishment. Nevertheless, there are two possible sourccs of rooted cuttings/rooting:

• Internal source: The growers can producc their own rooted cuttings from reliable and healthy cuttings, and • External source. The grower can obtain the materials from reputable commercial nurseries or other growers. In any case, growers should be extremely cautious in selecting rooted cuttings. Avoid cuttings if they appear abnormal in growth, color or si/e. Oncc rooted cuttings are selected for planting, they should be handled with care until planting. If planting is to be delayed, rooted cuttings should be placed in cool and moist condition. It is however, important to make plans ahead of time so that rooted cuttings will be planted in the vineyard immediately after they are lifted from the nursery.

Planting rooted cuttings Roots are often trimmed before planting to facilitate the planting operation, i.e., transport, storage and planting of rooted cuttings. It is important to retain enough roots to establish good spreading and spacing of the main roots that are the basis for the vine's structural root system. Plants should be set in holes filled with, preferably wetted topsoil. In some areas of the tropics in particular, farmyard manure is added and mixed with the topsoil for filling. This procedure is not advisable from an ecological point of view. Under warm, wet conditions, most of the nitrogen fixed in the organic material will be released by nitrification and leachcd out before the plant is ready to use it. Application of organic material should take place later during the season when the plants start taking up nutrients from the soil.

At planting, first the tops of the rooted cuttings are cut back to a single spur of two buds. All of the roots except those at the base arc completely trimmed off. The basal roots are shortened to 8 to 10 cm. The rooted cuttings should be kept moist and damp during trimming by covering and occasional sprinkling of water. Rooted cuttings must be placcd in the center of the hole with proper alignment. Loosc-finc soil must be used to fill over halfway of the hole followed by relatively coarsc materials to the ground level and simultaneously trampling around the vine by foot to compact the soil. Such practice will enable the vines to stand firmly until growth commences. Vines on their own roots should be planted deep in order to keep them safe from damage during cultivation and to keep them wet between irrigation. Vines that are grafted should be planted deep enough to keep the graft union well above the soil level in order to avoid root formation from the scion wood.

Under Ethiopian conditions, rooted cuttings should be planted as soon as possible since the high temperatures favor the use of stored reserves and will decrease the vitality of the plant. Generally, planting should commence in June, as the developing plant needs a constant supply of water, which could be obtained from rainfall. However, if water supply is sufficient and growth of rooted cuttings/rooting in the nursery bed is satisfactory, planting in the field may be carricd out earlier in the dry season with

[54] The Grapevine supplemental irrigation. Late planting of rooted cuttings should be avoided as much as possible. It may however, be difficult to remove rooted cuttings/rooting intact from the nursery bed in the dry season without causing injury to roots.

[55] Asfaw Zelleke Chapter V

Husbandry of Grapevines

'T 'his chapter describes die most important aspects of viticulture practices that should be undertaken following vineyard establishment. It is important to protect the young vines from drying out in the field from the time it is lifted from the nursery until it is put in the planting hole in the field and immediately watered. Desiccation is often the most likely cause of failure of a newly planted vine. It usually takes 3-4 years for the grapevine to produce fruits if it is properly managed. The Debre Zeit Research Center through its collaborative research program had managed to get the first harvest in 2 years at Dire Dawa and Koka. The major aspects of grapevine management include cultivation, pruning, training, fertilization, thinning and harvesting at the proper time.

Managing Vineyards

Cultivation This is a common vineyard practice, and it is done by hand using hoes or mechanical means around and between vines as the spacing permit. The purposes of cultivation are many but only few are mentioned here. These are: to control weed growth; to facilitate irrigation and harvesting, to incorporate covcr crops, fertilizers, and manures into the soil to enhancc and promote the absorption and percolation of water by soil. The time of cultivation is usually decided by the purpose that it is designed to accomplish. Cultivation must be done as often as needed to control the growth of weeds. However, he time, frequency and depth of cultivation depend on the type of the soil, availability of labor, and type of implements used. In general, dry cultivation avoids soil pudding or packing. The young vines need special attention. They are susceptible to weed competition during the first growing season. Weeds retard vine growth by competing or water and nutrients or by smothering the vine foliage. It is important to apply recommended pre-emergence herbicides, based on types of weeds, during the first two seasons. Where herbicides are not used early and frequent tillage should be done to control the weeds.

[56] The Grapevine

Irrigation Young vines require frequent irrigation and this requirement increases as the root system develops and enlarges. Young vines have a lower capacity to tolerate hot dry „ spells; hence, they should be watered as frequently as possible. Weekly watering is desirable during hot dry periods. Availability of water dictates the method of irrigation. The amount of irrigation required varies between seasons, the cultivars and the soil. Different soils require different lev els and frequency of irrigation, hencc the quantity of watering must be determined for each soil type. Light sandy soils need less water more frequently than heavier clay soils. As a rule, vines should not suffer from a shortage of soil moisture, though the fruit produced from non-irrigated vines can have outstanding flavor and keeping quality and mature earlier than irrigated vines of the same cultivars (Winkler el al.. 1974). Generally, until near the beginning of fruit ripening, the soil of the entire root-zone should be re-wet completely. In years of drought, non-irrigated vines may producc wilted bunches with soft immature poorly sized berries (Vaadia and Kasimatis, 1961). Irrigation should therefore be regulated in order to keep the growth rate of berries moderate and uninterrupted. Excessive irrigation is likely to give large watery berries (Hale, 1959). Such fruits arc difficult to handle and usually bring poor prices. In low rainfall areas, irrigation should be reduced before harvest but with care so that water stress docs not develop especially if harvesting is prolonged. There are three main types of irrigation. These arc furrow irrigation, sprinkler irrigation and drip irrigation. Furrow irrigation could be the cheapest if the vineyard is not located on steep slopes. Sprinkler irrigation is easier though it may cause softening and splitting of ripening berries, as well as increasing the risk of fungal diseases. Initial cost of installing sprinkler system limits its wider use. In areas where water is scarce, drip irrigation is more practical and economical. Furrow and basin irrigation systems are more widely used in vineyards of Ethiopia.

Fertilization The application of fertilizer to vineyards is based on soil analysis and/or deficiency symptom manifested by the vines for specific mineral nutrients. The grapevine is unique in its requirement for fertilization compared with other horticultural crops. It can adopt itself to a wide range of soil fertility if other factors such as soil depth and moisture status are favorable. The grapevine has a root system that explores the top 3-5 meters of the soil profile. Hence, decayed and decomposed refuse arc good sources of nourishment.

Fertilizer application Fertilizer application is an important factor that affects the effective use of nutrients to mprove the productivity of vines. The time and amount of fertilizer application depend on the need of the vines, form of fertilizer, and the use of cover crops. Cost of fertilizer and intensity of rainfall determine the form of fertilizer to apply. Urea or ammonium nitrate is better forms of N in heavy rainfall areas and other nitrate forms can be used for areas with light rainfall. The amount of fertilizer applied can affect the growth of the vine and the development of the berry. Only judicious application of fertilizer will improve the quantity and quality of crops. It is, therefore important to

[57] Asfaw Zelleke consider the condition of the soil (soil fertility and soil structure) while planning a fertilizer program. Most of the vineyards in the country arc following a simple blanket recommendation based on the only two types of fertilizers. Urea and di-ammonium phosphate (DAP), which arc available in the country. The rate of fertilizers being applied in the different vineyards is in the range of 10 0 - 2 0 0 g per vine each of these ' fertilizers. These rates are not based on soil and/or plant tissue analysis. High level of mineral nutrition is basic for good growth of vines during the establishment years. Fertilization of young vines differs from the one used for mature vines. In young vines emphasis should be given to nitrogen supply, because high vigor resulting from high nitrogen is an advantage to the young growing vines, the limited root system requires more localized supply of nutrients. A young vine benefits from about 20 kg N/ha split into two small applications of urea (10 g or one teaspoonful per vine). For small plantings, urea or, ammonium sulphate or ammonium nitrate may be spread by hand along the row lines. It is an accepted practice to distribute a band of P into the planting furrow before planting. This method however requires care that the fertilizer must be placed deep enough to avoid burning by contact with young roots. Heavy (200 - 400 kg/hectare or 10 0 - 2 0 0 g/vine) application of super phosphate is frequently applied in this way. This method is not suitable to N application as it is mobile and can leach easily if placcd deep in the hole. The requirements for the different macro-and- micronutrients are covered in Chapter VI.

Protection from environmental hazards Winds are serious problem in some areas. Loss of leaves caused by the wind seriously affects the formation of the trunk framework It is advisable to establish windbreak in areas of serious wind problem. Planting cov er crops have the advantage of adding organic matter to soil following their incorporation besides reducing weed pressure.

Managing young vines The development of young vines follows a rather definite procedure. The procedure must be followed properly at the right time to direct the growth and to maintain the vine in the desired position. Usually three to four years arc required to complete the training in the highland areas where single crop is common.

Support Young vines require a temporary or permanent support. The type and the length of the support depend upon the type of the training system to be adopted. In some areas, supports are placcd at the time of planting. However, the time for placing the support is usually determined by the nature of the material to be used for support; the type of soil; problem of termites and the labor cost. Likewise, the kind of support is determined by economical factors, the objective of the operation and the system of training. Juniper is the best choice for a permanent support while treated eucalyptus is good enough for temporary' support. The training of young vines needs close follow up by a trained and /or experienced person. During this time all laterals have to be removed, leaving one vigorous shoot trained straight upward along the support or stake.

[58] The Grapevine

Training and Trellising Attaching the vine and its growth to the various forms of support is referred to as training. The main purpose of training is to produce and maintain vines of desirable shape that facilitates cultural practiccs (cultivation, spraying and dusting, paining, and harvesting), and capable of producing high quality fruit. Proper training facilitates pruning and most importantly, it provides good leaf exposure. Trellising is the art of forming the structure that supports the framework. Various trellising systems are adapted in commercial grapes production in different parts of the world. The trellis design used on a particular site must be related to the variety, spacing and vigor. The main functions of trellis arc briefly mentioned here.

• Facilitating even distribution of foliage to permit adequate light interception to buds and thereby improving bud fruitfulness; ventilation to control pests and disease and protect fmits from sunburn. • Improving condition for pollination, fruit set and pigment development in the skin of colored (red and black) varieties, and • Allowing the bunch to hang free of foliage, canes or cordons and provides convenience for handwork and harvesting.

In Ethiopia, the trellis is simple consisting of low, single wire cordon with 3-4 added foliage wires for canopy support. The other types of training systems should be considered based on future research to identify- the ones that provide efficient growth of vines under the prevailing conditions.

Pruning Pruning is the removal of canes, shoots, leaves and other vegetative parts of the vine.

Purpose of pruning Vines arc pruned to establish and maintain desirable form and shape; and to distribute the proper amount of wood over the vine. Properly pruned and maintained vines encourage productivity and facilitate cultural practices such as cultivation, irrigation, thinning, diseases and pest control, and harvesting. Judiciously distributed fruiting woods increase the production of high quality fruit over the years, and eliminate the cost of thinning in the regulation of crop production. Pruning rcduccs total growth and affects shoot to root ratio and fruit bearing capacity of vines. Proper pruning concentrates the activities of the vine into the parts left and hencc affect its performance for production of quality' crops.

When to prune In the temperate zone pruning is done when vines are dormant. Under normal conditions pruning during the dormant stage has little or no effect on the growth or production for the current season. Pruning in the tropics and/or subtropics where such natural phenomenon as dormancy is not explicitly clear, it is done several weeks after harvest. In Ethiopia, for example pruning, in the highlands (rain fed areas), is done in inid-to-latc August just before the end of the heavy rain. In the lowland areas where

[591 Asfaw Zelleke supplemental irrigation and harvest of two crops per year is possible, such as Merti Jjeju (Upper Awash Agro-Industry Enterprise) and Zewai (Horticultural Development Enterprise) first pruning is done in January and the second in July with a rest period of approximately 45 days after harvest. The major activities during the first four years in the highlands arc briefly discusscd as follows.

]?lrst year During the first year, the primary concern is to develop a good root system. Cultivation and irrigation should be facilitated as frequently as needed. No pruning is needed during the first year. By the end of the first growing season, the vine will establish its root system and develop a well-matured top growth. All canes except one strong cane must be retained during the pruning time. The reserved cane should be shortened to two or three well-formed buds. The vines should be staked or trelliscd at this time.

Second year In the second year, a single, strong well-matured cane is developed to form the permanent trunk of the vine. A strong shoot that is best positioned for growing vertically is reserved and all other shoots should be removed from the old wood. As the shoot grows, it should be tied loosely to a stake in order to keep it straight and vertical. The vines are either spur or cane pruned and head or cordon trained. In the case of the former training system, the vines to be head trained (spur or canc pruned) should have developed a strong canc to form the permanent trunk, and several laterals. The trunk should be cut off at the node abov e the level where the required head is desired (65-90 cm). All laterals on the trunk need to be removed. One to three laterals (depending on the size of the vine) may be cut back to one or two buds to function as fruiting spurs. For vigorous cultivars fruit cane may be left on cane- pruned vines. In case, the trunk-cane is small (less than 10 mm thick at the desired height of the head) it should be cut back to two buds just like the first year's pruning. In cordon training, a strong canc should be selected and pruned at 65-90 cm to form the head of the vine. The cordon system can be unilateral, bilateral and/or vertical. At pruning time, one lateral is selected to form a unilateral horizontal cordon; or two laterals to form the bilateral system. The remaining laterals below the point of branching or bending need to be removed. In the bilateral system, the two laterals div ide at about 10-15 cm below' the wire of the trellis that will support the cordon. The laterals should be tied loosely to the wire and then pinched after they hav e grown beyond the half waypoint to the next vine (bilateral) and close to the next vine (unilateral). If however, the canes arc not large enough to reach at least 30 cm along the wire beyond the bend, they should be cat back to within one or two buds spur. In vertical cordon, unlike horizontal cordon, laterals are allowed to dev elop along the main stem (trunk) which will be pruned to 2-3 bud spurs.

[60] The Grapevine

Third year In general, vines at this stage of growth bear crops, depending on their size. However, the main concern during the third-year is the development of the permanent branches. Therefore, on head-trained spur-pruned vines, shoots starting on the upper half of the vine are allowed to grow. Enough cancs should be reserved and cut back to spurs in order to facilitate fruiting. Usually 3-6 spurs (each with 2-4 buds long) are left according to the vigor and growth of the vine. Shoots that develop on the lower half of the trunk should be removed. On head-trained cane-pruned vines, one to two fruit cancs (8-12 nodes) should be reserved and tied to the trellis. At the same time, renewal spurs (2-4) should be left to provide canes for the following year. For cordon-traincd vines, shoots on the upper side of the arms should be wrcll-spaccd ( 1 0 -2 0 cm). Shoots on the trunk and on the underside of the branches should be rubbed off. Fast growing shoots must be pinchcd off to maintain a balanced and uniform growth. Pinching shoots at early stage will check growth and allow the weaker shoots to catch up. Shoots must be tied to the wire (upper) as soon as they attain full length in order to cistribute the weight of the shoots and the fruits along the trellis. At pruning time, spurs with 1 to 3 buds long should be retained at 15-30 cm. intervals along the upper side of the arms. The size and vigor of the vine generally decidc the number of shoots per vine. It is a common practicc to leave only one to two shoots per arm to grow as fruiting shoots in the 4th year. The vine/shoot must be retied to make the horizontal arms as straight as possible. Vertical-cordon is formed almost the same way as head- trained spur-pruned vine. The main difference is the pattern of distribution of spurs. In vertical cordon, spurs or short arms (4-6) are developed along the main trunk to form vertical cordon. Usually one shoot per spur/arm is allowed to grow and then pruned to short spurs (2-3 buds). The number of spurs to be reserved depends on the size of the vine and the total number of arms per vine.

Fourth year During the fourth and subsequent years, the primary aim is to stabilize the structure of the vine so that the essential operations are directed towards production of maximum yield of high quality. Vines must develop to the desired shape and form. Thus, head- trained vines should be developed into symmetrical form along the plane of the trellis, and the arm(s) of cordon-trained vines should be uniformly spaccd over the horizontal portions of the branches. During the subsequent growing seasons, water sprouts arc to be removed from the trunk of head-trained vines from the arms (branches) and trunk of cordon trained vines except those needed for developing new arms. This is a program pursued under most vineyard conditions in Ethiopia. There arc ccrtainly some variations between v ines growing at warmer areas. Under such situations, adjustments need to be made within the first two years.

[61] Asfaw Zelleke

Types of Training/Pruning

Head'training'Spur pruning In this system, the head of a vertical trunk is established at about 65 cm from the ground. Canes are pruned to spurs to produce shoots that would bear the next year crop (Figure 17). This method is mainly used on different wine grape varieties. This method is simple to train, inexpensive and does not require permanent support. The disadvantages of this method arc depressing growth, causing bunch rot and poor color development because foliages cover berries.

Figure 17. Head-training - Spur pruning

Head-training-cane pruning In this system, the form of the vine is similar in form to head-trained-spur pruned vines. Well-positioned normal canes, usually 2 to 4 per vine arc left at pruning time. The cancs are bilaterally trained on each side of the head or unilaterally on one side of the trellis (Figure 18). At pruning time, old fruit canes arc removed and fruit canes with 8 to 15 nodes long arc retained (depending on varieties) for fruit production. Cancs for the following year are produced from 3 to 4 renewal spurs (2-buds long) retained in the head of the vine. Cane pruning enables well distribution of fruits along the cane; allows full crop retention for small-clustered varieties and for varieties that have un-fruitful basal buds. The disadvantages include tendency of over cropping » fruit, high cost of pruning and training of cancs, and requirement for trellis.

[62] The Grapevine

Cordon - Training - Spur Pruning In this system, the vine lacks definite head. Instead the trunk is elongated vertically (least common) or horizontally (most common). The trunk usually rises vertically to about 65 cm from the ground. A unilateral or bilateral horizontal cordon extending in opposite direction along the wire is formed within about 25 cm of the adjaccnt vines. In training the cordons, the bend must be smooth and regular branches must be straight in order to avoid spurs/shoots at the bend, which might shade the rest of the spurs/shoots. The fruiting units (spurs) arc loeated at regular intervals on the upper surface of the horizontal branches/arms (Figure 19).

Figure 19. Cordon-training -spur pruning

, The cordon system has advantages and disadvantages. The advantages include well distribution of fruits; it allows fruits to hang freely at about the same level from the ground; fruits arc well exposed. The disadvantages are: it requires skill, trellis and permanent support; it is laborious and expensive. Cordon training is best adapted to table grapes and large clustered wine grapes.

[63] Asfaw Zelleke

Overhead Arbor or Te£lon -training The arbor is a structure on which the vines are trained overhead on a crosspiece supported at both ends. It is wide-topped and requires more wires. The use of this system is limited due principally to their high cost of installation and maintenance, albeit some countries arc still using this system. It may also favor the development of fungus disease and interfere seriously with spray operations. Both spur and canc- pruning systems are suited to arbor training. Young vines are allowed to grow till they attained the height of the arbor i.e. about 2 m, and then the tips arc pinched off to facilitate the production of side shoots in the region elose to the wires. Two vigorous shoots close to the cut ends are allowed to grow in opposite directions for training as primary arms. When these shoots attained the desired length, their tips arc pinched off on each primary arm with three laterals kept on either side at a distance of 60 cm along wires for training as secondary arms. The tertiary shoots, which develop, from the secondary arms will form the fruiting cancs (Figure 20).

Figure 20. Overhead arbor training

Other trellis systems, which are in use in developed countries are not included in this book. Their adaptability and economic benefits need to be critically assessed before recommending for their immediate use under Ethiopian condition and this awaits further research findings and recommendations.

Canopy Microclimate and Canopy Management Canopy management is relatively a recent development in commercial viticulture practices. It was during early 1980s the particular contribution of canopy microclimate to vineyard productivity, fruit quality and disease incidcnce has been elucidated tnrough systematic research. The information in this section was gathered from VEN 16 (Viticulture and Enology) in a winter quarter course that I attended in 1993 at the

[64] The Grapevine

University of California, Davis. The canopy of grapevine is a leaf and shoots system that includes stem, arm, cane, shoot and clusters of the vines. Thus, the length/size, number and orientation (growth) of these components determine canopy architecture of the vine. Smart (1988) describes the arrangement of the foliage condition of the canopy as follows.

• Continuous - foliage of adjacent vines intermingles and gaps are lacking « Discontinuous - canopies arc separated from vine to vine ® Divided - canopies of adjacent vines are separated into discrete foliage walls of the canopy « Crowded - large leaf area within the volume bound by the canopy surface. These are associated with high values of shoot density and ratio of leaf area per canopy surface area or leaf number.

According to Smart, an ideal grapevine canopy should:

« have provision to develop adequate number of fruiting canes, ® have provision for adequate leaf area for the fruits borne on it. ® avoid crowding of shoots and mutual shading of leaves, and o avoid exposure of clusters 10 direct sunlight.

Canopy Microclimate Currently, there is worldwide interest in using various canopy management practiccs to improve vine microclimate, crop yield, and composition of grapes and wines. Canopy microclimate differs from canopy ambient climate mainly due to the size, shape, arrangement and density of leaves within the canopy (Kliewer, 1988). Photosynthetic photon flux rate (PPFR), red: far-red (660:730 nm) ratio, wind speed, and evaporation rates arc the climatic factors most influenced by grapevine canopics, whereas air temperature and humidity are much less attenuated. Grapevine canopy microclimate largely depends on the amount and distribution or leaf area in a given volume and its relationship with aboveground climate. Amount of leaf area, in a given volume, depends on shoot density and shoot vigor. Kliewer (1982) refers to shoot density as the number of shoots per meter of canopy length and, therefore, is a measure of shoot crowding. Canopy density is defined as the amount of leaf area within a given volume. Accordingly, the indiccs of canopy density can be developed as:

• leaf layer number (LLN) or the number of leaves contacted by a fine rod passing through a canopy cross-section in the bud renewal or fruiting area (Smart and Smith 1988); • leaf area to canopy surface area ratio (LA/SA) as weight of cane pinning per unit canopy length (Smart 1982): and • leaf area index for horizontal canopics (Wilson, 1959).

Shoot vigor is usually dcscribcd in terms of rate of growth (e.g., cm per day). However, length and weight per shoot, leaf area per shoot and total shoot leaf area per unit length of shoot are all indicators of shoot vigor. The latter parameter has been

[65] Asfaw Zelleke termed "gamma” and indicates the lcafmess of shoots. Table 8 lists values of the above indices that arc found to be optimal in several wine cultivars. The training system usually, determines the canopy microclimate, which in turn influences physiological functions (photosynthesis, transpiration, photo-morphogenesis, respiration, Tanslocation, etc.), which ultimately determine crop yield, fruit composition, and fruit quality. Soil, climate and cultural practices can also influence vine physiological processes, yield and quality of grapes and their products. Of the cultural practiccs, the trellis-training system is singled out for emphasis since improvement in canopy microclimate, fruit composition, and crop yield by this means arc readily achievable, n addition to trellis training systems, canopy microclimate can be manipulated by two other methods (Smart 1985b). These are:

• Controlling shoot number and spacing, i.e. distance between shoots, and by control of shoot vigor, especially the total number and size of primary and lateral leaves per shoot. Shoot number can be controlled to a limited extent by pruning method and level. Generally, the greater, the number of buds retained at pruning, the lower is the percentage bud break. However, this varies with the variety, vigor and degree of exposure of shoots to solar radiation.

• Disbudding and shoot removal can also be used to control shoot number and reduce shoot crowding. However, this operation is labor intensive and usually results in loss of some crop yield. Available supplies of soil water and nutrients influence primarily shoot vigor. In deep fertile soil, with high water holding capacity; or where rain occurs throughout fmit development and ripening period, the means of controlling vigor are limited. Hence, site selection and choice of cultivars rootstocks arc important as well as using cultural practices that reducc levels of water and nutrients in the soil, such as year round cover cropping.

Canopy microclimate within the fruiting region could also be improved by removing leaves adjacent and opposite the cluster between fruit set and verasion. Removal of leaves in the fruiting zone has become widely adopted in most recent years in vineyards with dense canopies in California and in New Zealand, and is a long established practice in Europe (Kliewer el al. 1988a).

Canopy Management Canopy management or foliage manipulation consists of such operations that improves f'uit coloration and quality, vine productivity, fruit and wine composition, and facilitates vine protection sprays against fungal disease in grapes. Major emphasis of canopy management is usually to reduce excessive canopy shading and increase air circulation in the fruiting region. Canopy management practices commonly adopted to accomplish trellis-training systems, pruning level and method, shoot positioning and direction, shoot removal, leaf removal in the fruiting zone, and shoot trimming (Kliewre and Smart 1989). Leaf area available on a bearing shoot during the fruiting season has a remarkable influence on the development of bunch, berry size and dry matter accumulation in the berries. Reduction in the available leaf area will reduce the bunch size, berry size, its crispness and total soluble solids (TSS) content (Smart

[66] The Grapevine

1985a). Leaf removal is the most common practice adopted. Leaf removal is practiccd in colored varieties, which require light for proper color development. Two to three mature leav es and/or whole laterals should be removed from shaded side of the vine from the vicinity of bunches at verasion (Kliewer, 1982). Care should be taken to avoid cxccssivc leaf removal as it may hinder fruit ripening and encouragc sunburn. Leaf removal may also facilitate harvesting by removing the leaves to make the fruits visible. Removal of interior leaves may be useful for preventing bunch-rot incidcncc especially in late varieties following rain. In general, leaf removal increases sunlight fuxcs, allows air to penetrate the grapevine canopy and speeds up moisture evaporation from the berry surface. Smart (1987b) indicated that sunlight fluxes have three important influences on grapevine physiology. These are:

• The supply of energy for photosynthesis i.e. radiation in the wave band 400 to 700 nm, termed photosynthetic photon flux rate (PPFR); • Tissue heating cffccts, i.e. radiation in 300 to 1500 nm range, and • Photo-morphogencsis or pliytochromc effects, i.e. ratio of red to far-red radiation (R:FR or 660:730 nm).

Shading has been identified as a major factor in reducing grapevine yield and fruit quality and the effects of canopy manipulation on PPFR and R:FR ratios arc emphasized here. The effccts of PPFR and R:FR on photosynthesis of grapevines and nflucnce of canopy density and shading on photosynthesis have been extensively studied (Kriedman, 1968 and 1977; Smart, 1974). Smart et al. (1982) showed that there is elose correspondence between levels of PPFR and R.FR ratios within grapevine canopies. Furthermore, phytochrome also regulates the activity of key enzymes affecting fruit ripening, so that R:FR microclimatc could influence fruit quality. Grape leaves absorb about 95 % of red but only 2 0 % of far red light so that in dense canopics, the R:FR ratio may be less than 10 % of ambient conditions (Smart, 1987b). In grapevines however, there has not yet been a clear demonstration that phytochrome plays a key role in fruit coloration, ripening or in fruit bud differentiation.

Several studies on grapevines (Kliewer and Lider, 1968; Smart, 1982; Raynolds and Wardle, 1988) have compared the composition of shaded fruit with w'cll-cxposcd fruit. heir results indicate that exposed fruits are generally higher in sugar, total phenol, anthocianin, arginine and free and bound monotcrpenes and lower in pH, malate, potassium and titratablc acidity. Generally, all these are considered desirable particularly for high wine quality. In addition, experienced taste panels have generally scored wrincs made from highly shaded fruits lower than wines made from exposed fruits with respect to fruit charactcr disccmed on the nose and palate (Smart, 1988). Other management tools that can help to control shoot vigor and rcducc canopy shading includes wider vine spacing within and between rows, row direction, less vigorous rootstock, reduction in water status of soil and fertility and growth retardant.

[67] Asfaw Zelleke

Table 8. Grapevine growth and yield indices* for optimal wine grape canopy management

Description Ideal Undesirable Total leaf area/surface area per vine <1.2 >3 Leaf layer number 0 .7 -1 ,5 >3 Shoot spacing number of shoots/m canopy length 1 0 -1 5 >20 Fruiting weight (kg/m cordon length) <0.5 >1.0 Crop yield/pruning weight ratio 4 - 9 3 or >10 Mean cane weight (g) 2 0 -4 0 >70 Source: After Smart and Smith (1988) ‘The indices are usually measured at/or near harvest or after leaf fall

Diseases and Insect Pest Control Table grapes, which arc consumed fresh, the appcarance of the fruit is very important. However, ccrtain diseases and pests do create serious problems for the growers, which need to be tackled by adopting appropriate plant protection packages. The most important diseases, insect pests and others are covered in some details in Chapter VII.

Post-harvest Vineyard Management Proper vineyard management after harvest is essential to maintain sustainable productivity of vineyards during the following crop season. Thus, vineyard management including cleaning and maintaining of equipment used in harvesting operation is unequivocal. Therefore, because of the corrosive action of acids in grape juicc and the damaging effcct of other compounds, especially sugar, harvesting equipment needs stripping, cleaning, oiling and painting after each season. Trellising may need attention to repair damaged old poles and prevent loss of /sagging wires. Attention to the vines themselves is simpler while the vines are actively growing. Damaged shoots are readily identifiable, arc easy and simple to pull out. Finally, an assessment of the degree of bud damage permits a compensating adjustment to the bud level for next season's pruning. A post-harvest irrigation will encourage the retention of leaves without inducing active growth. This may allow the vine to increase its potential productivity the following season by continuing active photosynthesis, thus enhancing flower clusters development and carbohydrate storage.

[68] The Grapevine Chapter VI

Mineral Nutrition o£ Grapevine

he grapevines are able to grow and produce crops satisfactorily under diverse environments. In Ethiopia even though the production of grapes has not been systematicallyT developed and commercialized, the prevalence of wide range of environments could support successful viticulture. Though the existing vineyards have not been studied, especially in terms of their nutrient requirements, it is unequivocal that the nutrient needs for the grapevines and the status of same in the soil be studied and established. Till then, the adoption of more intensive production tcchniqucs from developed countries including a judicious fertilizer program for optimizing production and productivity of the grapevines in the country deserves due attention albeit research results of one place/country may not necessarily become applicable elsewhere. During ihe last few decades, however, there has been an increased understanding of the nutritional needs of the vines in the developed countries where viticulture has advanced significantly.

n most developing countries, it was common to grow grapevines without using commercial fertilizers unless serious symptoms of nutrient deficiency on vegetative parts of the vine or reduced crop production are observed. In these countries including Ethiopia, the attention given to research on horticultural crops in general has been so nsignificant that no precise research recommendations arc available with regard to ypc. rate, method, and time of application of fertilizers to the grapevines in particular.

Vineyards usually respond to application of fertilizers; but the requirement of different nutrients varies considerably from placc to placc even within a given country. In the past, it was a common practice to apply manure in vineyards in Ethiopia, only if it is available. Sincc the inception of commercial vineyards in the late 1970s, there has been an increased understanding of the fertilizer needs of grapevines. This has been stimulated largely by the expansion of vineyards by the state owned enterprises.

Several studies have shown that over the vegetative period in most spccics, foliar concentrations of highly mobile nutrients (N, P and K) dccrcasc partly due to increasing dry weight of foliage while the less mobile elements (Ca, Mn or Fc) accumulate in the leaves. Thus the leaf blade is an ideal vine part for determining the nutritional status of vines. The time of sampling and index tissue to be sampled arc important questions to be addressed in a particular agro-ecology. In routine sampling, experience have shown that the bloom time sampling has proven to be the most important, taking only petiole at the eluster position and with follow up samples taken

[69] Asfaw Zelleke on vineyards in question at about a month after bloom. However, nutrient status of leaf plus petiole samples taken from opposite to the first cluster at the end of bloom and another one at the beginning of ripening and averaging of the two results can also be considered.

n many grapevine growing areas of the world, deficiencies of nutrient elements (P, K, N, Mg, Ca, B, Zn, Fe and Mn) have been widely rccognized in influencing growth, development, yield and quality (Kliewer and Cook, 1974). These elements play significant role as components of grapev ine and its physiology. Some are involved in trapping of energy; some form part of the enzyme systems acting as catalysts in chemical reactions in the cclls of the plant while some are part of the structural framework of the vines. The problem of sulfur, copper, molybdenum and chlorine has not been observed/reported in most vineyards in the world and in this book as well. If an element is not adequately available, the performance of the vines bccomes sub- optimal. If any of these elements is deficient, it can restrict growth of vines or affect the color and shape of leaves, manifesting varying deficiency symptoms (Winkler et a!., 1974). Therefore, two types of laboratory diagnosis methods are considered globally to provide sound recommendation of fertilizer type and rate for the grapevines. These arc: soil and plant tissue analyses. The application of soil and tissue analyses, the beginning of modern approach to determine nutrient requirement, is considered logical. Soil analysis has distinct advantage over tissue analysis. The nutrient supplying capacity of soil as well as site suitability could be determined before the establishment of a vineyard. However, the utility of soil analysis in predicting nutrient needs of perennial crops such as grapevines could be limited due to the discrepancies between the physiological and temporal complex systems of nutrient uptake process and procedures of extraction of nuu ients in the laboratory. On the other hand, tissue (leaf and/or petiole) analysis is much effective and reliable since the result represents the concentration of nutrients that the grapevine is able to remove from the soil (Cook and Kishaba, 1956). Nevertheless, soil analysis could be informative concerning possible toxicities of salts and knowledge of the pH, which can be useful in predicting nutrient problems especially for P, which is liable for fixation in the soil to unavailable forms such as aluminum phosphate at high pH and ferrous phosphate at low pH (Reiscnauer, 1976). Except these factors, the analysis of soil for nutrients appears to be of little practical value. Reisenauer showed that the rate of uptake and accumulation of nutrients are function of growth rate, which depends upon site, productivity, age and management indicating that calculation of biomass: nutrient content ratio (nutrient use efficiency) may give more valuable information than the absolute nutrient amounts in view of nutrient demand. Traditionally, the essential elements have been described as major (macronutrients) and minor (micronutrients) thus describing their quantities needed by plants. The macronutricnts (N, P, K, Mg, Ca and S) occur in large amounts (0 .2 to 3% dry weight) in plant tissue. The minor elements (Fe and Mn) are found in smaller amounts and these include iron and manganese (50-150 ppm dry weight) and boron, copper, zinc and molybdenum (0.5-40 ppm dry weight). The minor elements though arc needed in much smaller quantities, the deficiency could be as disastrous as that of a major element.

[70] The Grapevine

Table 9.The levels of mineral nutrients under different conditions in leaf tissue sample Nutrients Unit Concentration range Deficient Sufficient High Toxic Nitrogen: P/F = < 340 500-1200 >1200 —

N03-N mg/kg P/F = <0.15 0.22 -0 .53 <0.53 N03 % L/F= < 2.9 3 .9 -5 .0 >5.0 N % L/V 2.2-4.0 >4.0 Phosphorus % P/F = <0.15 0.2-0.46 >0.46 L/F = < 0.18 0.25 - .04 >0.40 L/V 0.15-0.3 >0.3 Potassium % P/F = <1.0 > 1.5 L/F = <0.8 1.0-1 L/V = < 0.6 0. 8 -1 .6 P/V = < 0.6 1.2 -3 .0 Magnesium % P/F = < 0.2 > 0.3 L/F = 0 .3 -0 .6 L/V = <0.2 0 .3 -0 .6 Ca. % P/F 1.2 - 2.5 L/V 1.8 - 3.2

Boron mg/kg P/F = < 25 3 0 -1 0 0 L/V = < 25 3 5 -1 0 0 Zinc mg/kg P/F = <0.15 >26 > 100 L/F = < 30 3 5 -6 0 > 300 L/V = < 19 3 0 -6 0 Mn mg/kg P/F = <20 >25 L/V 25 - 200 Cl % P/F > 1.0 L/V < 1.3 PA/ < 1.5 1 8 - 2.0 >zo Na % P/F >0.5 P/V 0.1 -0.4 0.5-0.6 >0.6 L/V < 0.1 >0.5

Source: Robinson and McCarthy 1985. Christensen et al. 1978; Cook 1966 and Cook and Kishaba 1956.

P/F = petiole at flowering PN - petiole at verasion: UP = laminae at flowering: UV =

laminae at verasion: - = information not available it is important to highlight the significance of each element with its impact on the growth and development of grapevines and understand the effects of their deficicncy. This section therefore aims to provide information to grapevine growers, on sound fertilizer program based on logical decisions and/or levels of nutrient elements present in the soil. In general, a fertilizer program should be so devised as to complement the ability of the soil to provide nutrient elements and to compensate for the crop removal so that they could grow and produce crops efficiently. Hence, the facts in this Chapter, which are gathered from prominent reviewed literatures (Cook, 1966; Cook and Kishaba, 1967; Cook, 1967; Winkler et al., 1974; Christensen et al., 1978; Finck, 1982; Robinson and McCarthy, 1984) can be used as potential reference for possible modification through effective survey work and research on local vineyards in the future.

[71] Asfaw Zelleke

The five major and some minor plant nutrient elements commonly found in fruits and canes at deficiency, normal and toxicity levels is presented in Table 9 (Cook and fCishaba, 1956; Cook, 1967 as modified by Robinson and McCarthy, 1985). It is the author’s strong conviction that the data in the tables can be used as a reliable nformation in studying the soil and tissue nutrient levels in the local vineyards.

The Macronutrients

Nitrogen (N ) Nitrogen fertilizers are chemicals that contam the nutrient element N in absorbable form, chiefly as ammonium and nitrate. Nitrogen is a primary component of proteins, chlorophyll, etc. and is essential part of the protoplasm. The protein components have both structural and catalytic functions. It is one of the most important nutrient elements in vineyards even though the amount needed per vine is not as high as that of other fruit crops. Nitrogen makes up 10,000 to 20,000 ppm (1-2%) of the dry matter of the grapevines (Flinck, 1982).

Sources Nitrogen reserve in the earth’s atmosphere is very high consisting of about 80% (Finck 1982). The quantities of N -fertilizer produced depend mainly on the energy' requirements. Finck showed that production of 1 kg N in the form of fertilizer requires about 40,000 KJ (kilo joule) which corresponds to the caloric value of 1 kg oil. Most of the native (original) N in the soil is derived from decomposition of vegetables and soil organisms. N from the air is also fixed by free-soil living microorganisms (Clostridium and Azotobactor) and by bactcria (Rhizobium)

Rainwater and water from deep wells also contain N as nitrate, which supply part of or all of the required nitrogen by plants. Most of the nitrogen compounds in the soil are converted to the nitrate form by certain organisms (Nitrosomonas and Nitrobactor).

Organic nitrogen is also derived from legume covcr crops, manures and grapc-pomace, which is crushed grapes after the juice is extracted . The nitrogen present in these materials vary considerably. The use of alfalfa, vetches, and beans etc. as cover crops or as part of crop rotation schcmes has been a common practicc prior to the era of inorganic commercial fertilizers. The bacteria (Rhizobium) on the nodules of the roots of leguminous plants fixes atmospheric nitrogen in the soil. These crops also improve soil tilth and facilitate water penetration. Likewise, steer and dairy manures contain nitrogen in appreciable amount. Poultry' manure however, contains almost twicc that of the former. The main problem with manure is the likely of its shortage to sustainably satisfy the amount needed per hectare.

Role Nitrogen is the primary component of protoplasm. It is an important component of amino acids, chlorophyll and others. Nitrogen deficiency reduccs growth and causes The Grapevine carbohydrate reserve accumulation in the vine. Accumulation of carbohydrate can be reversed due to excess vegetative growth under heavy nitrogen utilization (Finck, 1982). In the book, because of the diverse use of nitrogen in the plant system, attempt has been made to give to it a relatively wider coverage than the rest of the nutrient elements..

Uptake and Utilization The grapevine absorbs nitrogen from the soil as nitrate and transport it to the leaves where it is transformed into protein and other N compounds. During protein synthesis, tie nitrate is reduced to nitrite and then to ammonium. Nitrate reductase and Nitrite reductase arc involved in the two successive reducible reactions. The activities of these enzymes depend on temperature, light and available nitrate that low temperature, light and nitrate levels would lessen their activities . Ammonia is converted into glutamine and other amino acids and into grapevine proteins. During the dormant season arginine - which accounts about 50 to 90% of the soluble nitrogen in roots, canes and trunks is t:ie important form of stored N in the grapevine that the vines utilize this N from this source for its early growth (Kliewer, 1971).

Deficiency Symptoms The nitrogen level in the soil may be affected by low temperature leading to reduced chlorophyll synthesis and injury causcd by nematodes and phyloxcra. The grapevines unlike other crop plants do not readily show a need for nitrogen albeit of the major elements, nitrogen is the more likely to be deficient. It is when the deficiency is severe that the symptom is recognizcd (Christensen et al., 1978). They described the deficiency systems as follows: foliages turn pale green and then yellow; young shoots, petioles and cluster stems turn pink to red; reduced shoot growth; dead tissue occur between main veins of the lower leaves; leaf blade wilt and abscisc; low argeninc level in dormant cancs and juice. In general, the most obvious symptoms of nitrogen is reduced vigor that shoots and leaves become smaller. On the other hand, too much nitrogen may also have an adverse effect on the production of grapevine leading to an increase in vigor. High vigor/vegetative growth arc associated w'ith a reduction in fertility and fruit set (May and Antcliff, 1963). Excess nitrogen has also been implicated in bud and bunch stem necroses.

[73] Asfaw Zelleke

Application of Fertilizers Proper vine growth could be maintained through nitrogen fertilization based on experience, observation and verification with periodic tissue analysis. Vine growth is affected by the nitrogen level in the soil, soil type, inherent vigor of the variety and the root system. The type of soil affects the rate and frequency of fertilizer application. Sandy soils require more frequent and high nitrogen rate as compared to the heavy clay soils. Inherently vigorous varieties also require careful regulation of nitrogen fertilization while less vigorous varieties are inherently limited from nitrogen fertilization (Winkler et al., 1974).

Rates The rates for the different nutrient clement application arc presented in Table 10. These rates are based on many trials, survey and growers’ experiences in the USA (Christensen el al., 1978). The guideline is included in here to show the rates, soil types and age of vines so that they may be tried with sound survey works as precondition for subsequent modification and/or adjustment in order to make the guideline fit to the local prevailing conditions.

Table 10. Nitrogen application guidelines for mature and young vineyards

Suggested rates (actual N kg/ha) Soil and vine characteristics Matured vineyards 0 - 4 5 Deep, fine sandy loam, especially those planted to high-vigor grape varieties. Higher rates may be justified wherever heavier foliage is desirable. Fruit coloration may be delayed with excess N rates in colored table grape varieties Repeated applications of over 65 kg N annually can lead to excess N levels It may be desirable to stop N applications entirely for several years or more where high vine N levels are encountered. 5 5 -7 0 Sandy loam; vines of medium or normal vigor. 7 0 -1 0 0 Sandy and loamy sand: old or marginal vineyards where higher rates are used to maintain vine growth. Young vineyards (first and second growing season) 0 - 2 5 Sandy loam to loam with a crop history of N application, with crops that usually do not require N for at least several years. For questionable areas use 25 kg N per hectare. 30-35 Loamy sand soils 4 5 -6 0 Coarse, sandy soils. This rate should be split into two separate applications of 25 to 30 kg, preferably the first one early in the growing season and the second one at (early) fruit set. Source: Christensen et al. (1978)

[74] The Grapevine

Materials A number of common fertilizers as sources of nitrogen arc presented in Table 11. It is unequivocal that their long-term uses should be monitored periodically to avoid problems in the soils such as lower pH or acidic soils. Legumes and manures are good organic sources of nitrogen.

Timing ” he timing of application of nitrogen fertilizer depends on soil condition, vine growth and the type/form of nitrogen fertilizer and its availability. Nitrogen fertilizer is mostly needed during rapid period of shoot growth and berry development after bloom. The exact time of nitrogen fertilizer application depends on the form of nitrogen, irrigation schedule and soil texture. Nitrogen can be applied just before pruning regardless of the form available. In general, all forms of nitrogen fertilizer could be applied starting few weeks before or at pruning until bud break provided the soil conditions are favorable. o that effect, the different forms/types of common commercial sources of nitrogen fertilizers, the amount needed and the pros and cons arc shown in Tabic 1 1 (Winkler et al., 1974; Christensen et al., 1978; Finck, 1982; Robinson and McCarthy, 1984;). The common commercial sources of nitrogen fertilizer are:

Nitrate: It is immediately an effective fertilizer and is therefore especially suitable as “top fertilizer” (Finck, 1982). Nitrates are soluble in water and have the tendency to each excessively under heavy rainfall and when the monthly distribution is unpredictable. Nitrates should be applied before bud break preferably just before or at pruning time.

Ammonium: This form of fertilizer should be applied before bud break provided hat the soil is moist enough by rain or supplemental irrigation. Moisten soils allow fixation of ammonia on soil particles. Ammonia is then converted to nitrate form by microorganisms. Then, nitrogen in the form of nitrate is free to move downward to the oot zone with irrigation water. When ammonia fertilizers arc applied and left on dry soil surface, some ammonia is lost to the air due to volatilization. This however, depends on soil pH, soil texture and temperature. Sandy soils with pH over 7, show greater losses while sandy loam or loam soils lose much more less ammonia Christensen et al., 1978).

Urea: Urea has been used as sourcc of nitrogen fertilizer with excellent results cxccpt on soils with pH 5 or lower, it has not been satisfactory (Childers, 1966). Urea has to be converted to ammonical form and then to nitrate by bacteria before it can become available to the vines. A delay in irrigation will transform urea to ammonical form and become fixed on soil particles until it is converted to the nitrate form by bacteria (Winkler et al., 1974). According to Christensen et al. (1978) extra carc is required while applying N fertilizer in order to ensure maximum nutrient use efficiency through the best placement for maximum uptake by vines with minimum loss due to denitrification and/or leaching with irrigation water. If the fertilizer is to be applied after the rainy season, it should be applied in the furrow' area where irrigation water

[75] Asfaw Zelleke can move it down to the root system. In general, it is important to treat weaker or vigorous vine area in a vineyard to adjust to the most judicious rate; spot treat weaker vines or area with additional nitrogen at flowering.

Table 11. Commonly available commercial sources of nitrogen and the amount needed to supply the respective nitrogen rates per hectare

Amount needed to supply the following N rates ______per hectare______N carrier/amount Percent 23 kg 45 kg 68 kg Advantages/disadvantages Anhydrous ammonia 82 27 56 83 In irrigation water: fertilizer distribution as uniform as water distribution and penetration. Some surface losses into the air may occur. Ammonia solution 20 114 227 341 Has lower free ammonia does (33 gal) (66 gal) (99 gal) anhydrous. Ammonium sulfate 20 108 216 324 Acid residue suitable for alkaline soils, but undesirable in very acid soil. Requires rapid soil incorporation. Ammonium nitrate 35 69 138 207 High N percentage-half immediately available, half delayed Calcium nitrate 15 147 293 439 Immediately available. More expensive per kg of N than most other forms. Urea 45 49 114 148 High N percentage. Requires immediate incorporation or irrigation to avoid surface loss of N into air Urea +ammonium 30 70 140 210 Have advantages of both urea and nitrate (UAN) (14 gal) (28 gal) (42 gal) ammonium nitrate. Must be placed solution below soil surface to avoid surface loss of N into air Source: After Christensen etal.(1978). + Non-acid former

Phosphorus (P) The deficiency of phosphorous in most vineyards of the world is rare (Christensen el al. 1978). In Ethiopia there are no documented P deficiency symptoms or responses in local vineyards albeit blanket application as diammonium-phosphatc (DAP) is common. In general, grapevine in common with most dcciduous plants has a rather low P requirement and/or a low enough utilization rate that the roots, active over a longer period than the annual crops, arc able to supply what is needed (Robinson and McCarthy, 1978).

Sources: P exists in soils primarily as calcium, iron, and aluminum phosphates and in organic forms (Christensen el al.. 1078). They indicated that most of the phosphorus is slightly soluble, but it gradually solubilizes and is absorbed by plants from the soil solution as ortho-phosphate (H2P 0 4).

Application: The primary requirement of P in most local vineyards in Ethiopia is net through diammonium phosphate (DAP) applications ranging from 50 to 100 g per

[76] The Grapevine

\ inc usually at pruning time. It is true that in the soil profile the mobility of P is low. Thus, the uptake of phosphate fertilizer depends on root growth and the root morphology of the vines (Winkler et al., 1974). It is however important to incorporate phosphate fertilizer into the soil. Phosphate fertilizer is applied either as a placement or as a broadcast. Placement of fertilizer is found to be superior to broadcast treatment as it ensures high concentration of the fertilizer to meet a more limited soil volume. Phosphate fertilizer can be applied at any time of the year provided the P fixation capacity of the soil is not too high. Under such situation, water-soluble phosphate materials should be applied preferably after bud break. In soils in which available P levels are adequate application of phosphate can be made every second year. It is also important to note that in most mineral soils mobility of phosphate is rather low so that P is scarcely leached into the deeper soil layers while in organic soils, movement of P fertilizer into deeper soil layers has been observed (Mengel and Kirkby, 1987).

Role and utilization: Robinson and McCarthy (1978) showed that P is readily mobilized and can be transferred from older tissues to actively growing ones. It involves in the energy transfer mechanism in the plant. Grapevine needs less phosphorus than that of other macronutricnts. Thus, crop removal of P is only a :raction of the other macronutrients, particularly potassium, or calcium. This low P equircment and the grapevines’ ability to extract adequate amounts of P from soil could explain in part, the absence of its deficiency in most vineyards (Winkler et al., 1974). In this regard, the discussion on the phosphorous and other nutrients is not as detailed as it is for the nitrogen. The application of P at the rate of 100 g/vine has been used in research trials at the Debre Zeit Research Center and its sub-centers albeit its availability is affectcd by soil pH.

Deficiency: The deficiency of phosphorus has not been reported as a common problem in most grape producing areas of the world. Deficiencies based on nutrient culture include: a reduction in shoot/root growth; leaves become small and dark green; leaf margins turn down without rolling; under severe deficicncy leaves develop red, punctiform spots. Phosphorus deficiency may be one component of the nutrient imbalance brought about by low soil pH. Excess phosphorus fertilization is more common in vineyards becausc of the immobile nature of the fertilizer. This has been observed in most of the vineyards in Ethiopia (personal observation). It should be noted that excess phosphorus might induce zinc and iron deficiencies (Christensen et al., 1978).

Potassium (K ) The potassium need of the grapevine arc relatively high and arc comparable to the demand for nitrogen. Potassium deficiency in Ethiopian soils is generally considered insignificant (Murphy, 1968). The reasons in part, could be attributed to the adequate reserve of K in most soils and its resistance to losses from leaching.

Sources: Most of the K in soils is derived from minerals, such as micas and feldspars (Christensen et al., 1978). These minerals are only slightly soluble and arc

[77] Asfaw Zelleke

usually found as large-sized particles. Under the influence of weathering factors. K is mineralized and is available to plants as positively charged ions, which become attached to clay colloids or to organic matter in the soil. Thus, the available K level in Lhe root zone at any given time appears to be a more important consideration than the :otal supply itself. The total K in minerals ranges from 0.15 % in sands to 4 % and higher in clay soils.

Application: K fertilizer is supplied to crops as a straight fertilizer or in the form of compounds. The most widely used and less expensive potash fertilizer is potassium chloride (KC1, 60% K20 or 50% K), which is known as muriate of potash Winkler et a i 1974). K fertilizers are usually applied as broadcasts; but band allocation is recommended only in soils with a low level of av ailable K or with a high K fixation. According to Winkler and his group, the extent of fixation is the greatest in clays and clay loams while smallest in sand soils. i&ole and utilization: The function of K in grapevines is not precisely established. Much more is known about the effects on vine growth and crop yields at [|mes of its deficiency. It is not found as part of organic compounds and constitute only 1-4 % of plant dry weight (Christensen et al., 1978). Vines need K for the synthesis of sugars and starches, proteins and for cell division in neutralizing organic acids, regulating the activity of other mineral nutrients in plants, activating certain enzymes, and has role in adjusting water relations. It increases the oil content of certain fruits, and contributes to cold hardiness. The demand for K increases during fruit set, when greater amounts accumulate in the ripening fruits (Winkler et al., 1974).

Deficiency: The responses to K. fertilization have been obtained only in vineyard areas with visible symptoms of deficiency. Its deficiency is more common in the less fertile sub-soil and sandier soils. The deficiency symptoms of K vary with the stage of development of leaf blades. Leaf symptoms are seen first on leaves in the middle portions of the shoots. Yellowing of leaf colour begins at the margin or outer edge of the leaf. In all varieties, marginal burning and curling cither upward or downward usually follows. Vines severely deficient in K tend to have fewer and smaller, tight clusters with unevenly coloured, small berries. K deficiency symptoms many times arc confused with those caused by moisture stress during hot weather prior to harvest. Moisture stress, however, causes a general leaf bum of an irregular pattern being most prominent on the older, basal leaves. Vineyards showing deficicncy symptoms should be marked during the growing season and this will pinpoint the vines to be treated during the dormant season (Christensen et al., 1978).

Materials: K is usually reported in the oxide (K:0) form, also called potash. Potassium fertilizer is commonly available in three forms each with different potassium content as reported by Christensen et al. (1978). The three forms are:

• Potassium chloride (KC1, muriate of potash)-52 % K (62 % K20) • Potassium sulfate (K2SOi, sulfate of potash>44 % K (53 % K:0) • Potassium nitrate (KNOO-37 % K (44 % K.-.0) plus 13% total nitrogen

[78] The Grapevine

Christensen and his co-workers reported that one fertilizer form offered has no advantage over another in terms of vine responses if equal amounts of actual K are used. Thus, indicating that the choice of K source will depend on relative cost and availability of the materials and on soil and vine conditions. They further indicated that potassium chloridc is the most economical source of K. However, it must be used with caution, as irs chloridc content might lead to salt injury of vines under some conditions. It is normally used during the dormant season and should be avoided during the growing season. The relatively high cost of potassium nitrate eliminates its use in vineyards as soil application. Potassium sulfate is slightly more expensive than potassium chloridc, and is safe to use during the dormant season. However, it should be used with some caution during the growing season, especially on young vines, because experience of its use on the grapevine is limited. Thus, from a practical point of view, the choicc of K narrows down to either potassium sulphate or potassium chloride if locally available.

Rates: The rate of K fertilizer application depends upon the fixing power of the soil. A high rate is desirable when the K fixing power of the soil is high. Quick response can be achieved by a single heavy application rather than in small amounts applied annually. In general, the degree of vine recovery and its effectiveness are affected by- higher rate.

Time, methods and frequency o£ application; Just before the onset of dormancy is a good time to treat plants with K. Otherwise, the fertilizer should be applied before the first irrigation in early growing season, before bud break. It is recommended to placc K fertilizer deep in the soil in band close to the vine. This places the fertilizer near the root zone to enhance soil fixation. The fertilizer could also be applied by hand in the furrow on each side of the row. The furrows should be left open to allow rainfall and irrigation water to move the fertilizer. Single application of K fertilizer at recommended rate can sustain adequate K tissue levels and eliminate leaf symptoms for about five years (Christensen et a/., 1978). Higher rates could last for longer years. It is however, advisable to observe the vineyards closely to monitor die tissue levels of K by collecting petiole samples for analysis. This approach will help in anticipating the appropriate time for a follow-up of K fertilizer treatment.

Magnesium (Mg) Magnesium is a component of the chlorophyll molecule. The deficiency of Mg is widespread in sandy soils of low cation exchange capacity, i.e., low silt, clay, or organic matter content and appears on some calcareous and slightly sodic soils (Christensen et al., 1978). Young grapevines are more susceptible to deficiencies because their root system does not penetrate the subsoil which is higher in Mg. Christensen and his coworkers indicated that the deficiency of Mg is more common in Grenachc, Thompson Seedless, Barbcra, Malbcc, and Gamay varieties. Winkler et al. (1974) reported many instances of magnesium deficiencies induced by heavy potassium fertilizer applications. Even though antagonism between Mg and K should

[79] Asfaw Zelleke be of concern, information on K induced Mg deficiencies in the local vineyards is not yet available.

Sources: Magnesium (Mg) is derived from parent materials such as dolomite, biotite etc. as a result of weathering. Plants absorb magnesium ion (Mg*^) from the cation exchange complex where it is attached to negatively charged clay particles and organic matter.

Application: Mg is applied as carbonate, oxide or as sulfate. Despite the cost, sulfate fertilizers are more rapidly effective than carbonatc fertilizers. Application of dolomitic limestone is particularly useful on acid soils, which need regular liming.

Ifiole and utilization: Mg is the major constituent of chlorophyll that has an important role in photosynthesis. Mg also activates different enzymes required in growth processes. It is mobile within plants and could be readily translocated from older to younger tissue when deficiency occurs (Winkler et al., 1974).

Deficiency: The symptom of Mg deficiency begins with chlorosis of lower leaves and progress upwards to young leaves (Christensen et al., 1978). They reported that chlorosis begins at or near the leaf edge and moves inward between the primary and secondary veins and followed by leaf margin burn. The deficiency of Mg is usually observed in light acid soils with low magnesium; in sandy soils with high potassium and calcium content; or following high applications of potassium or ammonium. Mg dcficicncy treatment is probably un- economical in most vineyards. Usually, only a limited number of vines are affccted, and the deficiency does not appear until late in the growing season. Even then, only the basal, older leaves arc usually affectcd. The dcficicncy could be corrected by a furrow application of 800-1600 g magnesium sulphate (Epson salt) per vine. Foliar treatment requires repeated annual sprays of 455 g magnesium sulphate per 100 liters of water. Suspected magnesium deficiency symptoms should be verified by laboratory tissue analysis as the symptoms could be easily confused with those of K deficiency (Winkler et al., 1974) and Christensen et a l, 1978).

Calcium (Ca) Ca-fertilizers are chemical substances containing the nutrient clement calcium in nutrient form of absorbable calcium cations or yielding Ca2 after conversion (Finck, 1582). Soils arc usually amended with Ca to reduce acidity and improve water penetration in soils of high sodium content. Ca has influence on normal metabolic process in plants; it plays an important role in plant nutrition. It is necessary for the continued growth of apical and root meristems; aids in the translocation of carbohydrates, and in nitrogen utilization.

Application: The application of liming materials such as CaCO .CaO or Ca (OH)2 to the soil has two effects (Finck 1982). Firstly, it supplies Ca" and it induces an increase in soil pH due to the alkaline reaction of these compounds, which are needed

[801 The Grapevine for neutralizing soil pH. Raising the pH of acid soils is also a means of providing suitable conditions for the soil bactcria that may influence microbial N2 fixation, denitrification of NO.;- and mineralization of organic soil nitrogen. Secondly, Ca" improves soil structure. Addition of lime to acid soils can reduce exchangeable Al considerably and increase phosphate availability and uptake.

Sources The raw material of Ca-fertilizer is lime found in nature. It is either processed directly into ca-fertilizer or yields Ca-fertilizer after conversion in chemical process (Flinck, 1982). According to Christensen et al. (1978) most important liming materials include limestone (CaCO^. which is 50% CaO), slaked lime (Ca(OH)2. with ”0 % CaO) and burnt lime (CaO, which has 85% CaO)

Ca deficiency? The predominant deficiency symptoms of Ca include: • stem necrosis shortly after verasion: • hollow brown to black necrotic areas on the rachis and its branches; and • circular, dark brown constriction on petioles.

As preventive measure, application of calcium chloride is recommended (Ibid).

The micronutrients The information on all the micronutrients is gathered through a thorough review of the works done by Christensen et al., 1978.

Zinc (Z n ) Zn-fcrtilizers play an important role, especially in areas with frequent Zn-deficiency. Zn dcficicncy, known as the little-leaf disease first identified and corrected as a nutrient deficiency by Chandler and his co-workers in the early 1930s (as cited by Winkler et al., 1974). Zn dcficicncy is the most wide spread micronutrient deficiency of grapevines and ranks second only to nitrogen deficiency in majority grapevine growing areas of the world.

Sources: Zn is available in very small quantity in ail soils except in sandy soils, which have the lowest levels (Finck, 1982). According to Finck, Zn is derived from various weathered minerals and it is adsorbed by clay particles and organic matter, where it will be held in an exchangeable condition. Zn levels are higher in surface soils and often accumulate after being released by decomposing leaves and other plant materials. Soils with pH values of 6 and above affect the availability of Zn. At lower pH, the nutrient becomes more soluble and available. All of the Zn in the soil will become fixed at pFI 9 and soils high in phosphate may also fix Zn in an unavailable form.

Application: Z 11SO4 is the most commonly used fertilizer largely because of its high solubility; but has the tendency to leach easily. Zn chelates arc often used, instead.

[81] Asfaw Zelleke

Role and utilization: Zn is required for auxin biosynthesis, elongation of internodes, and formation of chloroplasts (chlorophyll-containing bodies) and starch. In grapes, Zn is essential for normal leaf development, shoot elongation, pollen development, fruit set and berry development

Zn deficiency: The deficiency may be encountered in limited areas in a vineyard. Application of high-nitrogen fertilizers may accentuate zinc deficiency as dilution effect because nitrogen stimulates total vine growth and thereby increases the Zn needs Deyond the available supply (Alexander and Woodham. 1964) . Likewise, vigorously growing young vines commonly show temporary but mild Zn deficiency due to limited root system and rapid growth. Zn deficiency symptoms may vary, depending upon the evel of deficiency and the variety. Foliar symptoms usually appear following well- developed lateral shoot growth. The new growth on the primary' and the secondary shoots develop smaller but distorted leaves with veins manifesting darker green color, in general the term “little leaf’, is used to describe the appearance of stunted and distorted shoots with closely spaced small leaves under conditions of sever deficiency. Zn deficiency could seriously affect berry set and development thus resulting in reduced yields. Vines deficient in Zn tend to produce straggly clusters with fewer berries that affect acceptability' of table grapes in particular. These v ines may also have shot berries with normal shape, typical of the variety and most of them remain hard and green. The shot berries usually range in size from normal to small and to very- small. In seeded varieties, the small and shot berries have fewer or no seeds than that of normal berries; and shot berries often remain hard, green and fail to ripen (Coombe, 1964). laboratory analysis: Zn deficiency symptoms on leaves and fruits arc simple and easily recognizable. Tissue analysis is usually not needed for diagnosis unless certain questionable symptoms, such as other micronutrient deficiencies and/or certain virus diseases (fan leaf), create confusion with Zn deficiency. Soil analysis for Zn is not a reliable method of determining the need for Zn in a v ineyard. The Zn level in the soil may not be correlated with that of the vine because of differences in the response of grape varieties to the effects of low Zn levels. Furthermore, the grapev ines have extensively deep root system that enables them to maintain a satisfactory Zn level even though the soil content is considerably low. The Zn level in the grapevine reflects all of diese variables, and hence tissue analysis may not be preferable over soil analysis.

Application: Once the deficiency has been diagnosed, the recommended methods of treating the vines are foliar spraying, daubing, soil application and injection with the recommended type and rate of Zn-nutrients as reported by Christensen et al. (1978) and others. The methods include the following.

Foliar spraying: Foliar spray is usually applied on cane-pruned vines because the movement ofZn in the vines is not limited. Foliar sprays may also be used on spur- pruned varieties if the dcficicncy is mild. In cases of severe deficiency however, it may

[82] The Grapevine be advisable to apply a foliar spray coupled with daubing treatment for either of the pruning method. Zn sprays should be applied two or three weeks prior to bloom for improving berry set The vines should be sprayed thoroughly covering the flower c ustcrs and the lower surfaces of the leaves. Christensen and his coworkcrs suggested a single spray, if foliar symptoms does not persist or reappear later in the growing season. Otherwise, a second application may be needed. Zn solution could be prepared by mixing 450 g of zinc sulphate (36 percent Zn) and 340 g of spray lime in 100 liters of water. The lime will neutralize the acidity and prevent leaf burn. Add suitable wetting agent to ensure diorough wetting of flower dusters and leaves.

Daubing: Daubing or painting is the most common and successful treatment for sour pruned vines. Painting all the fresh cut ends with a solution of zinc sulphate will facilitate uptake and prevent washing off the zinc applied. Spraying or daubing should be postponed until a soaking rain or irrigation water is applied. For best results, prune the canes at about 1 - 2 cm above the top node and daub after pruning. The solution snould be prepared by slowly adding zinc sulphate to water, stirring rapidly to ensure complete solubility. Use a short stick padded with a sponge or absorbent cloth at one end to daub the cut ends. Delay daubing until desiccating winds or unusual, prolonged cold spells is cleared (Winkler et la., 1974). Under unfavorable conditions, vines may absorb the Zn solution in amounts that could damage the buds and spurs.

Soil applications: Zinc sulphate could be placed in the form of band in 20-25 cm deep furrows about 45 cm away from the vines on either side of the rows during the dormant season. The suggested rates arc 450 g per vine for young and 900-1350 g for matured ones. Zn - EDTA (chelates) have also been used successfully with furrow applications at rates of 14-28 g elemental Zn per mature vine .

Soil injection: Zinc sulphate solution could also be injected deep into the soil. Injections are made at about 30 cm from the vine trunk, during dormancy. For young vines, 15 to 30 g zinc sulphate per vine can give satisfactory correction of deficiency. A suggested concentration of 450 g zinc sulphate in 100 liters water has been found useful.

Boron (B ) t appears that the grapevines have a higher requirement for boron than most other perennial crops (Winkler et al., 1974). The narrow range between deficiency and excess levels of boron makes it quite unique among the micronutrients. It requires a fraction of one part per million in the soil solution for sufficiency while higher parts per million could be toxic according to Winkler and his group. Deficiencies that affect vine growth and fruit set have been noted primarily on sandy and alluvial soils of granitic origin.

Source: Borosilicate minerals that arc resistant to weathering are believed to be the sources of B-fertilizer. Most of the available B is held by the organic and clay fractions in the soils through an anion adsorption. Thus, they are released slowly and arc less

[83] Asfaw Zelleke subject to leaching than other neutral or negatively charged plant nutrients (Finck, 1982). Organic manures such as garbage and composts with high ash content contain substantial amounts of boron ( 1 0 0 ppm) and could serve as boron amendments albeit their use is associated with the risk of overdose according to Finck.

Utilization and role: B-fertilizer play significant role in cell division, new cell differentiation, in regulating the carbohydrate metabolism in vines. Vines take up B as borate ion. In the grapevines, low B level affects fruit set by limiting pollen germination and normal pollen tube growth. A continuous supply is necessary for normal growth and productivity of quality grapes.

Application: The methods of application of' B-fcrtilizer vary on the size of the vineyard. Commercial vineyards are treated by spraying the soil while smaller sized vineyards are treated by broadcasting the materials at about 30 to 90 cm away from the vines. The narrow differences of concentration in the soil at which neither deficiency nor toxicity occur is a problem of great concern. Band or foliar application of B is often more efficient in correcting B deficiency than broadcast application. Crops differ in their sensitivity to B deficiency (Cook. 1961). According to Cook, B deficiency in ihe grapevines is one of the most severe non-parasitic diseases because fruit formation is impaired and yield depression as high as 80% may occur compared with plants adequately supplied with B.

.Deficiency: B deficiency could be identified as a temporary early-growth period deficiency and early-to-mid-growth period deficiency (Cook, 1960). According to Cook, the early-growth period deficiency includes stunted and distorted shoot growth with bushy like appearance. The growing tips may die on severely affected shoots, which become unfruitful or have underdeveloped dusters. Severely affected leaves are somewhat fan-shaped and show interveinal chlorosis. The early-to-mid-growth period deficiency symptoms appear at blooming and hence affect berry set and development. Clearly distinct symptoms are always accompanied by pronounccd symptoms on fruits, because pollination and fruit set are the physiological processes and so severely affected vines may have no crop. Some clusters may dry around bloom time, leaving only cluster stems (rachis). Clusters may include some normal size berries as well as shot berries with distinct uniform size and shape. However, shot berries caused by low B level should not be confused with those caused by zinc deficiency, which are more varied in size than those affected by B deficiency. Occasionally, in B-deficicnt vines, clusters that appear to set at bloom time shatter severely at about mid-growing season. V in e y a r d s even with only a few vines showing symptoms should be treated to avoid progress in symptoms. Bloom time petiole analysis is recommended to verify B dcficicncy.

Materials: several B fertilizer sources containing different amounts of actual B content are available. Common borax, with 34 % boron trioxide (B2O3 ) can be used. Other boron materials, which vary from granular or coarse to fine powder and differ in solubility, are used as fertilizers; they range from 44 to 68 percent B2Ov Any of these

[84] The Grapevine materials is satisfactory for direct soil application, however, only a finely ground B source material should be used for foliar application according to Cook.

Fates: B-spray material containing 34 to 48% B2Ch should be applied at 14-17 g per vine (soil), or 30-31 kg/hectare.

Application methods: Methods of application depends on the size of the vineyards. Small vineyard can be easily treated by hand broadcasting the material at about 30-60 cm away from the vine. Whereas, spraying the soil is the most accurate method of treating larger vineyards. For soil spray application, it is necessary to determine the required amount (liters) of a B spray material per hectare and then dissolve the correct amount in the tank. It is essential that instructions on using B fertilizer materials should be followed closely, because higher than recommended rates could cause toxicity.

Time o£ application: B fertilizer can be applied any time, when the soil is quite moist or just before irrigation. However, under Ethiopian condition early dormant time application provides for maximum exposure to rainfall to help move the fertilizer into the soil. lion (Fe)

Importance: The majority of Fe-fertilizers are water-soluble. They exist as salts or organic complexes known as chclates (Finck, 1982). They are mostly applied as foliar nutrients. Iron deficicncy is the tliird most important micronutrient problem after zinc and boron in most vineyards of the world. The deficicncy is mostly temporary, its occurrence does not appear to be of any economic importance, unless the location of the vineyards has some problems. Grape varieties vary in susceptibility to Fe deficiency. Vines with a weak root system rarely show a higher incidence of chlorosis, particularly under conditions of over cropping. This problem is most common in some grapevines varieties that had heavy cropping in the previous season.

Availability and uptake: Fe-fcrtilizcr is available in soils as oxides, lydroxides and phosphates. During the weathering of these minerals, small amount of Fe is released and are absorbed by roots in the ionic form or as complex organic salts chelates). Utilization of Fe is limited by the condition of the soil rather than the total Fe levels in the soil. Soils that are high in phosphate and in lime, affect uptake of Fe. High carbonatc or lime content in the soil can cause immobilization or inactivation of Fe. Poorly drained heavy soils can increase the problem of Fe availability and could affect its uptake by roots.

Application: Inorganic Fc salts rapidly become insoluble as oxides. Addition of these salts to the soil is mostly without effect. Iron chelates are more effective fertilizer and can be used as a soil additive or as a foliar spray. In soil application, it is important to consider the stability of the chelate particularly in relation to the soil pH. At higher

[85] Asfaw Zelleke soil pH, soil Ca" present in higher concentration can displace Fe' from less stable chelates giving rise to a Ca-chclatc that might precipitate Fe-oxide thus making the Fc unavailable.

Utilization and role: Fc moves in plants as ferrous ion (Fe") to the site of utilization. It is combined with proteins to form complex organic compounds. It does not move freely from one tissue to another in plants: the deficiency symptoms appear first in the newly developing and expanding leaf tissues. Much of the Fe in plant tissues is transformed into unavailable forms. Thus, there is little correlation between total Fe content and deficiency symptoms. Activation of the enzyme system is the major role of Fe-fertilizer in the plant system. A shortage of usable Fe also impairs chlorophyll synthesis leading to development of Fe chlorosis and reduction in growth and development of plants.

Deficiency: Foliar symptoms of iron deficiency first appear on rapidly expanding young leaves as pale yellow leaves and green network of veins. As die deficiency Decomes more severe, most of the leaf areas turn yellow and then white. Severely iffected shoots and flowers reduce in growth. Cluster stems may turn pale-yellow and fruit set can be poor on such shoots.

Correcting deficiency symptoms: Two types of treatments arc available to correct Fe deficiency symptoms. These are foliar spray treatments and soil treatments. Foliar sprays treatment can be used as iron chelate or ferrous sulphate as per the recommended rates and time. The spray should be repeated as deemed essential at 10- to 20-day intervals. Soil treatment can be used where Fe deficiency is severe. This system however has limitation because of high cost. Fe-EDDHA (ethylenediamine cli(0-hydrozyphcnyl-acetic acid) chelate can be used in high lime or alkaline soils.

Manganese (Mn) Manganese is one of the important micronutrients involved in enzymatic reactions in green plants. It is almost never limiting to plant growth in soils (Salisbury and Ross 1978).

Sources: Mn-fertilizers are derived from the decomposition of fcrro magnesia rocks and exist as Mn-sulphate (soluble) and Mn-oxides (insoluble) each of which serve different purposes (Finck, 1982). The soluble forms that include manganous nitrate |Vln(N0 3 )2 | and manganous chloride (MnCF) are suitable for leaf fertilization. Mn- carbonate or Mn-phosphate is also used as fertilizer after suitable processing. The insoluble form (MnO) serve as soil dressing to replenish reserves. Mn-fertilization ( ike Fe-fertilization) is problematic since deficiency is not frequently due to soil impoverishment, but to fixation of the abundant reserve in the soil.

Application: Most soils contain adequate levels of available Mn so that its applications may not be necessary.

[86] The Grapevine

Utilization and role: Plants take up Mn primarily in the form of manganous ion (Vln"). Mn serves as an activator of several enzymes involved in growth processes. It is involved in the splitting of water molecules and in evolving O: in Hill reaction, and in chlorophyll formation. Availability' of Mn-fertilizcrs is affected by soil pH. It increases with the lower pH values. i^eficiency; Mn deficiency is observed more often in alkaline, sandy and Mn poor soils (Finck. 1982). Lower leaves turn pale followed by the appearance of small yellow soots with a mosaic like arrangement. Growth of shoots, leaves and berries are affected lis deficiency advances and. cluster maturation gets delayed. Mn deficiency symptoms appear shortly after bloom on severely deficient vines. The symptoms begin on the basal leaves as chlorosis between the veins. According to Christensen et al. (1978), increasing chlorosis develops between the primary and secondary veins; the veinlets tend to retain a green border. According to Christensen and his coworkcrs. the difference in the deficiency symptoms among Mn. Zn and Fc are quite distinguishable, "hat Zinc deficiency symptoms first appear on newer growth and includc some leaf malformation. Iron deficiency also appears on newer growths and causes a much finer network of green veins in the yellowing leaf tissue. In manganese deficiency, chlorosis first appears on basal leaves, but it is more extensive between the primary and secondary veins, developing to complete yellowish bands. Laboratory analysis of ,'ietiole samples from affected leaves and from normal leaves should be used for final diagnosis.

Correction of deficiency symptoms: Mn deficiency symptoms usually appear late in the season on older leaves thus contributing little to vine function with less effect in reduction of leaf chlorophyll and photosynthesis. For deficiency correction, it is recommended to spray manganese sulphate as per the manufacturers’ recommendation. It is worth noting that the type of fertilizer to use is usually based on soil analyses. In general, recommended fertilizers should be applied selectively.

Summary

t is apparent that some local soils, even some of the existing vineyards arc likely to show nutrient deficiencies. Available phosphorus and the micronutrients Zn, B, Fe and vln directly or indirectly play significant role in growth and development of grapes. Phosphorus and zinc nutrients should be given specific attention since these elements arc shown to be one of the main factors influencing bud fertility of grapevines. Despite his fact, very little attention is given to studying the role of micronutrients in all crops n Ethiopia. Therefore, these specific nutritional problems and the practical remedies are addressed in brief based on information from reviewed sources albeit the equirement of fertilizers for the grapevine can be different between temperate and tropical or sub-tropical conditions.

Manure has been in use globally as a fertilizer since time immemorial. The nutritional value of manure and other organic fertilizers has been well understood locally but

[87] Asfaw Zelleke

their specific nutrition values for the production of grapes need to be assessed and verified through research. However, the amount of fertilizer desired and the amount that the vine takes from the soil and the nutrient content of the different sources of organic fertilizers as manure have been obtained from the literatures and presented in Tables 12 and 13, respectively.

Table 12. Estimated nutrient requirement of grapes under tropical conditions*

Productive cycle Vegetative cycle Nutrient (kg/ha) (kg/ha) N 60-80 30-40 P2O5 15-20 5-10 K2O 50-70 10-15 MgO 12-18) 8-10 CaO 35-45 10-12 ‘ Adapted from Schaller(1986) and Lohnertz (1989)

Table 13. Nutrient content of different organic fertilizers

Fertilizer Normal Nutnent (kg/ha) Organic rates (t/ha) N P2O5 K2O CaO MgO material (kg/ha) Livestock manure 60 120 180 360 300 72 10 200 Poultry manure 10 100 280 160 380 40 6 000 Pomace (grape) 10 40 36 130 75 20 4 000 Straw 5 -- 75 25 50 4 500 Sewage sludge 30 30 36 120 1200 150 5 200 Adapted from Schaller (1986) and Lohnertz (1989). N: Available amount in growth cycle of application: in following growth cycle 80-100 kg/ha: K2O: Immediately available: P2O5: Total- P - content Laboratory Diagnostic Methods Soil and plant tissue analyses are essential to determine the nutrient requirements of the grapevines. The two methods are briefly discussed based on the information obtained from Christensen et al. ( 1978).

Soils analysis Soil analysis in the laboratory is used to assess vineyard problems related to nutrient deficiency, salinity, toxicity and pH. Soil analysis is recommended depending on anticipated problems using saturated soil paste or saturation extracts. Saturated soil paste is used to determine saturation percentage (SP) - a rough measure of soil texture, and pH -a measure of acidity or alkalinity. Solution extracts run is used to analyze the following.

•* Elcctrical conductivity (ECt.) - measure of salinity >» Exchangeable sodium percentage (ESP) - to evaluate the sodium toxicity and soil permeability hazard <* Boron (B) - to test for toxicity

[88] The Grapevine

» Gypsum requirement (GR) - to estimate the amount of gypsum to reclaim a sodic soil • Lime requirement - to estimate the amount of lime needed to adjust the pH of an acid soil

Plant tissue analysis Plant tissue analysis is much more effective and reliable than soil analysis. The analysis represents the concentrations of nutrients the grapevine is able to remove from the soil. The leaf petioles or the leaf blades are used for tissue analysis.

How to sample a vineyard The sampling method of vineyards depends on the objective of the analyses and these are presented as follows.

A. To determ ine the general nutritional levels 'his approach is used when surveying a vineyard for fertilizer needs or when evaluating a fertilizer program. It requires the following considerations.

• Time to sample. Timing is extremely important. Samples must be taken during blooming- the nearer to full bloom the better. (“Full bloom” is taken when approximately two-thirds of the caps have fallen from the flowers). This usually occurs in December in the Ethiopian highland areas depending on specific location and variety. • Plant part to sample. The petioles from leaves opposite the clusters toward the base of the shoot are normally used. Remove and discard the blade leaving only the petiole for analysis. • Taking a representative samples. Each sample should represent not more than 4 hectares even in uniform vineyards. However, areas of different soil types and with weak or strong vines should be sampled separately. Each sample should consist of 75 to 100 randomly sampled petioles i.e. one petiole per vine from uniformly distributed vines over each area. • Care of samples. Put each sample in a clean paper bag (do not use a plastic bag because of possible moisture condensation and molding). Label each sample (name/variety, date, location and condition of vineyard and foliar application if used). Deliver samples to the laboratory immediately. If there is a delay, keep the bags open in a warm. dry', well ventilated place (to prevent molding). Foliage contamination from a nutrient spray can give erroneous laboratory results. It is therefore, not recommended to sample after a nutrient spray unless any nutritional element contained in the spray is to be considered, or prior arrangements have been made with the laboratory for sample washing.

B. To determine troubleshooting, diagnose disorders and follow up sampling

• Time to sample. Samples can be collected whenever disorder appearance is noted. For an area with a questionable nutrient level during a definite stage of growth, it is best to sample al bloom time or at berry softening. However, bloom

[89] Asfaw Zelleke

time offers the advantage of easy and uniform sampling. Both deficiency and toxicity symptoms most commonly appear in midseason or at harvest time. Thus, sampling at this time is useful to diagnose vine disorders and to follow up on questionable nutrient levels.

• Plant part tio sample. Take the petiole from the most recently matured leaf on a shoot after the bloom period. This would be the first fully expanded leaf, usually the fifth to seventh leaf from the tip of an actively growing shoot. To diagnose toxicitics. collect both the leaf blades and the petioles for separate samples, because greater amounts of elements like B may accumulate in the blade itself.

• Taking a representative samples. Sample the area in question uniformly taking representative samples in all cases Where leaf symptoms arc observed, sample the affected leaves and take a second sample from healthy shoots in unaffected area for comparison.

• Care of samples. Same as in A above.

What analysis to run Bloom time petiole samples laboratory analysis for nitrate-nitrogen (NO3.N), total phosphorus (P), total potassium (K), zinc (Zn) and boron (B) should be run for general nutritional surveying. Analysis of other elements such as magnesium (Mg), and manganese (Mn), w'hich are rarely at deficiency levels, is only necessary for more background information or for leaf symptoms disorders diagnoses. Samples can be analyzed for possible toxicitics of chloride (Cl), boron (B), or sodium (Na), or for possible potassium (K) deficiency in mid (December to late February) growing season.

How often to do the analysis Check the bloom time nitrate-nitrogen levels for a few successive years so that any necessary adjustments can be made in the nitrogen fertilization program to establish correct vine nitrogen levels. If levels of other nutrients are adequate, rerun every few years to maintain a check.

Interpretation of laboratory results 1 : is important that laboratory results are critically interpreted to assess the values for grapevine nutritional element requirements. The status of each nutrient clement is presented in Table 14 along with the respective nutrient element’s corresponding values that arc present in the soil. Christensen et al. (1978) is the source of the information in the table. It is important that the status of these nutrient elements be identified as a major part of the research strategy of all research centcrs in the future. Critical levels arc not yet known for all grape varieties, until then and the levels presented in Table 14 can be used as a guideline.

[90] The Grapevine

'able 14. Different levels of macro-and-micro nutrient elements in vine tissue of some grapevine cultivars

Status of nutrient Macronutrient levels N03 - N (ppm) Total P (%)* Total K (%) Total Mg (%) Deficient <350 < 0.01 <1.0 <0.2 Questionable 350 -500 0.10-0.15 1.0 -1 .5 0 .2 -0 .3 Adequate 500- 1200 0.16-0.18 >15 0.4 - 0.6 Excessive >2000 --- Possibly toxic >3000

Micronutrient Zn (ppm) Mn (ppm) B (ppm) Fe (p p m )" Deficient < 15 <20 <25 Questionable 15-26 20-25 26-30 Adequate 2 7 -3 0 2 6 -2 8 3 0 -5 0 Excessive/toxic -- 100-150 Possibly toxic -- >300 (leaf) Source : Christensen et al. (1978) ‘The levels probably will decline by the mid of the season. ** Critical level has not been established yet; no correlation found between Fe deficiency and tissue levels

[91] Asfaw Zelleke Chapter VII

Problems of Production

n cultivating grapevines, a numbers of production problems are stated elsewhere. IThe major ones that are serious in Ethiopia are the following. Abiotic Stress

Grapevine cultivation The Temperate Zone is the home of the grapevines. In recent years, the cultivation of the grapevine in tropical/subtropical areas showed a remarkable success. This could be attributed, at least in part, to the relentless efforts made by viticulturists to develop cultivars that have low chilling requirement. The application of certain horticultural practices to induce bud dormancy also made immense contribution towards adaptation of cultivars to the tropics. The problem of grape production in the tropics is mostly a function of environment, which affects sustainable productivity through maintenance of bud fruitfulness.

Bud fruitfulness Grapevine cultivation differs considerably in their bud fruitfulness. Some cultivars have fruitful basal buds whereas some other cultivars tend to have these buds on either the middle or top part of the canes. Some cultivars are also erratic in both the number and the form of the clusters that are produced than others. The process of fruitful bud and inflorescence formation within the grapevine buds is a unique phenomenon. The pruning system followed in tropical countries should consider potential fruitful bud position to be able to maintain fruitful buds intact and ensure sustainable productivity . As discussed in Chapter I. the flower cluster primordia are formed at blooming time during the season in the preceding year (temperate /one). In other words, the potential amount of fruit in the current year is already determined last year. It is of special importance to know if this is also true under tropical conditions, where low fruitfulness is a common problem, and where productivity decreases continuously if pruning is not applied properly. During the growth of the shoot after pruning, rudimentary leaves are formed in the developing bud located in the axils of the leaves. Group of cells are produced and differentiation proceeds (Winkler et a/.. 197 1). Differentiated cells grow into flower cluster and subsequently into a fruit. However, differentiation of cells to a certain extent is retarded at the base of the shoot. The formation of fruits in the buds depends on various internal (hormonal) and external (temperature, light intensity, photoperiod, carbohydrates and nutrients) factors (Pratt, 1971). According to Pratt, in the temperate /.one, the process of fruit primordia development starts in basal buds aboi.t two weeks before bloom of the visible cluster on the shoot and proceeds almost until harvest. At this stage, the total number of potential flowers for next season crop [921 The Grapevine has already been decided. There is continued competition for carbohydrates, light, and nutrient between the developing bud, the developing fruit, and the vegetative growth. The vegetative growth is reduced and ceases completely before the onset of ripening of the fruit (verasion) and then shoot starts to mature. Thus, one competing sink for carbohydrate and nutrient is removed or weakened. This leaves more carbohydrate and nutrient for the buds. Wood maturation and storage of reserve continue for a long period after buds are completely developed. Many of the processes occurring one after another in temperate zones occur simultaneously in the tropics even though shoot growth does not slow in the latter (Schutlz and De'try. 1990). Consequently, in the tropics reserve is hardly formed and the buds will be disadvantaged throughout the growing season. However, fruitfulness of grapevines is improved by relatively high temperature (25

Motic Stress

Diseases The influence of diseases on grape production is found throughout the history of viticulture. Diseases affect growth, production, harvesting, processing, marketing, and the consumer. They lower quality, increase the cost of production and vineyard efficiency. Some of them debilitate while others depending on severity kill vines and destroy vineyards locally and over large areas/regions. Catastrophic diseases alter cropping pattern, exert long-term effects on local, and export markets. Diseases are endemic, i.e., native, prevalent, and well established (Magarey. 1985). The problem of diseases is influenced largely by the prevailing weather conditions. Under favourable weather for development of diseases, epidemics may occur w ith considerable losses. Prolonged periods of wet weather favour Bolrylis bunch rot. dow ny mildew and other leaf and fruit diseases (Pearson and Goheen. 1988). Thus, under humid growing conditions, disease infestation, except for powdery mildew, is much more severe but can be controlled with continuous chemical sprays albeit it may not be economically feasible. This is especially true for downy mildew and bacterial diseases. So far. the most common and frequently occurring diseases in most local vineyards are the powdery mildew (Uncinula necator) and downy mildew [Plasinojxira vitico/a personal observation)]. The damages caused by these diseases are quite high and may lead to total crop loss if proper and timely control measures are not applied. The extent of severity of each however depends on the location and environmental factors.

[93] Asfaw Zelleke

Powdery M ildew ( Uncinula necator)

The powdery mildew also called Oiiiium is regarded as one of the most important fungal diseases in all the grapevine-growing countries. It is by far, the most troublesome disease, especially during the dry season. It infects green parts at any stages of plant growth (Built and Lafon 1978). The warm weather in the tropics favors the appearance of Oidiwn. Moisture does not seem to be of great importance to the fungus proliferation at favorable temperatures (21 32°C). since it grows well under very dry conditions (Built and Lafon, 1978; Sail and Teviotdale, 1988). Spores do not germinate above 35°C. The disease develops much more abundantly in the shade or diffused light than under bright light situations. Vines forming dense canopies are more prone to severity of the disease than those with fewer canopies are.

Symptoms: The fungus attacks all green parts of the plant, at first producing a very fine, light, translucent, cobweb-like growth radiating from the spot where the spores grow. Soon the patches assume grayish, powdery appearance, caused by the formation of numerous spores. Affected areas later darken to reddish brown or black. Severely affected young leaves become distorted and discolored. Flowers when attacked fail to set fruits; small berries may drop off: while large berries develop into abnormal shapes. K I Control: Control of powdery mildew in commercial vineyards is generally using fungicides. Thus, the pathogen can be controlled by both prevention as well as eradication. The most effective and most reasonable control practice is to prevent the development of powdery mildew.

Prevention: Sulfur dusting gives excellent protection. This however requires good coverage of green foliage and fruit with a very line coating of sulfur dust throughout the season. The extent and efficiency of protection will depend upon the timing of applications and thoroughness of coverage. This approach, however, will only be successful during the dry period. For best results on larger farms, a good dusting machine to mix sulfur dust with the air and give good uniform distribution over the vine foliage is recommended. Moreover, the vines should be well trained so that dust will penetrate through the canopies. For effective control, fungicide spray should start just after bud burst (Emmett el a/., 1984). They reported that for most varieties dusting should be timed when the shoots average 12-15, 25-30. and 40-45 cm long. The first three dustings are very important and should be an integral part of the program. Further applications are necessary at weekly or fortnightly intervals depending on disease pressure until fruit begins to ripen for wine and raisin grapes. Table grapes require dus ing until harvest to prevent infection of the cluster parts. Sulfur applications should be done immediately following bad weather. Application has to be repeated if the sulfur has been washed off, which constitute the biggest disadvantage of this method. Sul ur may not be effective below I8°C and above 30"C as the risk of phytotoxicity may increase greatly at higher temperature. Once the mildew fungus has infected the plant parts and started producing spores, the applications are no longer effective.

[94] The Grapevine

Dusting should be done early in the morning or late in the afternoon. This prevents leaf burning by sulfur when applied in hot weather.

Eradications The powdery mildew fungus is no longer prevented by sulfur dusting after it establishes on the vine and starts producing spores (Delp, 1954). It is therefore essential to use an eradicant spray (chemicals that have curative qualities) such as wcttable sulfur, karathane, triadimefon, and benomyl triadimefon penconazole to kill the fungus. The eradicant spray solution should be prepared following the manufacturers’ recommendation. However, the foliage has to be thoroughly wetted on both the upper as well as lower surfaces of the leaves, the canes, and the fruit. For average vines, it requires 2000-3000 liters of spray solution per hectare early in the season and 3000-4000 liters during mid to late season depending on the equipment used (Emmett et al., 1990; Schultz and Dctry, 1990). Triadimefon (Bayleton), a systemic fungicide, is used in most vineyards of Ethiopia to keep powdery’ mildew under control. The chemical is very effective but expensive. The advantage is that it docs not need repeated application as frequently as sulfur, which is of significant importance during the rainy season. Application every 2 weeks or more at the rate of 1 g per liter (1 kg/ 1000 liters of water) is adequate (personal observation). Both sulfur as well as Bayleton have the advantage that they do not affect predatory mites feeding on grape pest, the spider mites. This is important in view of aiming at an ecological oriented pest management. Karathane and Benlate, should not be used to control Oidium because of possible side effects. Karathane has been found to kill predatory mites and to favor the buildup of spider mite populations. Use of Benomvl, is also discouraged since this chemical was found to bring up resistant fungi strains of another grape fungal disease, the bunch rot or grey mold or Botrytis rot caused by Botrytis cinerea.

Downy Mildew ( Plasmopara viticola ) Grape downy mildew occurs in warm and wet regions during the vegetative growth period of the vines. The absence of rainfall and insufficient warmth during the growth period limits the spread of the disease . Warm dry weather is unsuitable for disease development. It is present in all grapevine-growing regions of the world. Humidity, frequency and duration of rain or heavy dews during the growing period influence the evel of intensity of infection of vines. Downy mildew attacks all varieties of Vitis vinifera. Under tropical conditions, downy mildew is a serious problem as the required moisture and temperature for the incidcnce and spread of the disease arc present :hroughout the year.

Symptoms: fungus attacks the green parts, particularly the leaves. It attacks first ;he older ones and spread to the shoot. The symptoms includc light yellow translucent spots on the leaves, causing them to dry, crimplc and drop (Magarcy et al., 1985). Succulent shoots, petioles and tendrils may also be attacked and show water-soaked and slightly swollen appearance which later on covered with a downy growth of the fungus. Flowers and fruits could be attacked and killed, which fall from the cluster. Leaf infection is the most important as a source of inoculums for eventual berry infection. Infected shoot tips thickcn, curl and become white with sporulation. They

[95] Asfaw Zelleke

eventually turn brown and die. Similar symptoms are also seen on petioles, tendrils and young inflorescences, when attacked early enough, ultimately turn brown, dry up and drop. The young berries are susceptible, appearing grayish when infectcd (grey rot) covered with a downy felt fungus of sporulation. Berries bccome less susceptible as iiey mature but infccted matured berries remain firm as compared to healthy ones. The nfectcd berries drop easily, leaving a dry stem scar.

Control: downy mildew infection occurs during rainy periods. It can be controlled by preventive spraying. A number of fungicides, such as zincb, maneb captan, mancozeb, metiram, and several others have been used successfully in many countries. Organic copper fungicides viz “Bordeaux-mixturc”, copper oxychloridc, cupric hydroxide have long been used for the control of this fungus (Margarey, 1985; Margarey et al., 1985). Copper-based applications, however, have been shown to delay ripening. Sprays for powdery mildew and downy mildew can be combined (personal observation at Debre Zeit Agricultural Research Centre. DZARC). During the rainy season, spraying every 7-10 days may be necessary if some organic coppcr fungicides arc used. Time interval between can be increased with the use of systemic fungicides such as Mescnoxam+Mancozeb (Ridomil). The use of Ridomil at the rate of 2.5 g per liter (2.5 kg/1000 liter of water per hectare) has been found effective at Debre Zeit Research Center at an interval of two weeks. In other countries, however similar results have been achieved using potassium phosphate. This fungicide is easy to prepare by mixing about 800 g of potassium hydroxide and 10 0 0 g of phosphoric acid in 10 0 0 liters of water. Potassium-phosphate has also been shown to control other fungal infections such as Phytophthora root-rot. It can be combined with wcttable sulfur for spraying against downy and powdery mildews. The use of Dithane, recommended for grape- downy mildew control has the disadvantage for it kills predatory mites. On long-term control measure, adoption of biological control should be emphasized. However, the test strategy would be the planting of resistant varieties.

Itotrytis Bunch Rot {Botrytis cinerea) The Botrytis bunch rot also known as gray mould is a serious problem in all countries of grapevines culture. It reduces quantity and quality of the crop. The reduction in yield is associated with premature drop of bunches or with loss of juice and desiccation of berries. In table grape production loss of fruit quality in the field, in storage or transit can be substantial ( McClellan and Hewitt, 1973; Sail and Teviotdalc, 1981). In wine production, the most serious damage is qualitative from the altered chemical composition of diseased berries. Wine produced from affected grapes have off-flavor and become sensitive to oxidation and bacterial contamination, rendering them unsuitable for ageing (Singleton, 1975). However, in certain cultivars and especially under certain climatic conditions Botry’tis infection of grape cluster takes on a particular form known as "noble rot." This rot is beneficial and contributes to the production of exceptionally sweet white wines: the most prestigious of which are the Tokays in Hungary, Sauterous in France; Austlese, and Becrenauslesc in Germany.

[961 The Grapevine

Sym ptom s; Botrytis bunch rot attacks both the vegetative and reproductive tissues. In the early growing season, infection occurs on the young shoot, leaves and immature inflorescence, which leads to shriveling of berries and abscission. Free moisture on the surface of the fruit, following rain or cracked berries, is most conducive to infection, though infection takes place readily in an atmosphere of very high humidity. Following verasion (ripening), the fungus enters the ripening berries (through the epidermis and wound). Its severe outbreak is closely correlated with the incidence of rainfall during pre-harvest.

Coaatrols there is no satisfactory control available. Copper sprays are frequently used alternatively with Captan, and other specific botryticidcs such as Ronilan or Rovral. The use of sodium silicate also shows some promising results. However, all these chemicals exert only a limited control. To minimize the danger of infection, the training system should be adopted to ensure good aeration and rapid drying of the fruit after rain. Removing the basal leaves on the shoot 3-4 weeks before harvest is also beneficial. Susceptible cultivars should be protected against bunch rot by applying sound cultural and chemical control measures (Nair, 1985) that includes the following.

® Avoid excess vegetative growth through judicious use of nitrogen fertilization; o Increase aeration and exposing of cluster to sun by using appropriate trellising system and by removing leaves around the fruit and; ® Apply sound protection measures against diseases and insect pests.

Chemical control should be carried out as a preventive treatment. This usually follows a standard program of four spays at different stages of vine growth (Nair, 1985). The Irst one, at the beginning of fruit set; the second treatment just before berry' touch; the third one at beginning of verasion (ripening) and the fourth treatment at about three weeks before harvest. Proper adjustment of spraying equipment is essential in order to give consistently good penetration and spray coverage of cluster. Bunch rot in stored table grapes is controlled by sulfur dioxide fumigation combined with storage emperature at 0°C. Under normal conditions, this disease is not of much significance n the highland areas of Ethiopia with high precipitation during the rainy season produces no crop. They produce only a single crop annually. Unless unexpected heavy ainfall occurred at pre-harvest time (dry season) in these areas, the incidence of Bottytis is minimal. Vineyards where two crops (such as Merti and Zewai) are harvested annually, the intensity, duration and amount of rainfall is not high enough to promote the incidence of Botry'tis infestation.

Anthracnose ( Gloeosporium ampelophaguni) Anthracnose is a disease of rainy, humid regions where it is practically impossible to grow some grape cultivars (Mirica and Mirica, 1988). Temperature and moisture are the main environmental factors influencing disease development. The spores of the fungus are disseminated by rain and dew. It is present in all grape-growing regions receiving rain during the growing season. It is not serious unless rains are frequent in the growing season. Anthracnose reduces the quality and quantity of the crop besides weakening the grapevine. [97] Asfaw Zelleke

Symptoms; Young leaves are most susceptible to infection, according to Mirica and Mirica, circular leaf lesions (1-5 mm in diameter) with brown to black margins and round or angular edges are observ ed. The center of the lesions becomcs grayish white and dries. Necrotic tissue eventually drops out of the lesion, leaving a shot-hole appearance. Clusters are susceptible to infection before flowering and until verasion. Lesions on berries are surrounded by a narrow, dark brown to black margin.

Control: Phytosanitary regulation prohibiting transport of infected propagation materials should be practiced. Treatment can be similar to that for downy mildew. Spraying has to commence shortly after leaf - out during the rainy season when disease pressure is high. During the dry season, anthracnose is less of a problem. Spraying vineyards at the time of leaf emergence with thiophanate methyl (0.1 %), bitertanol < 0.1%), benomyl (0.1%), carbendiazim (0.1%) or Boreaux mixture (0.8 % ) are found helpful in disease management. At least four sprays during rainy season at fortnight intervals are required to reduce primary inoculums during the growing season.

]&aisin moulds and rots The disease occurs in association with wet weather and the amount of mould and rot varies with the vineyard, stage of maturity at harvest and the season (Hewitt, 1988). This disease reduces production, increases the cost of production and processing of raisins and reduces quality. Raisin with rot is a total loss; the rot cannot be removed by washing.

{Symptoms: Moulds are mostly contaminants (Hewitt, 1974). Mould fungi grow on the surface of raisins, produce conidial spore masses. Rots are caused by fungi colonizing the inside of the berry before harvest or during drying. Fungi growing inside the raisin form mats of mycelium and sporulation tufts on the surface.

Control: Prevention and chemical treatments are most effective control measures. Cultural practices such as adjusting crops should be adapted to obtain high soluble solids. This can be done through berry or eluster thinning/removing so that the parts remaining arc better nourished and fruit set is thereby increased giving more mold-free bunches and berries, and better yield with high soluble solids. Crop can also be adjusted by thinning over-compact bunches to attain looser bunches, large berries and to reduce the risk of bunch rot at harvest (Martini, 1966). liacterial diseases Crown gall: This is a disease, which manifests overgrowth on trunks and arms of vines. Today, crown gall of grape is a serious problem of in regions where, Vitis vinifera grapes are grown and prevailing climatic conditions favor freeze injury, thereby providing wounds predisposing the vines for infection. The gall is caused by die organism Agrobactrium tumefaciens (Lehoczky 1968, 1971; Teviotdale and Schrodi, 1988).

[98] The Grapevine

Symptoms: flesh galls are produced in response to infection. Galls are found on the lower trunk of vines near the soil line or slightly below the soil surface. Aerial galls may extend more than one-meter upwards into the trellis.

Control: it has been successfully controlled on some hosts with biological treatments using Strain K1026 of Agrobacterium radiobacter (Ophc / el al., 1990). It is capablc of producing an antibiotic inhibiting the pathogen and with an eradicant chemical. The planting of pathogen-free vines is the most effective way to manage the disease. The use of shoot tip culture is also effective to eradicate .4. radiobacter from infected vines. Ophel and his coworkcrs showed that hot water treatment (50°C for 30 minutes) of dormant grapevine cuttings decreased the inocula level in infected cuttings and can produce crown gall incidence in a nursery. However, complete eradication of the pathogen could not be achieved by hot water treatment. In areas where freeze injury is not common, the incidence of the disease may not be a concern. This apparently is the situation in Ethiopia and other tropical countries.

Virus and virus- like diseases Viruses spread to healthy plants through propagation chain, i.e., through rooted cuttings, layers, buds and grafts, and generally by insects. Insects and nematodes are proved vectors for spreading virus; but sap is generally reported not important for spreading viruses in grapevines (Fic and Vanek, 1970). Viruses and virus-like diseases of grapevines have one feature in common: they are transmissible by grafting infected wood to a healthy plant during propagation (Goheen, 1970). Thus, transmissibility by budding, grafting and rooted cuttings once ubiquitous, still is an important feature of viruses found in grapevines. The important viruses and virus-like diseases found in different grapes growing countries are fan leaf degeneration, leaf roll, and corky bark.

FanleaS degeneration Fanlcaf degeneration is the oldest known virus disease of Vitis vinifera. The name is derived from the peculiar malformation of infected leaves. The disease is known to occur worldwide. It is often callcd fanlcaf, but the correct name is fanleaf degeneration (Martenlli and A vino, 1988). The actual impact of the disease varies with the tolerance of the cultivars to the virus. Cultivars tolerant to the disease produce fairly good crops while those sensitive to the disease arc severely affected, showing progressive decline n yield and quality of fruits, shortened productive life of the vineyard, reduced rooting ability of propagation material, and decreased resistance to adverse climatic conditions Hewitt, 1962). Sap inoculation, but not through vine seeds transmits the grapevine fan eaf virus.

Symptoms: three distinct syndromes evoked by different reactions to the casual agent hat characterize the disease (Hewitt, 1950). The common symptoms includc, nfectious malformation, severely distorted leaves, malformed shoots showing abnormal branching, double nodes, short intemodes, smaller and fewer bunches than normal, ripening irregularly with shot berries and poor fruit set are frequently observed.

[99] Asfaw Zelleke

Control: several lines of action can be pursued for controlling fanleaf degeneration, some of which include control of nematode vectors, cross protection, breeding for resistance, and selection and production of virus-Tee stocks (Raski et al., 1983).

Leafroll Vhe disease, which is found wherever the grapev ine is cultivated, is characterized by rolling downward of the leaf margin (Gohcen. 1988). It causes chronic damage and onsiderable yield loss in vineyards where the disease has established. It is spread in ropagation by the use of infectcd wood albeit there is evidence of the natural spread Sn Europe (Hewitt, 1988).

Symptoms: According to Hewitt (1988) all narts of the infected plant (leaves, shoots, canes, trunks and root system), are slightly smaller as compared to that of healthy one. It delays fruit ripening. Clusters are smaller than normal. Leafroll and K deficicncy are somewhat similar except in the leafroll the early rolling of the leaves takes place in the ’nasal leaves whereas in K deficicncy the leaves along the middle length of the shoot are the first to show the symptoms.

Control: propagation from healthy mother vines is the best means to control the disease. Further, the need for the establishment of sound quarantine system, using clean farm tools, destroying suspected plants or plant parts arc unequivocal.

Corky bark Corky bark is found in all regions where the grapevine is grown. It is a virus like disease but no virus has been isolated and proved to be its cause (Hewitt, 1988).

Symptoms: Affectcd leaves resemble those of leafroll but are more severe; they become smaller and pale and roll downward, low in vine vigor and in productivity (Beckman and Goheen, 1970).

Control: use of propagation stock obtained I'rom disease-free mother vines. In general, the best control methods for all virus diseases is the use of clcan, virus-free planting material and an effective certification and propagation system.

Insect Pests and their Control Ii most areas where the grapevine is growing, several types of insect-pests and nematodes are known to attack the grapevine and its fruits. Damages caused by insects arc variable usually ranging from no-damage to scrious-damage (Winkler et al., 1974). No common insect-pest attacks all parts of the grapevine. Insects such as scalc insects, bunch and twig borer attack arms, canc and trunks; while grape folder, grape hopper, grasshopper, omnivorous leaf roller and mites attack the leaves. However, it is

[100] The Grapevine unlikely that most of these insect-pests are equally distributed in all areas where the grapevine is growing. The presence of predators (natural enemies of the pests) seems to influence the population of the insects in many grape-growing regions of the world. In general, the above ground parts of grapevines are subject to attack by a wide range of insects. These are mites, termites, beetles, caterpillar, grasshopper, and scales, aphids and lcafhoppers. The relative importance of these pests in affecting different parts of the grapevines (leaves, stems, flowers and fruits) varies greatly among grapevine growing countries. The importance of these pests in different grape growing areas within Ethiopia also differs. Termites, honeybees (starting at the stage of full maturity honeybees tend to invade berries/clusters and suck-out sugars/nectars) and caterpillars arc the most predominating ones (personal observation).

Grape Leaf roller (GLR) The lcafhoppcr are most common vineyard pest. It may not however, be treated because vines can tolerate fairly high populations without significant harm (Jensc and Flaherty, 1988)

Injury: The adults and nymphs feed on leaves by puncturing the leaf and sucking out the sap/contents. The leaves lose their green color, dry up and fall off the vine thus reducing effective leaf surface and photosvnthatcs activities.

Control: A number of parasites are known as effective biological control for grape leafroller. The most commonly observed parasite of the grape leafroller is the larval parasite, wasp (Bracon cushmani). The use of insecticide has been found effective if applied properly on time. Dipcl. Thuricide and Biotrol XK perform best when applied ihrcc to four days before the leaf rolling activity commences, according to Jensen and :laherty.

Thrips Thrips arc of great concern to growers becausc they injure clusters, new shoot growth, bliagcs. It is of a recent incidencc observed in some vineyards of Merti Jeju attacking clusters and shoots/foliage. The species has not yet been identified but most probably it could be European grape thrips (Drepanothrips reuteri), which is mainly responsible for foliage damage and fruit scarring and shoot stunting. However, the economic damage of thrips on wine grape varieties due to very severe scar on fruits, might be considered as minor problem when compared to the damages caused on tabic grapes as appearance has significant impact on market v alues of the final product of the latter.

Symptoms: Most the affected leaves appear smaller with bronze color; shoots arc distorted and stunted, they do not grow to normal size. Shoots tend to recover in warmer weather, internodes are shortened and scarrcd; injure fruits at early stage when

[101] Asfaw Zelleke the berries arc about 3 mm in diameter, berries become scarred, deformed and crookcd (personal observation at Merti Jeju Farm).

Control: sulfur dusting and spraying with chemicals (dimethoate/Cygon and 0.1 % malathion) are found effective when applied at the proper time (Amsalu B., Merti Jeju Agro Industry Enterprise, personal communication).

Cutworm Cutworms, which are the larvae of moths attack many cultivated plants. They are Dresent in all tropical areas. They feed on the buds and cause severe damage. They are one of the most injurious pests of many crops worldwide. On grapes, larvae are the most destructive stage.

They feed on developing buds. In the daytime both, the larvae as well as flying moths hide and emerge to feed after dark (Joos and Dibble. 1981). injury: Cutworms feed on all kinds of vegetation (cereals, ornamentals, trees, grapes etc.). The injury on grapevines is most serious between the times buds begin to swell to when shoots are several centimeters long.

Control: The use of properly selected chemicals can prevent major losses in grapes. A carbaryl (Scvin) spray, which is easier to apply, and more effective can be adopted in the early growth stages following the company’s recommendation. Natural enemies provide the most suitable approach to the management of insect on grapes. It would be difficult to grow grapes economically in the absence of the natural enemies. The use of integrated pest management (IPM) strategies provides effective results. IPM is a set of standard procedure that growers seek to combine the best of various control measures including biological ones. A well-organized pest management program offers maximum results at lower cost and with a minimum of environmental disruption.

Fruit Flies The fruit flies also called drosophila feed and reproduces in fruit dumps, culled fruits and vegetables left in field or vineyard (Stombler, 1960). They also feed on the berries through fresh crakcs in the skin. Crakes arc formed because of rapid berry enlargement during ripening or irrigation during acute moisture stress. They multiply rapidly depending on the weather. Moreover, there is always a large population present to attack the grapes at maturity. In general, fruit flics may become a problem when grapes approach the ripening stagc(Jenkins, 1967). It is difficult to control the fruit flies because of their feeding, breeding and migration habits. Destruction of breeding places and safe disposal of infested fruits and vegetables, fresh fruit dumps etc, are the best means of controlling the pest. They can also be treated with systematic insecticides (as per the agent’s recommendation) and bait sprays of maldison and protein hydrolysate and /or release of sterile male fruit flies arc used in conjunction with the quarantine measure to restrict the distribution of the pest (Myburgh, 1961).

[102] The Grapevine

Termites Termites are social insects and six different castes of the termite are known. These nclude the prealatcs, alates, primary queen, supplementary queen, worker and soldiers. Bach cast, has its own distinct role to play. Termites cat away the xylem/heartwood and leave gaps in the heartwood core. They avoid the living sapwood. Usually, the entire core of the wood is honeycombed, and its structural strength is weakened leading to breakage with least strain.

Control: prevention is the primary means of control. Care should be taken to avoid mechanical injuries of the vines with cultivating tools. Use stakes that are resistant to termites (cedar). Use chemicals in consultation with local chemical dealers. Chloropvriphan (2 g per liter of water) has been found effective. A vine replacement program such as layering should be initiated in older vineyards.

Phylloxera The roots of grapevines are also subject to a few pests, which are of great importance in many countries where grapevines are of commercial importance albeit it has not been found as serious pest in Ethiopa. The most important of the root pests are phylloxera (Daktulosphairct vitifolia) - root-louscs, which feed on roots and leaves of grapevines. It is a scourge of viticulture. The life cycle of phylloxera is complex (Coombc. 1963; William and Granett. 1988). It has a root-feeding phase (radicicole), and a leaf-feeding phase (gallicicole). The root form may be found in soil at any depth where grapevine roots arc found. Soil that has high clay content and cracks when it dries is a better medium for the pest than soil with high sand content, which docs not crack. Vines planted in sandy soil are not affectcd by phyloxera. The foliar feeding orm of phylloxera is frequently found on the foliage of susceptible cultivars in humid viticulture regions. Leaf galls are rarely observed in the dry areas. Phylloxera has sucking mouth parts and they produce characteristic lesion on the roots of grapevines mown as nodosites and tubcrosites. Regeneration of new roots is inhibited. Water and mineral uptake by roots is greatly impaired. Affected vines becomc weak and eventually die. Roots of Vitis vinifera are susceptible while the leaves arc resistant to phylloxera (King and Buchman. 1986).

Control The use of resistant rootstock and quarantine are the best controlling means of phlloxera. The recommended cultivars arc listed in the rootstock scction of Chapter IX.

Nematodes The second important soil pest of grapevines is nematodes. Nematodes arc the highly damaging pests of grapevine roots. Nematodes do not cause specific symptoms on aboveground parts of the grapevines. The root knot nematode ((Meloidogyne), citrus nematode (Tylenchulus) and dagger nematodes (Xiphinema index) are the most important group that inflict heavy damages during feeding. They reduce grapevine vigor and production. With all spccies of parasitic nematodes injury to the root system

[103] Asfaw Zelleke through feeding results in reduced production of new roots and uptake of water and minerals.

Root-Knot Nematode Root-knot nematode is the most widely distributed pest of grapes that seldom kills grapevines; more often plants decline in vigor and become more susceptible to stress (Winkler el al., 1974). The rate of development varies with temperature between 12° and 30°C that they arc less active in cool weather and hence damage is less sever in cooler regions than in wanner regions. They spread into new areas by the movement of infested footings, infested soils and cultivation implements or irrigation water and flood. The root knot nematode males do not feed and arc not of dircct concern to grape growers while the female nematodes when mature into egg laying adults, cause a cellular changc in their feeding site in the plant (McKenry, 1981). This change results n the formation of “knot" or “gall" seen on the root surface. Root knot nematode is best adapted to coarse-texturcd soils (sand loamy sand and loamy sand).

S ym p to m s: Abnormal cell growth occur causing swelling or enlargement of the whole root. Root function is disrupted and vine growth is reduced due to poorly iimctioning of roots. Small swellings or galls arc produced on young feeder roots or secondary rootlets followed by death of feeder roots.

Citrus nematodes The citrus nematode (Tylenchulus semipenetrans Cobb) is considered as one of the most pathogenic nematode species on grape (Raski, 1988). It is now known to be worldwide in distribution on the grapevine. Vine vigor is remarkably reduced; affected plants do not have resistance to withstand stressful conditions. Yields gradually decline and vineyards becomc uneconomical.

Slymptoms: death of feeder roots; no visible necrotic spots or malformation produced; producc a profuse, gelatinous matrix to which soil particles cling, giving the vines dirty appearance.

Dagger nematodes The dagger nematode (Xiphinema americanum is generally known for its large size aid lengthy root penetrating spear that allows it to feed deep in root tissue (McKcney, 1 288). It is present in all the major grapevine-growing areas of the world. It is the most thoroughly documented and is a devastating pest of grapes (Raski et al., 1965; Raski, 1988). Affected vines decline considerably, producing fewer shoots and ultimately vines become very unproductive. Xiphinema americanum is also a vector of grapevine fen-leaf virus. Infestations of viruliferous X. americanum have even more devastating effects on vineyards and hence affecting its economic values.

Symptoms: affected vines exhibit many dead feeder roots, which results in a kind of "witches broom" effect (Lear and Lidcr, 1959; Raski et a l 1988). Most feeding takes placc near root tips and root growth stops soon after feeding begins. Darkened,

[104] The Grapevine necrotic spots spread over the entire root tip are observed as result of multiple prolonged attacks.

Control: The control method mentioned could be applicable to control all the nematodes mentioned here. Nematode control methods involve keeping them away from fields not yet infested through reducing the nematode population using tolerant rootstock materials or in the soil before planting. Treat soils with nematocides before planting. These chemicals are highly poisonous and great carc must be taken, while using them. For treatment before planting, 1,3-dichioropropene or methyl bromide is recommended. However, effective methods of controlling all pests of the grapevine arc not yet available. Combination of two or more chemicals, biological and cultural methods can control some of the pests successfully. Most effective controlling methods of all the nematodes (Raski, 1988) are given below: L sc of resistant/tolerant rooistocks

• Side dressing of established vineyards with 1,2 dibromo-3-chloropropane fumigant (DBCP) • Excluding new infestation ® Establishment of constrictive quarantine system • Use of hot water treaunent ( few minutes) for washing rooting thoroughly

In many grapevine-growing countries, the use of cultural, mechanical, biological and chemical methods are integrated to control pests. Under Ethiopian conditions, this has to be established and evaluated at each agro-ecological zone. For a future research program on grapes, priority should be given to work out proper integrated pest management program applicable for the local conditions. This has to involve the preservation of beneficial predators and parasites through use of the least harsh pesticides; use of fewer chemical applications per season wherever feasible; proper timing of treatments; and preferred use of cultural methods of control. Some of the insecticides on the market are very hazardous to spray and should be avoided where users are not trained in their proper use. Inexperienced growers should only use those pesticides that arc available, safe to use and still effective. Since there is very limited information with regard to kinds of pests occurring on grapevines in Ethiopia, the list of pests mentioned in here may not correspond to the actual pest scenario prevails. It has to be stressed here that observations and investigations on pest development and types of pests occurring in vineyards of Ethiopia should be given priority in establishing a systematic research program for grapes. It is worth mentioning that in areas where soil bom diseases and other unsuitable soil conditions prevail, the appropriate rootstocks (see Chapter IX) could be used to control them effectively.

Vertebrate pests Mammals such as antelopes, rabbit, and mole rats/gophers are major problems in all vineyards of Ethiopia. The extent of the problem can be determined by the location of the vineyards. Vineyards that are close to dense tree/bush are prone to damages by these mammals. Several factors must be considered to control them successfully. Most of these are:

[105] Asfaw Zelleke

• spccies identification; • suitability of the area to habitat/house them: and • availability of appropriate methods and efficient monitoring system to control them. These mammals are usually controlled physically by individuals or using treated baits, traps and other available materials.

Mole rats/gophers Mole rats arc stout and short-legged animals measuring of about 18 cm. They live underground in a burrow system. Either the system is constructed in main tunnels or side tunnels fashion to push out dirt. Mole rats are most troublesome throughout the year. They cause serious vine damages and loss to vineyards. The burrows also divert irrigation water thus causing damage to irrigation and other cultural operations. They feed on succulent underground parts of plants. They damage vines by cutting roots. They remove the bark tissues of roots below the soil line, in a short time with substantial loss to vineyards. They have the capability to pull the entire young plants under ground and some time graze on plants above ground near the burrow opening. The extent of above ground damages that ultimately cause death of vines is usually Dbserved in most vineyards of Ethiopia.

Control: There is no effective and reliable control method of mole rats because of :heir underground habitation. However, the most common methods are mentioned.

Vfonitoring: significant vineyard damage can result from mole rat (gopher) nfestation. Monitoring of occasional infestation is important as population build up can be detected by an increased number of mounds and appropriate control measures can be exercised.

-Proper management: mole rats can be controlled effectively from vineyards by using poison baits. This is the most widely used method. It can be applied by hand or mechanically. Toxic grain baits such as strychnine (0.2 - 0.5%) can be placed in the burrow system following manufacturers’ instructions. Zinc phosphate (RATOL™ ) is a registered chemical in Ethiopia to control rodents. In large commercial vineyards, where the problem is serious, mechanical baiting is more efficient, effective and economical (William et al., 1982).

Trapping: metallic hook trap with different attractants (aromatic plants) and food baits or .special traps should be used to control mole rats in small vineyards. Such traps can be prepared locally. l^ooding: in areas where grapevines are growing by supplemental irrigation, vineyards are flooded so that mole rats may be drow'ned or forced out to the surface where they are susceptible to natural and human predation.

[106] The Grapevine

Babbits Young vines are susceptible to damages by rabbits. A routine tour through the vineyard looking for rabbits will assist growers to tacklc the potential problem and develop appropriate control measures.

Control: Uses of natural enemies such as shooting, and hunting dogs are effective means of controlling rabbits. Physical means of controlling are mentioned below.

Fencing: the use of rabbit-proof fencc is the best control. A fence (one meter high) of barbed wire or poultry netting (mesh-wire) makes an effective rabbit-proof fence.

Vine guard: individual vine guards provide effective protection. Cylinder of mcsh- wirc may also provide better protection from debarking.

Monitoring: systematic monitoring/patrolling might effectively reduce the rabbit population and reduce damage in vineyards.

Poisoning: the use of toxic materials (baits) could be economically feasible to control large number of rabbits over large area involved.

Antelopes Antelopes arc a potential threat to vineyards that are located close to wooded or brush areas where they usually seek shelter. They damage vines by stripping off the foliage and eating away the tips, the tender parts of the shoot. Sever stunting of vines may result from repetitive antelope browsing.

Control: Different control mechanisms are available but the most common ones are discussed here.

Fencing: the most effective method of excluding antelopes from a vineyard is fencing. It is advisable to locate vineyards far away from wooded or brush areas, which provide shelter for antelopes or construct fences at least along the side of the vineyard adjacent to uncultivated land (wooded area) where antelopes may be found. Checking vines periodically is essential, as fences age they become vulnerable to breakage.

Habitat management: grapevines are favored food for antelopes especially when new foliage is developing. Eliminating habitat/shelter is an effective means to control antelope provided area coverage and density of woodland/shrub land is manageable. .

Birds 3irds are common pests in all vineyards. They cause substantial damage to fruits especially when they begin to ripen and change color. Early detection will increase management success. Clean cultural practices will reduce bird problems. Several factors must be considered to control birds. These include two major categories of control mechanisms, viz. physical and mechanical:

[107] Asfaw Zelleke

Physical means:- • Identification of species and apply effective management techniques, • Changing the habitat of birds by rcmo\ ing trees that harbor birds’ nests so that the site becomes less attractive to them, • Adjusting management program and. • Applying continuous monitoring scheme Mechanical means;- Trapping: sites where birds enter the vineyard and where the trap is visible to the bird are the best trapping areas. Traps should be properly placed and baited to catch birds effectively and efficiently.

Baits: rape and canary seeds treated with poisonous chemical (strychnine) have been found effective. Chemical treated and untreated baits usually placed above the vines will producc best results and should continue until economic damage ceases.

Chasing: chasers are usually assigned to drive birds away using pieces of stones and the like.

Nets: vines are covered with nets to keep birds away from ripening berries and hence preventing damages caused by birds on small acreage only. It is neither economical nor practical to apply this method on large acreages. disorders Caused by Chimeras Chimeras are new genotypes resulting from mutations occurring in meristcms (Rives, 1970; Goheen, 1988). Chimera is also called bud sports that may appear within population of grapevine cultivars. They are usually stable and can be propagated asexually just like any other perennial plant genotype. They are occasionally selected as new' cultivars with a new description. Though they can be propagated asexually, they do produce infections when they are grafted onto healthy plants. Thus, the fact tnat no transmissible agent is present in chimeric vines distinguishes them from virus- hfected vines, which they may resemble. Chimeras are found wherever grapevines are grown commercially. Four chimeras arc recognized occurring in grapevines, according to Goheen. They are:

Variegation: this is a common chimera where a mosaic pattern spreads into new tissue and organs that develop from the point of mutation. A spot within a leaf, a fruit cluster, a single shoot, a major part of the vine, or entire vine may show the mosaic pattern. If a variegated cane is asexually propagated, the chimera persists in the daughter vines.

Fasciations: this is another common chimera in grapevines. The shoots, petioles or cluster pedicels develop into a flattened shoot rather than the normal round ones. This can appear on any part of the vine. Fasciations occur frequently on some cultivars, for example Petit Syrah than others.

[108] The Grapevine

Witches broom: this is less common in the grapevines than the above two types. Buds developed from original mutation seem to grow a shoot tissue after they are initiated and develop into a bushy growth, covering part of the vines. Shoots that develop in the broomed tissue do not mature and no fruit cluster develops on such shoots. Leaves are smaller and remain green longer than normal leaves. Cuttings made from dormant affected cancs can be grafted to a normal rootstock, they continue to develop as a "Witches broom", but the rootstock does not become affected.

Distorted growth of leaves: this is caused by unnamed chimera. A name has not been given to this type (Goheen, 1988). One of the two outer layers in a bud meristem mutates, which results in a mix of normal and affected tissue within developing shoots. The shoot grows normally but leaves are grossly misshapen and are smaller than normal leaves. Sinuses of the leaf blade are reduced; the color of the blade indicates that some chlorophyll-bearing tissues do not develop. Cuttings made from affected canes root and produce vines with distorted leaves with no commercial fruit production. Buds from affected cancs when grafted onto healthy plants grow out as affected shoot but do not transmit any agent to healthy plant.

Control Chimeras observed on young vines in a new vineyard should be removed by pruning back to normal tissue. However, this does not eliminate fasciations, as these mutations perhaps seem to result from mutatable genes where, the rate of mutation cannot be controlled.

Nutritional Disorders Nutritional disorders in the grapevines are manifested by changcs in the growth of the vines. Changcs in the shape, color, chemical composition and performance area arc observed in response to the disorder. Such visible symptoms provide clues about their cause, which could be due to either deficiency or excesses of one or more nutrients. Soil and petiole analysis usually confirm nutrient balance.

[109] Asfaw Zelleke Chapter VIII

Categories of Grapes

ommercially, grapes may be classified into five main categories depending upon Ctheir purposes (Pandy and Pandy, 1996; Jindal, 1999): (i) Table grapes, (ii) Raisin grapes, (iii) Wine grapes, (iv) Juice grapes, and (v) Canning grapes. There is specific variety most suited for each purpose, and certain varieties qualify for more han one purpose. The grapes arc also used for the preparation of vinegar and winery by-products, which have significant uses.

n Ethiopia, however the three major /categories/classes of grapes according to the purpose of intended use include wine, fresh-tables and raisin grapes. The category of grapes to be grown is largely decided by environmental factors, market-demand and availability of facilities. In situations where the respective grape varieties are not available, any grape variety can be fermented into wine, or can be eaten fresh, or dried into raisin with special oil treatment to avoid sticking albeit the acceptable quality may not be attainable. It is advisable and economical to use the right type of grape varieties for the specific purpose.

Wine Grapes

The wine grape varieties are capable of producing quality wines. There are two kinds o f wines, viz table and dessert wines. Wines made from grapes of high acidity and moderate sugar content are classified as table (dry) wines; whereas dessert wines (sweet) arc made from grapes of high sugar content and moderate to low in acidity. The sugar:acid ratio in grapes is the function mainly of temperature effects. Therefore, the best vines for wine grapes are grown in cooler areas while the dessert-w'ine grapes arc grown in warmer areas. Unlike other fruits, the grape berry has high content of fermentable sugars, relatively high N-content and the natural association of fermenting yeast. The grape variety and its management aspects in the vineyard can also affect the quality of the wine besides the fermentation technique, the processing and aging of the wines. Many distinctive wines such as (Chenin blanc and Pinot noir,) require specific grape varieties. Many varieties are inherently of poor quality for some wine types w hile some varieties can be converted into good or standard qualities of several wine types. Two aspects are necessary to make wine. These are the grape fruit from the g-apcvine and yeast for fermentation. The grape is a seed-bearing member of the plant k ngdom. while the yeast is a member of the thallophyte. The genus Saccaromyces (sugar fungus) that includes the yeast is the most significant in all forms of commercial production of alcohol from sugar. The variety of yeast (.S', cerevisicie var. ellipsoidui) is well adapted to fermenting grapes to wine production and is often found on the skin of the ripe wine grapes in sufficient amount to make possible the fermentation of the

[110] The Grapevine crushed grape without any additional inoculation. Another type of microorganism found on the skin of the grape berry is the wild yeast, which is often much more numerous on grapes than arc the wine yeast. Crushed grapes or grape juice ready to be fermented is commonly called "must". Fermentation is therefore the conversion of sugar (glucose) to alcohol (ethanol) under an aerobic condition in the presence of certain enzymes. The grape berry contains sugars, acids, pigments, tannins and odorous compounds. Some of the ingredients, particularly sugar and amino acids derivatives arc transformed by yeast during fermentation.

Classification of wines

Wines can be classified based on origin, color and the amount of carbon dioxide they contain, the sugar contcnt and many other chcmical charactcrs (Singleton, 1975). In the developed countries, actual commercial sale of wines is generally made according to country and district of origin. Climatic conditions, varieties used, winemaking procedures and custom usually make the wines of different viticulture regions different from one another. Grapes have been harvested and made into wine for over several centuries. Wine quality was unequivocally extremely variable in early times. It has been greatly improved by empirical development and research work. This section therefore discusses issues related to understanding the process of grape berry development and ripening, and practicing proper harvesting and handling operations.

The physiology and biochemical nature of berry development ^he physiology and chcmical aspects of berry development arc well discussed in Chapter-I. In here, some very relevant factors that are specific to wine grapes are mentioned in brief. These arc:

Compositional changes during ripening Sugar accumulation commences at verasion. The stage of development when berries begin to soften, increase in sugar: acid ratio and change in color of pigmented varieties is referred to as verasion. At this stage of development, berries begin to soften, increase in TSS:TA ratio and change in color of pigmented cultivars. The concentration of sugars increases steadily during ripening but the rate of increase is :nfluenced by water supply to the vines (Winkler et a l, 1974). Low water stress favors acceleration of sugar accumulation while rain or irrigation decelerates it or even causcs a temporary reduction. Malatc decreases with ripening due to respiration, while K ncreases. Flavor volatiles and some amino acids accumulate later during ripening while sugar increase recedes.

Maturity indices for wine grapes in wine grapes, the choice of harvesting/picking date has important influence on wine quality. The time of harvesting is usually determined by the availability of labor, the weather, discases/pcsts incidence and the stage of ripeness since a grape is a non- climactcric fruit. Wine quality depends on the chemical compositional changes as the berries ripen. It is therefore important that the wine grapes reached the stage of

[111] Asfaw Zelleke development where the relation of the different components of the fruit, i.e., sugar, pH, acid and especially, TSS (°Brix): acid ratio is optimal for the production of quality wine of desirable type. Some of the important maturity indices that play significant role in maximizing quality of wine are discussed here.

Total soluble solids (TSS) TSS is the most important index of ripeness. The TSS content determines the quality of the wine. The higher, the TSS, the higher would be the potential alcohol of wine. The normal range of TSS is from 18-24 %, which yields 10-13.5% alcohol. Most yeast types cannot survive at alcohol levels greater than 14 % (Singleton, 1975). Overripe nerries with TSS values of 30 % are often used for making sweet table wines.

Acids: Acids give crispness, brightness and thirst-quenching qualities to wines and are essential components of balance in a fine wine. Most of the acids are tartaric and some are malic and succinic acids. The grape acids protect the 'must' from the growth of spoilage causing organisms. The acid and pH have important effects on fermentation, according to Singleton. Acidity makes an important contribution to wine palatability. Low acid wine is flat while a high acid wine is sharp and indigestible. Titratable acidity often ranges from 6 to 10 g per liter in wines of most developed countries. Higher values may occur from wines of cooler areas or green grapes while lower values could occur in grapes from hot areas.

{Sugar: acid ratio: Sugar and acid are the important bases for identifying the right stages of ripeness in grapes. It is useful for the purpose to combine the values of these two into one value. Sugars-acid ratio is the most appropriate index, since the ratio increases sharply as berries ripen showed that the Brix: acid ratio or sugar: acid ratio serves as an accurate indication of maturity and can be used to predict the potential wine quality of grapes (Berg 1960). The specific ratio may be readily estimated by extrapolation from a sequence of measurements made as harvest approaches. It is important to understand that these values vary with wine type and need to be specified by the wineries.

Color, aroma and flavor of wine

Wine color: red or colored wine grapes contain natural pigments (anthocyanins), which are responsible for the color of wines (Kliewer and Tones, 1972). In all red wine grapes, these pigments are located in the skin; the pulp is essentially colorless. The alcohol produced in the early stage of fermentation dissolves the pigment and liberate it into the wine. Generally, in pigmented varieties, the quality scores of wine correlates directly with ionized anthocyanin concentration.

/>j*oina: a pronounced odor or fragrance present in grape juice due to the presence of certain aromatic substances (Webb and Muller. 1972). The level of monoterpines and glycosides (glucosyl-glucose) are also used as maturity indices.

[112] The Grapevine

Flavor: it is a distinctive quality parameter regarding taste or smell of wine, according to Webb and Muller.

C rape sampling and testing It must be evident that vineyard sampling has to be considered for variation in the berry population to be tested and apply a standard method of sampling. Vineyard variation docs exist between: vines, bunches that arc exposed/protectcd, inside/outside of the bunches, shoulder/tail, berries located on top/middle/bottom of the bunches, large/medium/small sized berries, and early/late maturing types (Jordan and Grosser, 1984). An optimal sampling plan includes an assessment of the v ariation within each component of vine variety. According to Jordan and Crosser, sampling methods used in developed countries include:

• Whole vine -all fruits arc taken from cach selected vine, ® Bunch- the whole bunch is taken; • Sprig- a segment of the bunch stem with attached berries is taken; • Bern - individual berries arc selected from eacli sclectcd bunch.

The choice of sampling method is affected by the size of the sample for processing; soecd for collecting samples; relationships on results of samples collected at different times and accuracy required for the sample. Bunch and berry sampling arc the main methods used in most vineyards. Whole vine sampling presents a problem in the ability to select representative samples. Recommended sampling of vines every tenth vine in every tenth row taking 10 berries per vine using two randomly selected bunches, with 5 berries from the inside of one and 5 from the outside of the other (Rankine et al 1962). The berries taken comprise 2 from the top, 2 from middle and 1 from the bottom of the bunch. It is advisable to take samples at the same time of the day preferably in the morning when berries are free of dews which otherwise may affect the results. Fruits should be stored in sealed polythene bags at 2-4(,C and should be pressed within 24 hours.

Harvesting wine grapes

Hand harvesting The most common harvesting practice of wine grapes is done manually by hand. Each bunch must be loeated and held and the bunch attachment is snapped or cut. The characteristic of the variety influences the rate of harvest. Few varieties have bunch stems, which easily break. However, this method may damage the fruit and cutting of each bunch stem is necessary. Berries of some varieties shatter readily when being liarvested and extra care is required to reduce losses. Apart from these variety factors, he rate of hand harvest is determined by the method by which the vines are pruned; he crop load; bunch size: trellis type; canopy density and shape; and condition for picking including temperature, humidity, ground condition and access.

Usually, pickcrs use ordinary pruning shears in most developing countries (e.g. Ethiopia). Small pairs of secatcurs or grape picking snips (with long narrow blade) are

[113] Asfaw Zelleke used in developed countries. Well-organized picking teams can enhance the speed of the harvest. A good team usually has a leader, pickers and transporters. The leader is in charge of the operation and controls harvesting of immature berries in particular. A good picker may harvest from 200-1600 kg per 8 hours day work. The method of payment for pickcrs varies according to the range of factors that influence cost of harvest. Payment on time basis is expensive, if pickcrs arc unskilled or unmotivated. Contract picking enhances a fixed cost per volume of weight of fruit harvested. This may either be at a piecework rate per unit of fruit picked (basket) or by team sharing a 'ate per 10 0 kg (quintal).

Machine harvesting Harvesting by machine is an established part of viticulture in most developed countries. A number of factors influence the success of mechanical harvesting. From the outset, for mechanical harvesting a vineyard needs row and head land width that is sufficient for passing and turning the machine. Marking and numbering of rows and ihe stage of ripening of berries also have strong influence on the success of machine harvesting.

Post-harvest operations of wine grapes

Proper handling Minimal handling of grapes after harvest reduces damage caused by juicing and breakdown. The type and degree of movement of the container and the duration of the handling directly affects the extent of damage (May, 1977). The breakdown process of oxidation and enzymatic activity and the activity of wild yeasts arc directly related to the length of time between harvesting and processing including the holding temperature. Harvesting during the coolest part of the day, together with rapid pre­ cooling of the grapes minimizes this damage and extends post-harvest life.

Protective chemicals Using compounds that form sulfur protects wine grapes by antiseptic action on yeasts and bactcria, its anti-oxidant effect and by enzyme inhibition. SO: may be formed by the addition of sulfurous acid—pressurized and in liquid form—as a freshly prepared S 0 2 solution at a lower concentration, or as mctabisulfite salts, which yield about half their weight as S0 2 (Hamilton and Coombe, 1984). They suggested potassium metabisulfite (PMS) as the recommended salt. The salts may be applied in solution form or as a powder. The latter offers the advantage of both ease of addition as well as being more stable than a low concentration liquid; but it should be fresh as it also breaks down in storage. According to Hamilton and Coombe the administration and dosage needs adjustment to obtain SO; concentration that is appropriate for the type of wine to be made and to avoid excessive amounts that may result in bound sulfur compounds. Ascorbic acid (antioxidant 300) or its isomer erythorbic acid (antioxidant 310), can be used to augment the anti-oxidant properties of S02. The displacement of air with denser, chemically inactive gases such as nitrogen and carbon dioxide effectively reduces non-enzymic oxidation .

[114] The Grapevine

Table Grapes

The grapes that are used either for fresh consumption or for decorative purpose arc designated as table grapes. The tabic grapes should have attractive appearance, good eating and shipping quality. The berries should be large, uniform in size, shape and colour. Grapes with Muscat flavour, thin skin, firm flesh, and seedless arc preferred, e.g., Thompson Seedless, Perlettc, Muscat of Hamburg etc.

In the developed countries, it is a specialized area of viticulture for domestic and export markets. It thus has gained prominence as one of the leading fruit exports in the USA, Europe, Australia and South Africa (Nelson. 1979). Tabic grapes arc somewhat different from grapes for making wines and raisins. In the latter two types, grapes arc not consumed fresh. They must be processed in the form of wines and dried grapes (raisins). Hencc, table grapes must be attractive to the eye and tasty the palate. Uniformity in shape, size, color and evenness in maturity arc important characteristics of the fruit. Distribution of berries on the bunch in addition to uniformity in shape and size, attractive appearance of fruit at harvest, free of berries from wind damages, spray residues, insect infestations or fungal disorders are equally important factors that affect quality of fruits. Other factors that affect quality or sale of table grapes includc eating quality, which are judged by ripeness, flavor and texture of the berry and absence or presence of seeds. The presence of seeds is associated with the size of the berries. Large sized berries are usually seeded. The small sized seedless grapes arc sprayed with growth regulators (gibbcrcllic acid) to increase the size (Weaver, 1972). The shelf-life and suitability for handling and transport arc equally important factors affecting quality of fruits. The texture of the berries is a prominent component of eating quality and is important for handling, transport, storage and shelf life of the jrapes. Varieties vary in flavour. The variation is primarily due to seasonal conditions, soil types and irrigation practice. Limiting irrigation prior to bloom can intensify the flavour of cultivars. In general, table grapes have very distinct characteristics and the most prominent ones are secdlessncss, attractiveness and the sugar level (17-19 °Brix).

The culture of table grapes

S o il Even though grapes arc adapted to a wide range of soil types, table grapes in general have preferences for soil types. Deep sand or gravel soils arc suitable for early cultivars like Pcrlette, Cardinal, while very late varieties (Dodema Alcitico, Grcnache noir, Kai Dubie,.. etc.) preferred alluvial soils. Table grapes with excellent flavor and keeping quality are produced on slightly less fertile soil that favors extensive root development (Cirami et a/., 1986). Vines on very rich, fertile soil usually have excessive vigor that requires careful management to avoid production of poorly colored fruits.

[115] Asfaw Zelleke

:How direction and spacing The direction of prevailing wind dictates the orientation of rows as discussed in Chapter IV. The orientation of the rows will have the advantage if it is at right angle to open up the vines on one side so that color development and early ripening are promoted. Correct orientation and proper trellising minimize problems such as surface drainage and irrigation, poor color development, sun burn ...etc.. The usual spacing between vines is 2.5 by 3.5 m, which provides ample room for vine growth and vineyard operations. Spacing within the row is generally wider for table grapes than for wine grapes. Wider spacing promotes the development of a larger vine framework. Less vigorous varieties are planted closer (1.5 by 2 .0 m).

Trellising In table grapes the trellis for a particular site arc related to the cultivars, spacing and vigor of vines. Trellising system is intimately linked to the quality and productivity of table grapes. The trellis system in table grapes permits:

• Even distribution of foliage to allow adequate light penetration to the basal buds to improve bud fruitfulness and also to improve ventilation to facilitate control of insect and diseases: • Pollination and fruit setting and pigment development in colored cultivars; • Bunches to hang free of foliage, canes or cordon and prov ides convenient position for harvesting; and • Protection against sun burn

In general, vines that have high yield capacity. demand larger trellis as compared to those of lower capacity albeit the demand for water may be too excessive for those vines on larger trellis. If the trellis system is too small, bud fruitfulness, fruit ripening and development of color may be affected (May and Antcliff, 1969). Different trellising systems are used in the developed countries. In the selection of trellis systems, the best designs that arc economically feasible and provide simple vine management strategies for high productiv ity of quality grape production should be considered.

Nutrition The level of nutrition needed by the table grapes is higher than that needed by wine grapes. Table grapes require frequent guidance from standard tissue analysis. Larger application of nitrogen is used on low vigor vines. However, some studies show ed that high N-levels could reducc fruit color and soluble solids in some varieties such as Emperor (Winkler et al., 1974). K is applied to pigmented varieties (red or black) with the belief that it will improve coloring while phosphorus is used in areas of known deficiency. In some countries, planting covcr crops such as oats is a common practice. It is used with 200 kg/ha supper phosphate and 100 kg/ha urea. The oat is incorporated a: 4-6 weeks before bud break. Additional 150 kg ha of NPK (8:8:27) mixed fertilizer is suggested for late application (Cook. 1966; ll>67).

[116] The Grapevine

I r r i g a t i o n Adequate level of soil moisture should be maintained in the production of tabic grapes. ^ Irrigation of table grapes should therefore be regulated in order to maintain moderate and continuous growth of berries. Excessive irrigation may give large "watery" berries lacking in flavor. Watery berries do not keep well, are less palatable and brings poor prices. In drought years, non-irrigated vines may produce bunches with soft, immature and poorly sized berries. In low rainfall areas, irrigation should be reduced before harvest with utmost care to avoid moisture stress development if harvesting is prolonged. Furrow irrigation (under vine) is preferred for table grapes production. Sprinkler irrigation, despite its high initial investment, often is desirable; but it may cause softening and splitting of ripening berries. It may also increase the risk of fungal Giscases. Drip irrigation, in spite of the high initial cost, is much more preferable especially from the water conservation point of view. The amount of irrigation required varies with varieties, soil types and the season (natural rainfall). Areas /regions with adequate rainfall, requires less irrigation than those with less rainfall. Light sandy soils need less water but more frequently as compared to heavier clay soils.

Treatments t© improve grape quality

Adjusting crop load Quality varies with the fruit load on individual vines. The primary aim in grape culture is to maximize yields while maintaining high fruit quality. This can be adjusted at pruning time and later through thinning the shoots and fruit load.

P r u n i n g The level of pruning should be adjusted according to the variety and vigor of vines in order to maintain desirable balance between crops and foliage. Heavy pruning will encourage excessive vigor with associated poor set, poor disease control and improper color development. Majority of the table grape varieties bear satisfactory crops when spur pruned. Fruit load and shoot vigor govern the number of spurs to be left on a given vine. Usually 10-16 well-spaced spurs per vine arc ideal for most varieties. Ugni blanc is normally pruned to spur 2 -4 nodes in length while Thompson Seedless vines are pruned to longer, 14-nodes cancs. Spurs are left as replacement cancs for canc- pruned varieties.

•Shoot thinning Shoot thinning is the removal of unwanted and unproductive shoots. The term de- suckering is incorrectly used, as a sucker is a shoot arising from below ground. Shoot thinning is done to open up the vine capacity' thereby improve the ventilation and exposure of the remaining shoots. Shoot thinning is normally started when the shoots develop about ten visible internodes and continued until soon after set at 2 0 visible nternodes. Early shoot thinning may force new shoots from buds on the cordon. In general, all shoots other than those growing from the spur retained at pruning time arc

[117] Asfaw Zelleke removed while in the case of canc pruned varieties all barren shoots are removed unless they are needed for shading or as replacement canes in the following season. It is however important to note that a moderate degree of shoot thinning is an advantage In vineyards with limited water supply in order to reduce the vines' water needs. Excessive shoot removal might also weaken young vines.

Fruit thinning Removal of flowers or clusters or berries is referred to as crop thinning. Fruit thinning offers the opportunity for selectivity and quality improvement of berries. Flower cluster thinning, cluster thinning and berry thinning arc discussed.

Flower cluster thinning Flower cluster thinning is also called inflorescence thinning. This type of thinning is carried out before flowering on varieties that tend to set straggly eluster bunches. The remaining inflorescences are better nourished and set is thereby increased with a ttractive bunches.

Inflorescence tipping (removal of small portion of a cluster) is also practiced to improve the appearance of the bunch in some varieties that set large bunches and/or have poor set and berry size.

Cluster thinning Culling or sorting of bunches at early stage of berry development is called cluster thinning or bunch thinning. It is basically, removal of undesired and poor set bunches. Cluster thinning is done after flowering or preferably after fruit set. This practice is useful during the first few bearing years when fruitlessness is high but reserves arc low becausc of the limited development of the root and stem systems. The bunch shape and size are regulated by bunch tipping after fruit set. The degree of tipping varies with different varieties. Some varieties require heavy bunch tipping to produce small attractive bunch that is better marketable.

Kerry thinning Berry thinning refers to removal of berries. This is carried out soon after berry set on individual bunch as of varieties that set over-compact bunches. It must be completed before the berries are large enough to touch each other, i.e., during the first growth phase. If it is done properly, it gives looser bunches, larger berries, better color development in eolored varieties and reduce the risk of bunch rot at harv est. Berry thinning is time consuming and labor intensive; but the results are rewarding. However, in certain varieties, to obtain a well-formed bunch, more than half the berries cn the bunch may have to be thinned. Bern7 thinning can be done by a process called "milking" which consists of running thumb and forefinger or a hairbrush quickly down the bunch stem to remove a portion of the berries and bunch laterals just prior to shatter.

[118] The Grapevine

Treatments to improve berry setting Berry set can be improved by applying physical and chemical treatments to the vines at specific stages during growth and development of vine. These treatments include:

Physical treatments Girdling: ir is the removal of a complete ring of bark, 3 to 6 mm wide from the trunk, arm or cane anywhere below the fruit. It is usually practiced in table grape varieties. The main purpose of girdling is to improve set. increase the size, improve coloration and hasten ripening of berries. Girdling is done at different times and stages of berry growth in order to achieve the purpose. Thus, to improve set it should be done at bloom time (mostly seedless), during the period of most rapid growth (few weeks after bloom) to increase berry size and at early verasion to improve color and hasten ripening (Peacock et al., 1977).

Topping and tipping: removal of 10 cm or more of the shoot is referred to as topping while tipping is removing less than 10 cm of the shoot tip. This is practiced to improve berry set by reducing competition for food materials between two strong sinks, i.e., the shoot and the developing berries. Topping is carried out 4-7 days before the peak flowering. In some countries growth retardants are used, instead.

Chemical treatments 'o improve berry setting most often two types of growth regulators are used to influence berry setting (Coombe, 1970). These arc the promoters gibberellins (gibbcrellic acid or GA_0, and the retardant CCC [(2-chloroethyl)-trimethylammonium chloride].

Gibberellins (GA3): application of GA3 is effective in seedless grapes. Gibberellins (5-15 mg/1) sprayed on flowers at anthesis reduce the number of sets (Weaver, 1972). It can also improve set and berry size of male-stcrol varieties like 'Kai Dubic' (local cultivar).The yield and appearance of 'Kai Dubie' can be improved with application of 5-20 mg/1 GA3 just before the shatter stage .

CCC [ (2-chloroethy 1)- trim ethylam m onium chloride] Application of CCC to either the foliage or bunch, from one to three weeks before bloom, may increase fruit set by 2 0 % in several seeded and seedless vinifera grape varieties. Similar results were also found with growth retardants Alar (N- dimethylaminosuccinic acid) (Coombe, 1970).

Treatments to increase berry size Spraying vines with GA3 at different stages of berry growth and development can mprovc berry size, elongate bunches, reduce beriy number and enhance maturity. The influence of GA:, on each of these parameters is discussed in brief based on the indings of Weaver (1972).

[119] Asfaw Zelleke

Increase berry size Gibbercllin is the most widely used growth regulator in all tabic grape growing countries of the world. According to Weaver. GA* is used to improve berry ^ development of seedless grapes especially Thompson Seedless and Black Corinth. Application of GA3 (2.5 to 20 ppm) at bloom time, when cap fall is between 20 to 80%, can increase berry size. This is done by thinning the dusters or by reducing berry set by GA? treatment. Berry' size could also be increased by a second application of GA? (20 to 40 ppm) at fruit set (berry shatter) that is about 10 to 14 days after the first application. Further GA, (20 ppm) at 80 - 100% cap fall is better for enlarging small parthcnocarpic berries and treatments at 30-40 days after full bloom, can also enlarge seeded berries of some varieties responding to GA. However, an earlier treatment of GA3 has greater effect on berry enlargement of seedless varieties.

Improve bunch elongation GA3 also affects bunch elongation. Spraying bunch-stem with GA:, (20 - 40 ppm) when bunches arc half to two-thirds of their final length cause them to grow longer than normal. It also helps in preventing excessive compacmess and thereby resulting in loosening of clusters. l&educe berry number The ultimate effect of berry thinning is increase in berry size, which is mainly due to elimination of competition amongst developing berries for assimilates. Spraying GA? (|2.5 - 20 ppm) 011 flowers at anthesis reduces the number of berries set on the bunch iiC. it produces thinning effect. The treatment also inhibits seed development and may induce sccdlessness in normally seeded varieties.

Enhance maturity The time of GA? application affects the rate of maturity. Application of GA? between the beginning of flowering and bloom time enhances maturity, but if applied later, it may delay maturity.

treatments to improve color and enhance ripening

iprovement of berry color cphon (2-(choloroethylphosphonic acid) has been implicated in the physiological role of color improvement in certain varieties (Jensen and Andris. 1977). Application of ethephon at 300 mg/1 at 5-10% color dev elopment stage demonstrated the most consistent results with certain varieties (Jensen e/ al., 1975).

Hastening of ripening Grapevine bunches can be manipulated in various ways to hasten ripening and to obtain early harvest. Chemical treatments such as hydrogen cyanamide at 1 to 5 % just after pruning can stimulate early bud break. The ability7 of hydrogen cyanamide to stimulate earlier and uniform bud burst is well-documented (Zelleke and Klievvcr. 1986; 1989).

[120] The Grapevine

Maturity and maturity standards Tabic grapes arc ripe when they attained attractive color and become palatable. At maturity, the berry develops its distinct flavor and color characteristics and becomes soft. The requirement for minimum maturity standards varies considerably for the different varieties among developed countries. In general, maturity standards are based on total soluble solids (TSS) concentration and titratablc acidity (TA). TSS concentration is determined with refractomcters and TA is measured by titration with standard NaOH (sodium hydroxide) to a phenolphthalein end (pH 8.3). The TSS/°Brix:acid ratio (the ratio of °Brix to TA as tartaric acid g/100 ml, of juice) is widely used as a maturity index for table grapes. Judging the minimum acccptablc level of maturity is a problem of growers especially with early varieties. Unripe grapes may have an adverse reaction by consumers, which may affect reputation and future saies prospccts. Conversely, over-ripe berries are subject to handling injuries, disease, and poor appearance. However, the physical appearance of berries is the best index for die experienced growers. The color of the bcrrv, condition of bunch stems and berry taste arc used to determine ripeness. Thus, black and red varieties usually show bright color when ripe, while white varieties develop a semi-translucent appearance.

Pre-harvest protection Botrytis rot (Botrytis cinerea) is a major fungal disease of grapes in both the field as well as storage. Botrytis is a common problem in all-major grape growing countries of the world following late season rains. Its infection usually occurs at blooming but the fungus remains dormant until verasion when it resumes growth and rots the berry. Proper field spraying program and management techniques are the best means to control the disease.

Harvesting Unlike the other grape types, harvesting table grapes is an expensive operation. Picking bunches, trimming and packing operations arc highly labor intensive. Bundles that have good eating, shipping and keeping qualities should be harvested. Harvesting should be done early in the morning when the weather condition is cool enough to reduce the amount of water lost from berries. The grapes are held up by the bunch stem during picking and trimmed to minimize loss. Harvesting should be done under dry conditions after rain or wet weather.

Bunch trimming To improve the appearance of the bunch, immature, diseased, split, shriveled and Doorly colored or under sized berries should be trimmed.

[1211 Asfaw Zelleke

Packing and shipping

Packing Table grapes are highly perishable commodity. It is therefore, necessary that the fresh fruit is handled properly in the field and in transit so that it reaches the consumer in good condition. Table grape packing can be done in the field or in the house depending on the size of the operation, skill of the workers, and availability of packing materials and/or facilities.

Field packing Field packing is recommended for varieties that do not stand re-handling well or easily damaged varieties. It is often used for early maturing varieties. It has the adv antage of limiting loss of bloom and damage to the berries. In the developed countries, experienced workers harvest, trim and pack the grapes dircctly from the vines in the field. The packed boxes/containers are left in the vine rows. A tractor forklift with a pallet collects the boxes and delivers them directly into a cold room where they arc kept until ready for shipping.

IRow packing The pickers select, pick, trim and pack the grapes in the container. Row packing is the least expensive of all the packing systems. However, it requires experienced pickers.

Roadway packing This operation is done along the roadways of the vineyards. The packers pick, trim and place the fruits in field box and carry the full box to the roadways. Skilled packers do the packing on benches equipped with scales. The packs are uniform and adequate supervision is relatively easier than row packing.

!>hade packing The grapes are harvested and carefully placed in a container for transportation to the shade packing. The packing shed is equipped with adequate light, ventilation, and ample room for storage and working space.

House packing Flouse packing is a highly centralized operation, and skilled workers do it. The pickers remove selected dusters and place them carefully in field lugs, with the stem up and one layer deep. The packing house is equipped with packing benches and scales. The packers trim and pack the fruit into the proper containers. House packing is a more expensive operation than field packing. It is usually recommended for large vineyards. Table grapes are packcd both for the domestic and export markets. The requirements for the domestic market are not as stringent as for the export markets. The export markets have certain requirements that should be fulfilled. These requirements vary from country to country and the competition is quite keen. Generally, table grapes are one of the premium fruits imported into the developed countries and as such arc considered a luxury commodity. Therefore, the demand is extremely high for premium

[122] The Grapevine g ft-pack type grapes. It is important that the grapes are sweet with low-acidity. large- sized (20-30 mm) seedless, with fresh green stalks and medium sized bunches (500- 600 g) and reasonably matured to satisfy the style preferred by most countries. Grapes are packed in a range of containers using different packing styles. Generally, fruits are packed by variety and arc graded as Extra Class, Class 1 or Class 2 grades (Nelson. 1979). The style of packing is either the bunch-stern down or bunch-stern up (face pack) with the stem hidden. The latter system produces an attractive pack with an even layer of grapes facing the buyer. This system is being replaced by the stem-up pack style, which allows buyers to remove, bunches easily by the stem thus minimizing berry damage. This is now widely used in most table grape producing counties. The most widely used container/package is the standard half-casc or carton with internal dimensions of 45 cm long, 30 cm wide and 15 cm deep. The main function of package is to protect and identify- the packed berries. It can be constructed of timber, or fbcrboard or cartons with a capacity of 10 kg grapes. Cartons are usually the preferred packaging even though it requires great care as compared to timber case.

Post-harvest handling

Pre-cooling Cooling is important primarily for grapes destined to distant markets and/or for long­ term storage. It is necessary that the field heat should be removed rapidly from the grapes as soon as they come from the field. The rapid reduction of heat from the grapes has ccrtain advantages (Ginsburg and Triter, 1976). These are:

® Reduce the loss of moisture from the grapes, which reduces (lessens) wilting stem desiccation, browning and bcrrv shatter; ® Reducc respiration rate of grapes thus prolonging the storage life: and « Slow down the rate of growth and development of decay causing organisms.

Good quality of grapes is preserved, if they arc pre-coolcd (<10°C) immediately after harvest.

Cold storage Cold storage can hold fresh grapes for longer time by reducing water loss, fungal nfection and fruit spoilage. Thus, cold storage helps to regulate continuous supply of 'ruits to the market after the end of main grape season. It is important that cool stores arc properly designed and constructed. The total quantities of grapes to be stored, the daily rates of loading, the temperature of grapes going into store, the desired rate of cooling, the required storage temperature and relative humidity need special attention while determining the specifications of the stores (Ryall and Harvey, 1959). Therefore, following properly packing and pre-cooling operations, the success of maintaining the quality of grapes is greatly affected by storage environment such as temperature, relative humidity, air movement and fumigation with sulfur dioxide as discussed below.

[123] Asfaw Zelleke

Temperature Fruits can be stored longer at lower temperatures. The recommended temperature for the grape is 0 -lnC. Grapes will freeze at near - 1,5°C.

Relative humidity A high relative humidity (96%) is recommended. An increase in relative humidity will decrease water loss from the grapes.

Air movement Adequate air movement should be provided to remove respiratory heat and maintain sufficient levels of oxygen. The store should be equipped with a cycling fan and a compressor to regulate the air movement as often as needed.

Fumigation Botrytis cinerea, Clcidosponum herbarium, Penicillium spp. and Alternaria spp., may :ause serious loss in grapes even under low storage temperature. Regular fumigation with low levels of sulfur dioxide controls the spread of storage fungal diseases on the merries. Sulfur dioxide also prevents bunch stem from turning brown or black in storage. It reduces berry shatter and the rate of respiration. Different methods are used to apply sulfur dioxide. The reader is referred to Nelson and Gentry' (1966) and Winkler et al. (1974) for more information.

Storage life of table grapes The keeping quality of table grapes varies with variety. Some varieties show significant loss in few hours (4-6 hr) while others can be maintained for about 6 months (Winkler et al.. 1974). Storage faults also vary with variety because some varieties develop a distinct browning of skin in cold storage, which gives the berry a dull and imperfect appearance while berries remain sound and firm. The quality of tabic grapes therefore, can be maintained for at least six months in the cool store under optimum management practiccs with adequate facility.

Marketing Table Grapes The condition of the grapes determines the market price in the global markets. Table grapes must be handled with care to avoid a loss of quality (Nelson, 1979; Keenan, 1980). Low temperature and high humidity arc essential to preserve the quality of table grapes. Extra care is required to maintain this condition throughout the whole marketing chains. Low humidity and excessive condensation on warm fruits will aggravate fungus rot.

Kaisin Grapes

The grapes that produce an acceptable dried product arc included in this category. Raisin is a dried fruit of certain varieties of grapevines bearing berries with high sugar concentration (25 - 27 °Brix) and low moisture content (<15% moisture). The word raisin means dry grape from the French raisin sec. Hence, any dried grape can be

[1241 The Grapevine callcd raisin. Wine and tabic grapes arc occasionally dried. These should be callcd dried grapes to distinguish them from the normal raisin grapes. Unlike the wine and the table grapes, there arc only few varieties of raisin grapes. Thompson Seedless, Muscat o ' Alexandria, and Black Corinth are the examples of raisin grapes (Winkler et a l, 1974). Seedless grapes possessing soft texture, a marked and pleasing flavour, seedlcss-ness, large or small size after drying (depending on market demand), earliness, case of drying, and little tendency to become sticky during storage are considered as good raisin grapes .

S uitable areas £©r raisin production Climate is the major determining factor influencing the selection of areas/regions suited to raisin production. The sun drying rate of grape berries closcly follows the evaporation rate for a particular region and season. Thus, climatic conditions that provide a high evaporation rate (low rainfall, low relative humidity, high temperature and rapid air movement) arc the most suitable ones for drying grape berries for the production of raisins. Suitable regions arc distinguished as hot or very hot with heat summation exceeding 2000-degree days of the hottest month exceeding 23 C, according to Winkler and his coworkers. These areas/regions arc situated between 25° south and 40° north latitudes in both hemispheres. However, regions with the low rainfall usually require irrigation to supplement the natural rainfall for good crop production. The major raisin producing regions of the world are Upington (South Africa), Mildura (Australia), Patras (Greece), Izmir (Turkey), and Kandahar (Afghanistan). These areas/regions have the most favorable climate for raisin production with Mershcd (Iran), and Fresno (USA) also as good favored ones (Winkler et a l, 1974).

Harvesting and drying grapes

Hand Harvesting Proper handling of fresh berry is critical for the production of high quality raisin. Broken or damaged berries stimulate or enhance the browrning reaction and cause dark berries. Harvesting should be done carefully. Weed seeds or any other contaminant will cause problem both for processors and consumers. The technique used in the production of raisin differs from placc to placc. In the majority of cases, raisins produced in the world are hand-harvested that involves canc pruning harvest and/or eluster harvest.

Mechanical Harvesting Mechanical harvester is usually recommended for large acreages of commercial production so that harvesting should be done in relatively short time (May et a l, 974). In this method, cancs bearing fruiting shoots arc cut and left on the wire until the cluster stems arc dried. This usually takes about a week depending on the weather. This method, even though is much efficient for common production of raisins, the effect of cane cutting on the subsequent performance of vines, and potentially large

[125] Asfaw Zelleke

Sized berries to dry entirely into raisin are not well documented. Nonetheless, the reader is referred to Studer and Olrno (1971) for detailed information. drying

Degree of dryness At harvest, grape berries have about 80 % water content. Raisins should not be over dried since the fruit will lose its texture. If these limits are not exceeded, the fruit should keep well during prolonged storage and necessary moisture can be added during processing at the packinghouse without risk of spoilage (Winkler et a/., 1974). It is not easy to determine accurately the moisture content in the products. One has to depend on skill acquired with experience However, when a handful of raisin is squeezed, they should feci pliable and when released they should not stick together to form a ball, but separate immediately and return to their original shape. Thorough drying is neccssary to maintain the good keeping quality of raisins. The relationship between moisture and keeping quality has been well-documented (McBean et al., 1971). Raisin should contain about 13-15% moisture. As a rule, it should not be possible to squeeze out any syrup from well dried raisin with the fingers. According to Winkler and his coworkcrs, drying of grapes involves the pre- drying treatment and the actual drying treatment that follows. Each is discussed in brief.

Pre-drying treatment process Different drying processes of raisins have been used in many raisin producing countries since time immemorial. Most raisin varieties are dried by the natural nethods. In most developed countries very few of these varieties are either dipped or .ulfured (to produce the so called “golden-bleached and sulfur bleached colors), soda oil dipped, before drying. Winkler et al. (1974) describe each of these procedures as ollows:

Golden-bleached Raisin variety (Thompson Seedless in USA) is mostly produced by the ‘lgolden- bleached” (light colored) process. Treated raisins are brilliant lemon yellow to golden yellow color and arc tender. The golden bleachcd process is one of the methods and it is described as follows (Newman, 1985):

• Select clusters that have healthy, mature and well ripened fruits/berries • Dip the fruits/berries for two to three seconds in boiling solution of 2000 to 3000 ppm or 0.2 to 0.3% caustic soda (sodium hydroxide) • Expose moisten fniits for 2 to 4 hours to sulfur fumes or sulfur dioxide in a sulfur house (0.45 to 1.8 kg of sulfur per ton of grapes) until the fniits acquire a unifonn light yellow color • Dehydrate fruits/grapes at 60° to 70°C to ^et a brilliant lemon yellow to golden yellow colored raisins.

[126] The Grapevine

SulSur bleaching The initial steps (a-c) of preparing the raisins for sulfur bleaching are almost the same as above.

• Sclect cluster in the same manner as above • Dip fruits in boiling solution of 2.5 kg of sodium sulfate [(Na^SCM)], 0.3 kg of caustic soda and in 100 L of water for 4 seconds ® Dehydrate fruits as above • Spread fmits on wooden trays in the sun for 3 to 24 hours depending on the weather condition • Flip fruits/grapes over into an empty tray to dry them. The finished product looks waxy with yellow white color.

Soda-oil dipping Soda -oil dipped is done by the following processes (Winkler et al., 1974). ® Dip fruits/grapes for 0.5 to 3 min in a warm (37°C) cooking soda/sodium bicarbonate (3.5 kg) and caustic soda (112 g) in 100 L of water with a film of olive oil floating. ® Drain the dip and dry fruits in the sun until finished product looks dark color with slightly oily surface OR ® Dip in warm (70°C) cooking soda with a film of olive oil floating on the surface • Drain the dip and dry the grapes as above

Soda dipping (hot dipping) The process involves the following:

• Dip fruits/grapes for 2 to 3 sec. in a 2000 to 3000 ppm boiling (93° to 100°C) caustic soda (sodium hydroxide) solution in a small quantity of olive oil • Rinse fruits in fresh water and spread them on trays in the sun • Flip or turn them over fruits into an empty irav and continue drying for 2 to 3 days more. Finished products are translucent with distinct brown color.

[Drying processes The drying process in general involves the evaporation of water vapor from the berry/fruit surface and the removal of the water vapor by air movement. The different drying methods are discussed as follows.

In situ on the trellis Canes arc cut by hand at the correct place with leaves intact to ensure that most of the fruits will be dried on the trellis. The best time to harvest trellis dried fruit is in the afternoon when it is not too hot.

[127] Asfaw Zelleke

Drying on the ground/Sun drying The simplest method of drying grapes is to spread fruits onto sheets on the ground where the sun provides the heating to evaporate the water and the wind removes the vapor. This form of drying is known as “sun drying’'. It is done by spreading the grapes onto water proof plastic sheet on the ground and spread out to absorb sun radiation. It lakes 2 to 3 days to dry the fruit down from 16 - 17% moisture to below 13%. The grapes should be spread to a depth of about 2.5 cm or about 3 berries thick to enhance the drying rate (Clingeleffcr, 1984). However, under unfavorable weather conditions, fruits/grapes should be covered over night and reopened when conditions are suitable. Sun drying is different from dehydration. The latter involves the heating of air by fuel powered burners and increasing the air velocity by using fans.

Drying on rack This form of raisin drying is different from the two forms mentioned above. This system is used for drying large quantity of grapes at a time on racks made of either wooden or steel shelves (Gmcarevic and Lewis, 1976). The length of the rack varies from 40 to 90 m; about 1.5 m wide and 3 to 4 meter high with about 30 cm between shelves with a roof on top. The racks are oriented north-south to promote more evenly exposure of fruits to the sun and also to the advantage of the prevailing west winds. Two types of drying are practiced in developing countries and this involves dipping before spreading on rack and spraying after spreading (Whiting and Morey, 1988). In either case freshly harvested grapes of 23 to 26 °Brix are loaded directly onto the rack after being collected from vineyards. The two forms are discusscd.

Dipping emulsions The dip emulsion contains 2.4 kg of potassium carbonate, 114 g sodium hydroxide (caustic soda) and 1.5 L drying oil in 100 L of water (May et al., 1983). About 250 kg of the fruits are immersed in a tank of the dip emulsion for 1 to 3 min at a time. Half­ strength of the dip emulsion is also applied under unfavorable weather. Then, draining the grapes and evenly spreading them on the drying rack is followed. Spraying the grapes on the drying rack with half-strength dip solution after 4 days will hasten drying.

Spraying emulsion This method avoids the use of a bulk dip and is quicker. Fruits are loaded directly onto the rack after being collected from the vineyard. Spraying emulsion that contains 1.8 kg of potassium carbonate and 1.0 L of drying oil in 100 L of water is prepared and a ton of fresh fruit is sprayed with 60 L of the solution using series of nozzles attached to a spray unit (Winkler et al., 1974). When bunches are partly shriveled (after 5days) a sccond application at half-strength is applied to wet berries missed by the first spray. Puck spraying need to be done thoroughly to avoid uneven drying and fruit color. The two systems are followed by removing the raisins from the rack when the moisture content is about 18%. Then, the raisins are spread on the plastic sheet on the ground for finishing. In favorable weather, the raisins may dry to 13% moisture within 1 to 3 days.

[128] The Grapevine

Continuous racking may be neccssary to obtain desirable and uniform light amber color. Post-drying and other quality factors Raisins arc ready for consumption after drying, curing, cleaning, stemming and sorting. The success of the packing process depends upon the care and skill of growers right along the way from growing until delivered to the packinghouse. Care taken to dry the raisins thoroughly and store them properly contributes to the success of the operation. Important factors that affcct the quality of raisin are discussed based c n the information from Winkler et al. (1974).

Curing 'he raisins are put into boxes for the curing process. In the process of curing, moisture is transferred from wet to dry raisins by direct contact or evaporation into the air spacing. Moisture equivalent is computed when the moisture content is satisfactory.

Vineyard storage Dried raisins should be delivered to the packing house within four weeks after they are removed from the trays. Best storage condition should be provided at the vineyard, 'he store should be clcan, cool, dry well ventilated and lighted. Strict control measures are required to avoid possibilities of any contaminants with the raisins.

Quality factors Certain conditions affect the quality and food value of raisins. Flavor, seediness and secdlessness of raisins are function of the variety and drying methods. Color, flavor, texture are affected by the methods of drying. According to Winkler and his coworkers, the most important factors that affcct raisin quality are discussed below.

Size of berries The grape berry determines the size of raisin. The size of berries within the same variety may differ between vineyard locations. Crop load generally affects berry size. The heavier the crop load, the smaller is the berry size.

Uniformity and brilliance of color vlaturity of grapes and favorable drying conditions affcct uniformity of raisins. Similarly, maturity and soundness of fruit determines the best color. Best color is obtained from yellow/cream colored and well-matured grapes, which are dipped and dried under clear hot weather conditions. Dark colored or partially broken grapes are not suitable for making raisins. Brilliant color is obtained after preserving the natural bloom on the grapes, and followed by careful harvesting and picking the raisins and drying them on trays.

[129] Asfaw Zelleke

Condition of berry surface Raisins should be clean and dry. Over dipping and bleaching may cause die skin of berries to peel off and gather dirt that is difficult to remove

Texture of skui and pulp Matured grapes are suitable for making quality raisins while immature berries are not. The latter, often have hard and tough texture. Good quality raisins are plump, pliable ind meaty. Other desirable characters such as, tenderness of skin is also a function of lie variety and the drying method.

Moisture content The desirable moisture content of raisin is between 13 and 15 % (Gmcarevic, 1969). The moisture content should be neither above 18 % nor below 10 %. Low moisture level can be adjusted by moistening the berries to the desirable level. If it exceeds the 18 % level, it is likely that it will deteriorate in storage.

Chemical composition The degree of maturity affects the chemical composition of berries. Well-matured grapes (°Brix > 20) arc high in sugar and low in titratable acidity. The quality of iaisins is affectcd by sugar, acid, and salt lev els (Table 15). In general, the chcmicai composition and hence the food value of raisins is almost equivalent to fresh grapes with the exception of some vitamins, which are deficient in raisins (Table 16).

Decay, mold, yeast and other foreign matters "he weather conditions during harvesting and dry ing, affect the quality of raisins. As indicated above, the maturity of the fruit primarily affects the quality of raisins. Similarly, the drying conditions also affect the quality of the raisins. In this regard, a rain during drying or the use of decayed/rotten or moldy grapes can cause decay and mold growth on the raisins. Insufficient day temperatures may allow yeasts to grow on the raisins. The degree of berry infection by yeast and mold and decay directly influence the market value of raisins (Winkler et al., 1974). Decayed or molded raisins have no market value. Sticky raisins or wet raisins (rain) are easily affectcd by foreign materials, which when adhere to the raisins, it will be difficult to clean .

Infestation by insect or insects F'roper sanitation measures should be employed to control insect infestation of grapes/raisins or to eliminate the insects at the various stages of its development.

Maturity of grapes vs. yield and composition of raisins Water and sugar arc the main constituents of mature grapes. The water content of berries decreases while the sugar level increases as maturity advances. During the drying process, the sugar content of raisin increases while it loses most of the water content. Hence, at harvest, the sugar content of grapes is greater and consequently the greater will be the yield of raisins and the higher their quality (Antcliff, 1967). Table

[130] The Grapevine

15 shows the relationship of the moisture content, drying ratio, the sugar and acid contents and sugar: acid ratio, and berry weight of sun-dried raisins.

Drym g rati© The drying ratio (weight of fresh grapes divided by weight of raisin produced at 15 % moisture level) shows that as maturity advances, sugar level increases; while the acid and moisture contents and fresh weight decrease (Grncarevic, 1973). Consequently, the sugar : acid ratio decreases as maturity advances. Increase in yield of raisin per ton of grapes for each °Brix is about 10.4 kg in sun drying methods and to produce 1.0 ton raisins, 4.3 ton fresh fruits arc necessary (Winkler el al., 1974). Thus, during the process of drying 3.3 ton of water should be evaporated. The waxy cuticle of grape berries hampers the process of drying. This increases the drying time considerably. High humidity and frequent rains remove the waxy cuticle effectively.

Chemical composition acid weight berries

Sugar content "here is an apparent increase in sugar content of grapes up to "Brix 23. Above this, the increase in sugar content is minimal (Table 15).

Acid content '.lie global trend in contents of grapes is a decrease in acidity as the sugar level increases towards maturity. Acid content in raisins is affected by processing method due to oxidation of the acids, which is higher than in dehydrated methods.

W eight ©£ raisins The dry weight of raisins is determined by weighing counted number of berries at constant moisture level, usually 13-15 %. Weight of berries increases as maturity advances. This indicates that increase in dry weight is a function of the level of sugars ni berries. Size of berries determines the final use of raisins. Hence, large berries are desirable for marketing dessert raisins, whereas, size is less important for cooking and baking. Color and texture arc rather important in the latter group.

[131] Asfaw Zelleke i able 15. The influence of grape maturity (°Brix) on drying ratio, sugar and acid contents and weight of 100 Thompson Seedless berries (15% moisture)

Maturity Drying Sugar Acid Sugar: acid Weight of 100 (°Brix) ratio (%) (%) ratio berries (g) 17.8 4.88 66.6 3.09 21.6 26.1 19.6 4.51 68.3 2.53 27.0 31.4 21.0 4.26 68.9 2.38 28.9 35.6 22.0 3.97 69.0 2.10 32.9 38.2 23.1 3.82 69.4 1.88 36.9 39.7 24.2 3.63 69.3 1.79 38.7 39.0 24.7 3.50 70.0 1.64 42.7 42.9 26.9 3.26 69.3 1.57 44.1 47.2 Source:Winkler et al. 1974 as adopted from Kasimatis and Lynn 1967

Table 16. Mineral, vitamin and other food composition of Thompson Seedless raisins

Mineral Quantity Potassium 708 - 950(mg/100 g) Calcium 50- 78 (mg/100 g) Magnesium 20- -41 (mg/100 g) Phosphorous 9 4 - 129 (mg/100 g) Iron 1.5 - 3.3 (mg/100 g) Sodium 1 3 -8 7 (mg/100 g) Copper 0.22 (mg/100 g) Carbohydrates 76 (%) Proteins 2.5 (%) Fats 0.6 (%) Crude iber 0.95 (%) Ash 2.1 (%) Thiamin 100- 120 (microgram /100 g) Riboflavin 25 - 30(microgram /100 g) Nicotinic acid 620 (microgram/100 g) Pantothenic acid 55 - 60(microgram /100 g) Pyridoxin 230 - 240(microgram /100 g) Biotin 4.0 - 4.48 (microgram /100 g) Folic acid 10(microgram .100 g) Vitamin A and C Nil Source: Winkler et al. 1974

Marketing In Ethiopia, the local demand for raisin is extremely high. The Churches and the pastries are importing large quantities of raisins for their specific uses by spending exuberantly huge sum of foreign exchange. It is important that the establishment of a raisin industry receives due recognition and concerted efforts should be exerted to produce enough raisins and satisfy the local demand with the ultimate goal of producing more for the export markets as well at least to the neighboring countries. drapes £or Other Purposes Juice grapes - Grapes producc acceptable beverage when preserved by pasteurization, germ-proof filtration or other means. The juice must be able to retain

[132] The Grapevine fresh grape-flavour. Concord, Beauty seedless, Early Muscat etc. are examples of juice grapes.

Canning grapes - Seedless grapes, such as Thompson Seedless are canned alone or in combination with other fruits, in fruit salad and fruit cocktail.

Thus, grapes can also be used for odicr purposes such as fresh juice and canning. However, unlike the other types of grapes there is no single variety recommended for the production of fresh juice and canning, though seedless varieties are preferred. The most desirable characteristic of fresh-juice grape is to retain its fresh-fruit flavor throughout the process. Depending upon the variety, the juice is cither sterilized or pasteurized. In most European countries, the juice from vinifera grapes is sterilized, whereas in the United States of America, Concord, alone or blended with other varieties, is pasteurized for making fresh juice. Therefore, the method to be used in processing the juice is usually decided by the variety of the grapes. The most attractive market for first-class quality fruit unequivocally, is the fresh fruit market and the market for raisins. An increase in availability of table grapes will also increase the amount of fruit rejected from the market. These fruits have to be processed very quickly into durable products, which can be stored. Depending on the amount, the simplest ways of processing are drying or the production of concentrate/syrup. The production of juice for the immediate consumption is possible, however, freshly pressed grape juices will start fermenting after a few hours. Therefore, for this type of alternative product, some technology is required. The product has a high nutritional value and is a good supplement to a healthy diet. Most grape growing countries arc exporting grape-juice in the form of grape-must concentrate. The concentrates arc used for making wines, jellies, jams or marmalades. In many of these countries grape- juice is available even in the smallest shops selling beverages on the road side. This indicates that there is probably good market all over the world for this product. For tropical areas, the production of concentrate (without addition of sugar) or syrup with the addition of sugar is "safer" than the production of grape-juice in terms of the hazard by spoilage. Additionally, less sophisticated technology is needed. Concentrates or syrup can be recommended for different scale productions, private persons, small growers, co-operatives, commercially operating large companies. In Islamic countries, concentrated grape juice is one of the major sugar sources of the people and is used to sweeten food, pastries and pies. The volumes of raw materials available at a given time affect the procedures employed in making grape-juice. Hence, for smaller amount of fruits:

• The berry (pulp, skin and seed) is slowly heated in a boiling pot or kettle. The pulp has to be stirred constantly until a viscous state is reached. The concentrate at this stage should be about 60% sugar. It can be stored for long periods in closed containers. • The berries are squeezed, pressed and the skins and seeds are removed through large sized sieve. After heating, a turbid, tasty, durable concentrate can be obtained; and

[133] Asfaw Zelleke

* Concentrate the juice by adding sugar to produce syrup. This can be used as a type of spread onto bread, for backing or can be re-diluted with water to make a simple beverage. The above methods are not suitable where large amount of fruits arc available. In this case, a simple production plant should be established, equipped with pressers and concentration facilities to produce turbid concentrates or even jellies or marmalade.

[134] The Grapevine Chapter IX

Varieties Fruiting Varieties

'"T^he grapevine has the oldest culture recorded than most cultivated fruit crops. More JL than 8,000 varieties of grapes have been named and described over the entire world. In Ethiopia, certain grapevine varieties have been introduced at different times probably starting from the time of the Italian occupation. However, the origins of these varieties are unknown. Consequently, they are given local names based on color and shape of the berries to differentiate them from one another. Since the late 1970s some known varieties have been introduced from Europe and the United States of .\merica. They were planted at different agro-ccological zones to study their adaptability. Sixteen wine grape varieties showed superior performance and following further verification trials, eight varieties, including a local and standard checks, have been released in 2004 cropping season. They are now under production at research centers, state owned farms and few private farms. The following lists provide some of the leading fruit bearing varieties for the wine, table and raisin grapes. These varieties were introduced into the country by the Debre Zeit Research Center with the assistance of the German Volunteer Service Program of GTZ. The list also includes some known varieties of rootstock. These varieties can be used in areas that have the potential for successful production of grapes. Fruiting varieties must be introduced, preferably grafted on proper rootstocks despite the fact that soil bome problems such as phyloxera and nematodes have not been found yet as a threat in the production of grapes in the country. Some recently established vineyards by investors, are importing rooted cuttings that are grafted on rootstocks.

Fruiting Varieties

Wine Grape Varieties Released Varieties: Eight varieties (one local check (Tikiir) and one standard check (Chenine blanc) are registered in Crop Variety Register in 2004 in Ethiopia

White Wine Varieties Chenin blanc (Standard check)* Origin France Description: Leading variety in France. It is used to produce premium white wines in Europe, United States, Australia and South Africa. In France it is most suitable for natural sweet-wine and sparkling wines production Young leaf: Downy above and felty below

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Shoot: Glabrous, mahogany red on side exposed to sun, with brown streaks on the back Cane: Clear beige with dark nodes Cluster. Medium; long conical, compact, winged Berries: Medium and oval shaped berries Vendril: Discontinuous, long thick and red Petiole sinus: Lyre shaped

Grenache blanche* Origin Spain Description: An important wine grape variety in Europe and USA. It is a productive variety with vigorous, upright shoots. It resists well both dry and windy conditions; fairly tolerant to powdery mildew. It is sensitive to botrytis and grape berry moth. Early to bud break and late to mature Young lea f: Plain green, pubescent Shoot: Green, shiny, glabrous with swollen nodes Cane: Clear straw yellow with dark longitudinal streaks Clusters: Medium, long conical, compact and winged Berry: Medium and oval Tendril: Discontinuous, small and thin Petiole sinus: V-shaped

1 Jgni blanc (Saint Emilion) * Origin Italy Description: Synonyms to Saint Emilion. It is very vigorous, regular producer, recommended for white wine; an important variety in France for the production of white wine Young leaf: Green with light brown streaks and brown nodes and petioles Shoot: Very thick, flat at the nodes, very distinctly ribbed, cobwebby at lip, brown in sun. darker nodes Cane: Straw yellow with dark nodes, bloom, longitudinal dark streaks; buds average, pointed Cluster Large and long clusters; shouldered, cylindrical; often branched at the tip Berry: Medium; round to oblate; white to pink Tendril: Large, well developed Petiole sinus: More or less closed lied Wine Varieties

B lack H am b u rg * Origin Germany Description: It is an important variety in Germany and many other European countries. Moderately vigorous variety; highly tolerant to powdery mildew but slightly susceptible to downy mildew Young leaf: Green and cobwebby Shoot: Clear green with a few brown streaks in sun, cobwebby at tip; tendrils green, medium

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('ane: Beige or clear brown with darker nodes, bloom covering specially on the nodes

(luster: Medium: shouldered and well filled Berry: Medium, round berries having a heavy bloom Tendril: Well developed (discontinuous) Petiole sinus: Overlapping (almost closed)

C a n n o n a n o * Origin Italy 1 description: This is an important variety for producing quality wine in Italy. Moderately vigorous, moderately susceptible to both powdery and downy mildews oung leaf: Plain green and cobwebby Cluster: Medium, compact and shouldered Berry: Small to medium; round to obiate Tendril: Discontinuous Petiole sinus: Lyre-shaped

Jodom Aleatico4 Origin Italy Description: This is an important variety for the production of red and black wines with Muscat flavor which is a natural sweet wine in Italy and other European countries. It is moderately vigorous; produce well Young leaf: Green with brow streaks and pubescence Cluster: Medium size: cylindrical, winged to double Berry: Medium large: oblate, reddish brown. Tendril: Discontinuous Detiole sinus: Overlapping, almost closed

Grenache noir * Origin: France Description: This is an important variety in Europe and the United States. Late to mid-season type. Vines are vigorous Young leaf: Plain green, cobwebby and shiny Shoot: Green, shiny, glabrous with swollen nodes Cane: Clear straw yellow with darker longitudinal streaks, nodes prominent, brown with bloom Cluster: Large to medium, short conical sometime shouldered or winged; loose to Compact Berryi Small medium, oval; brown to black Tendril: Discontinuous, small and thin Petiole sinus: Lyre-shaped more or less closed

Sangiovese (Tikur, Local check) Origin: Italy Description: This is an important variety mainly grown in Italy for the production of table wine. It is vigorous; moderately productive; A midseason variety Young leaf: Green with light brown streaks

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Shoot: Ribbed, clear green Cane: Beige with darker nodes Cluster: Medium size; cylindrical, shouldered or winged, well filled Berry: Small to medium; oval; brown to black Tendril: Discontinuous, small Petiole sinus: V-shaped, generally open

Other potential varieties of wine, table and raisin grapes are listed below.

French Colombard Origin France Description: A inidseason grape; moderately vigorous; with vineyard conditions; adapted to head or cordon training; sensitive to powdery mildew. Resistant to botrytis Young leaves: Downy, yellowish Shoot Brownish-green with partially pink node Cane: Orange-yellow, nodes slightly darker, no bloom Cluster Cylindrical, winged Berries Golden white, medium (12 mm), oval Tendril Pale yellow, thin medium length Petiole sinus: An open “V”

Muscat blanc Origin (Greece) Description: A midseason grape; vigour variety, low yielding; adapted to head or cordon training; sensitive to both downy and powdery mildews, and the grape berry moth (GBM) Young leaves: Cobwebby, shiny, and very bronzy Shoot: Streaked, brown streaks on side exposed to sun; flat node at the tip . Cane Yellow mixed with clear brown, dull, specked with black dots, darker streaking, light brown des. Cluster Medium, cylindrical, long narrow, compact rarely winged, compact. Berries Medium, round amber white, covered with rust coloured at the tip Tendril Large green Petiole sinus: Closed with parallel edges

Siauvignon blanc Origin: France Description: Vigorous; early season, sensitive to powdery mildew and black rot; fairly resistant to downy mildew and botrytis. Young leaves: Upper surface downy, yellowish with several patches of bronze; lower surface felty Shoot: Clear green with partially pinkish node. Cane: Clear beige with darker nodes (reddish brown on very thick canes) Cluster: Small conical Berries: Medium (9-11 mm), oval, golden yellow with slightly muscat flavour Tendril Small thin Petiole sinus: Narrow, almost closed

* Indicates released varieties i he Grapevine

S errrillost Origin France Description: Vigorous; productive; midseason grape; resistant to both downy and powdery mildews. Young leaves'. Downy, yellowish, bronze on the bulges Shoot: Green with pinkish brown nodes, very thick. Cane: Clear beige with darker nodes

Cluster: Medium, winged, cylindrical, and compact. Berries: Medium (12 mm), round white pinkish at full maturity, muscat flavour Tendril: Small thin Petiole sinus'. Lyre-shaped, generally open

White Riesling Origin: Germany Description: Early midseason, moderately vigorous; Adapted to cane pruning; sensitive to powdery mildew. Young leaves: Yellowish with copper patches, downy white Shoo/: Ribbed, reddish brown with pinkish ( ane: Fairly dark yellow with darker streaks, brown nodes with abundant bloom Cluster: Small, cylindrical-conical, compact. Be tries: Small round, clear green to golden yellow, delicate and aromatic flavour Tendril: Small thin and green Petiole sinus: Overlapping edges

Gewurztraminer Origin: Germany Description: Vigorous; early midseason variety sensitive to powdery' mildew Shoot: Ribbed, clear green with a few brown streak Young leaves'. Felty, yellowish; lower leaves have bronze patches Cane: Yellow brown with slightly darker nodes; light bloom nodes Cluster: Small conical, fairly loose. Berries: Oval, pink, thick skin, fruity flavour Tendri: Small thin P

Merlot Origin: France Description: Vigorous; productive; midseason grape; sensitive to downy and Botrytis Young leaves'. Downy, yellowish, bronze patches, 5-lobed Shoot: Brownish green with red streak. Cane: Clear beige, darker nodes with bloom Cluster: Cylindrical, medium (10 - 15 cm), loose, sometimes winged. Berries: Round (TO mm) blue-black Tendril: Tick, medium Petiole sinus: More or less closed

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Cabernet Sauvignon Jrigin: France description: A vigorous but small producer variety; midseason variety, susceptible to powderv mildew and phomopsis. has some resistance to Botrytis '"oung leaves: Downy, bullate. edges of ihc leaf reddish, giving wine coloured appearance ■>hoot: Ribbed, clear green, slighily brownish at the base Jane: Clear yellow to beige, reddish brown nodes, light bloom nodes 'luster: Small (10 cm), cylindrical-conical, winged terries: Round, small (7-10 mm), black, characteristic flavor endril: Small and thin 'etiole sinus: Lyre-shaped

’etit Syr ah Origin: France description: Low yielding variety, midseason variety, sensitive to drought, susceptible to Botrytis and GBV. resistant to powdery mildew, early season variety (oung leaves: Downy, yellowish-white above, felty, pinkish-whit below Shoot: Very ribbed, green with red nodes, downy at tip lane: Clear beige with darker nodes, abundant bloom Tluster: Medium (10 - 12 cm) c\ lindricaJ, pinecone-like. compact, woody peduncles terries: Small. Oval, blue- black, medium black abundant bloom . juicy and sweet Tendril: Long and thin Petiole sinus: Lyre-shaped, more or less closed

Pinot Noir Origin: France Description: An early season noble variety, which makes the famous red wines of Burgundy and a part of the sparkling wine of Champagne, has a wide range of adaptability but does well under wet humid condition; the compact clusters arc subject to Botrytis; a delicate plant, it requires good care for regular production; adapted to head training cane pnining Young leaves: Pale green, downy below, cobwebby above Shoot: Green with pinkish nodes and several streaks . ( 'one: Pale pink with dark brown nodes, greyish bloom covering the whole cane C 'luster: Small (7 - 10 cm), cylindrical, compact Berries: Slightly oval, blue-black, thick skin, bloom Tendril: Tick, medium Fetiole sinus: Lyre-shaped with narrow or overlapping edges

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Table Grape Varieties

Cardinal Origin: USA Description: Early season productive variety sensitive to powdery' mildew, downy mildew and pliomopsis. Young leaves: Glabrous, completely bronze Shoot: Glabrous, pale green, copper in sun, nodes slightly reddish ( 'ane: Clear orange,-brown with darker nodes and some streaks, light bloom on nodes ('luster. Large medium in size, conical; loose to compact Berries'. Berries are very large, cherry red to reddish black, round to .short oval not sweet and rather tasteless. Tendril'. Discontinuous Petiole sinus'. Lyre-shaped more or less open Pruning/training: Head/cordon pruning and long cane training

Emperor Origin: Unknown Description: A very vigorous, productive variety: late season variety, sensitive to downy and powdery mildews, cordon trained; suited for hot areas Young leaves'. Downy above with shiny orange patches; downy below Shoot: Glabrous , clear green, ribbed with deep grooves ( 'ane: Orange yellow with dark streaking-abundant bloom (7,luster. Voluminous, large (20 - 25 cm), attractive, conical, fairly compact Berries: Very large (>27 mm), obovoid, light red to reddish seeded, moderately firm Tendrii. Discontinuous, large Petiole sinus: Lyre-shaped with overlapping edges 1 ^runing/training Head/cordon pruning and long cane training

Flame Tokay Origin: Algeria Description: Late season variety, sensitive to downy and powdery mildews, cordon trained Young leaves: Glabrous bronze Shoot: Clear green, glabrous, purple in the sun ( ane: Reddish brown nearly mahogany with darker nodes and streaking, abundant bloom C luster: Large, shouldered, winged, conical and more or less compact Berries: Very large (25 - 30 mm), ovoid truncate, very firm, tough skin, pink to dark red, seeded, flat taste Tendril: Large Petiole sinus: Lyre-shaped Pruning/training: Head/cordon pruning and long cane training

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Malaga Origin: Syria Description: Late season variety. sensiti\e ;o downy and powdery mildews and Botrytis. cordon and/or head trained 'oung leaves', Completely bronze with very red bulges, felty white below hoot: Clear green on back, downy at tip. soft, nearly round, smooth with streaks Cluster. Large to very large, conical and well filled, attractive Cane'. Clear yellow-brown with darker nodes md streaking, light bloom 011 nodes. terries: Large (25 - 30 mm), uniform, neutral flavour, thick skin, white, seeded, ellipsoidal Tendril: Long petiole sinus: Lyre-shaped Pruning/training: Head/cordon pruning and long cane training

IPerlette Origin: Davis. California (USA) Description: (Thompson Seedless X Muscat Reine des Vignar), Vigorous and productive, cordon trained.-cane pruned, early season variety Young leaf: Shiny, glabrous Shoot: Ribbed, glabrous, green with red streaking Cane: Beige to straw yellow with darker nodes, bloom covering Cluster: Large medium in size, conical, shouldered: very compact require berry thinning terries: Medium size; round: white waxy, golden yellow, fleshy mild aromatic in flavour, seedless tendril: Discontinuous, very large 3etiole sinus: Lyre-shaped more or less open (some-times closed) pruning/training: Head/cordon pruning and long cane training lEttbier Origin: Oriental variety Description: A vigorous productive variety: subject to poor fruit set on lower part of the cluster: sensitive to downy mildew, tender to cold, docs not make good wine Young leaf: Downy, yellowish with bronze patches above Shoot: Clear green, streaked, downy at the tip Cane: Clear beige with darker nodes, bloom mostly on nodes Cluster: Large, conical; heavily shouldered; loose to compact, attractive, good shipping quality. terries: Very large: oblate to ellipsoidal; firmly attached; jet black; seeded. Good keeping and shipping qualities. Tendril: Discontinuous Petiole sinus: An open “U” sometimes closed Pruning/training: Head/cordon pruning and long cane training

Muscat Hamburg Origin: Germany Description: A very vigorous, productive, midseason variety, sensitive to downy and powdery mildews

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Young leaves Cobwebby, lobed, bronze patchcs Shoot: Clear green with a few brown streaks in sun, cobwebby at tip Cane: Beige or clear brown with darker nodes, bloom covering especially on the nodes Cluster. Large with well-shaped lateral branches, fairly compact Berries: Ellipsoidal, fairly large (15 - 20 mm), attractive blue-black, average skin. juicy pulp with strong muscat flavour, very pleasing Tendril: Green, medium Petiole sinus Lyre-shaped, more or less open Pruning/training: Head/cordon pruning and long cane training

Thompson Seedless Origin: Ancient Middle East Description: Early season variety, very vigorous and productive; cane pruned, grow best in warm areas, sensitive to downy mildew; require berry thinning, girdling and growth regulators to increase beriy size, fair shipping qualities. Young leaf : Glabrous, shiny Shoot: Glabrous, clear green, shiny. Cluster: Large; shouldered, long cylindrical well filled Berries: Uniform medium sized, ellipsoidal, elongated, greenish white, light to golden yellow, seedless firm and tender skin, fleshy pulp, seedless or with tiny seed traces; 'Tendril: Thin yellowish Petiole sinus: Lyre-shaped Primiirg/train iiig: Head/cordon pruning and long cane training

Raisin Grape Varieties

Black Corinth ' Irigin: Greece Description A midseason raisin variety Young leaves: Cobwebby, yellowish Shoot: Clear green with brown streaks, glabrous Cluster Medium to medium large, cylindrical, very narrow, compact Berries: Very small (5 mm), round or oblate, black, seedless or with very small atrophied seeds, thin skin, juicy flesh Tendril: Discontinuous Petiole sinus An open “V” shaped, some time nearly closed

Muscat of Alexandria Origin: Africa/Italy Description: A multipurpose variety (grape juice, table grape, raisin, aperitif or dessert wine), vigorous, pruned to long cane, late season variety, prefer hot dry region, susceptible to downy and powdery mildews and Botn-tis, Young leaves: Cobwebby, bronze patches Shoot: Ribbed, clear green with red streaks in sun, cobwebby at tip Cane: Straw yellow to clear brown with darker nodes, bloom at nodes Cluster: Medium, cylindrical-conical, winged, loose

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Berries: Ellipsoidal, large (20 X 12 mm), lo very large, fairly thin skin, fleshy pulp. muscat flavour Tendril: Discontinuous Petiole sinus: Lyre-shaped

Thompson Seedless (see under table grapes) l&ootstocks ~rhe adoption of the grapevines to certain environment as well as its ultimate growth mid development are usually controlled by the kind of rootstock upon which the fruiting variety is growing. Soil environment must be considered to determine the kind of rootstock to use. The proper rootstock should be used in soil borne pests areas where (phylloxera and nematodes) are a problem. There is also variation among rootstocks for adaptation to different soil condition. Some rootstocks adapt well in wet or dry areas, while others are highly tolerant to calcareous soil condition. The availability of several rootstocks for different purposes has significant importance for growing the grapevines under a wider range of soil and environmental conditions. The use of carefully selected rootstock has practically eliminated some of the major hazards in many grape areas of the world. In areas where soil pests and other soil condition (phylloxera and nematodes) are not a major problem, rootstocks are used to improve vigor, earliness of the vine and to improve the composition and hence the quality of the grapes/wine. Introduction of certain rootstocks should be given top priority in order to improve the quality of the grapes and at the same time to control the pest problem that might be of significant importance in the future. The following list, which is extracted from various literatures including Winkler et al. (1974) provides some of the major rootstocks and their specification.

Dog Ridge (V. champini) Description: A very vigorous variety; produce the most vigorous grafted vines of all rootstocks so far known. Roots and grafts well with great difficulty, lack compatibility, recommended for use with heavily producing wine and raisin grape varieties on light sandy soil where nematodes infestation may be heavy: induce zinc deficiency and bad setting of berriesin fertile soils, its resistance to nematodes is doubtful Growing tip: Felty, white with rose margin; brown stipules Young leaf: Upper surface downy, greenish-white, lower surfacc felty Growing tip: Felty, white with rose margin. Brown stipular Shoot: Light green, thick and leathery in stmcture, wavy edges, tufts of woolly hair between the veins 1 lowers: Female, small cluster with small, round, black, juicy berries Cane: Very vigorous, ribbed, with long internodes and long, pointed ovoid medium sized donnant buds, upper side covered with loose, woolly hair Teeth: Nearly flat Petiole sinus: Lyre shaped

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Rupestras St, George Description: Very vigorous rootstock, gral't well and form vigorous grafted vines, combined often with a very low fertility. Need deep soil, resist drought and poor soil: sensitive to poorly drained shallow soils; fairly resistant to lime induced chlorosis and salt; resistant to Phylo.xera and somehow resistant to nematodes. 1 jrowing rip: Glabrous on both sides, folded, flat Young leaf. Copper, very shiny Shoot: Erect in growth habit with numerous and vigorous secondary and tertiary laterals: intcrnodes violet-red, glabrous. ■'lowers'. Male-sterile • \me: Medium in length, very thick near die base ajid tapering rapidly towards the end: internodcs reddish- brown, very short (6-10 cm), round in cross- section with a small pith and narrow diaphragm; nodes fairly enlarged Feeth: Medium convex Petiole sinus Brass shaped

(Vitas berlandieri X V. riperia) . description: Roots easily and grafts well; when rooted ensures a good fruit set to advance maturity: tolerant to lime induced chlorosis and salt: suited to humid soil suitable for irrigated soil), not recommended for dry condition. Resistant to Phylloxera and nematodes. Growing tip: Downy white with rose margin oung leaf: Cobwebby, green Shoots: Horizontally spreading in growth habit, poorly developed laterals; internodes medium in length, violet-red -lowers: Male always sterile

'one: Long but slender, less vigorous; intcrnodes chocolate brown, ribbed, oval in cross-section with a small pith and narrow diaphragm Teeth: Convex nearly flat Petiole sinus Narrow “V” on young leaves, becomes an open “U” when adult

5 BB (V. berlandieri) Description: Roots easily and grafts well, not recommended for dry land condition, well suited to humid compact calcareous clay soil; resistant to nematodes and Phylloxera., very important variety in Europe, has shorter vegetative cycle Growing tip: Downy, white with rose margin, shepherd’s crook Young leaf: Cobwebby copper Shoot: Horizontally spreading in growth habit, laterals poorly developed; intcrnodes long green, striped red on the side of the sun; nodes not enlarged always pubescent Flowers: Female, cluster small with small round berries Cane: Very vigorous, long and thick; intcrnodes clear beige, ribbed, oval in cross-section with small pith and narrow diaphragm Teeth: Convex with wide to nearly flat Petiole sinus: Lyre-shaped

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41 B ( v in ife r a X American Hybrid) ( Vitis vinifera var. Chasselr X V itis Berladieri) Description: Root with difficulty; once rooted they graft easily; root well in soil very rich in lime; resistant to Phyloxera but susceptible to nematodes; not tolerant to salt: sensitive to excess humidity, the best all-purpose rootstock for table grapes in arid-and hot regions: provide longest productive life; susceptible to downy mildew.. Growing tip: Felty with white trace of rose on margin, flat open Young leaf: Downy, white indumenta, bronze blade Shoot: Semi-upright in growth habit with poorly developed laterals; intemodes medium in length, green with violet-red strips on the side of the sun. darkened at the nodes which are prominently enlarged. Flowers: Female , cluster small with round black berries Cane: Long and thick, silver grey-brown, ribbed, roundish in cross-section with a medium sized pith and very broad diaphragm ?eth: Convex wide Petiole sinus: Lyre-shaped

J IO R Richter n o (Berlandieri Resseguier # 2 X Rupestris martin) Description: It is among the principal rootstock varieties: vigorous rootstock; tends to delay maturity; resists lime; much more resistant to drought; grafts well but roots poorly Growing tip: Cobwebby with a red margin, reddish, flat Young leaf : Cobwebby, very bronze, shiny, bullate Shoot: Upright in growth habit, with numerous and vigorous laterals; intemodes long. deep, msty, wine red. covered with long, woolly threads in early stage of their development, nodes not enlarged Flowers: Male-hermaphrodite. usually sterile, but may be set fruit on very vigorous vine Cane: Long but fairly thin, glabrous, dull reddish chocolate to greyish-brown, ribbed, long intemode. buds small, done shaped Teeth: Wide convex Petiole sinus: An open “U”

3309 Coudere (Riparia tomenteus X Rupestris m artin) OR 3309 C Description: Roots easily and grafts readily, prefers stony soils, deep, well drained soil well supplied with moisture; sensitive to nematodes, moderately tolerant to lime soils, highly resistant to Phylloxera. Growing tip: Glabrous, shiny green Young leaf: Shiny, glabrous Shoot: Semi-upright in growth habit, with numerous and vigorous laterals; intemodes short, rusty, crimson red. nodes slightly enlarged, glabrous Flowers: Male/male hennaphrodite Cane: Medium vigorous, reddish-brown, streaked, round in cross-section with a fairly large pith and very narrow diaphragm Teeth: Bifurcated, very fine and short, reddish, glabrous Petiole sinus “V” shaped but an open “U” on adult leaves

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420 A [Berlandierz X Riparia gloire) Description: Docs 1101 root and graft easily, field grafting on to rooted one-year old vines give good result; somewhat resistant to nematodes, salt sensitive, not resistant to drought, early season variety in Europe (France), does well on fresh, deep, fertile soil Young: leaf: cobwebby, lightly bronze, very shiny Shoot: Horizontally spreading in growth habit, with properly developed laterals,; internodes long, reddish-brown on the side of the sun, darkened violet-red at the nodes, glabrous Flowers: Male always sterile Cane: Fairly dark chocolatc-brown, ribbed, oval in cross-section with a medium sized pith and fairly narrow diaphragm Teeth: Bifurcated, fine, reddish brown, glabrous Petiole sinus: Lyre-shaped

1.613 Couderc (Labrusca X riparia X vinifera) = 1613 C Description: Roots and grafts easily, resistant to nematodes, susceptible to Phylloxera, grafted vines grow with moderate growth in field soil well supplied with moisture, low tolerance to lime induccd chlorosis Growing tip: Fclty, white, shepherd’s crook Young leaf: Upper surface downy greenish-white, lower surface felty Shoot: Thick but not very long, horizontally spreading in growth habit, laterals poorly developed; intemodcs medium in length, pale green, nodes enlarged, covered with long loose woolly hairs. Flower: Female, small cluster with small, round, black, juicy berries Cane: Finely ribbed, clear brown, glabrous, long internodcs: small pointed buds Teeth: Large convex Petiole sinus: Lyre-shaped

140 Ru (Berlandieri Ressenguier # 2 X Rupestris du Lot)

Description: Very vigorous variety that has been used successfully in the dry, limy soils. It has good reaction to lime (20%). Roots are resistant to Phyloxerra. Field graft well Growing tip: Cobwebby with rose margin Young leaf: Pale, green, shiny Shoots: Ribbed, purplish, lightly glabrous with a few woolly-hair al the nodes; long intcrnodes. small, pointed buds Flower: Male always sterile Cane: Ribbed, dark mahogany red, glabrous with a few woolly hair al the node; long intcrnodes. small pointed buds Teeth: Medium convex Petiole sinus: Open, lyre -shaped

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References

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Webb, A.D., C.J. Muller. 1972. Volatile aroma compounds of wines and other fermented beverages. Advances in Applied Microbiology, 15:75-146. Weinberger, J.H and N.H. Loomis. 1962. A Rapid method for propagating grapevines on rootstocks. Agricultural Research Service. U.S. Department of Agriculture. ARS- W-2. Frresno. California. Whiting. J.R. and B.G. Morev. 1988. Drying of Carina grape. Aust. Dried Fruit News. NSI 15(3): 13 Whiting. J.R. 1982. Response of Zante grapevines to cane and harvest pruning. Amer. J. Enol. Vitic., 33: 185-90. William. R.N. and J. Granett. 1988. Phylloxera. In: Compendium of Grape Diseases. Pearson, R.C. and A.C. Goheen (eds). APS Press. The Amer. Phytopathology Society. St. paul, Minnesota, USA. Wilson. W.J. 1959. Analysis of the special distribution of foliage by two dimensional point quadrant, New Phytologist, 58:91-101. Winkler. A.J. 1968. Effect of vine spacing in an unirrigated vineyard on vine physiology, production and wine quality. Am. J. Enol. Vitic, 20:7-15. Winkler. A.J.. J.A. Cook, W.M. Kliewer and L.A. Lider. 1974. General Viticulture. Univ. California Press. Berkeley, 710 p. Yokoyama, V.Y. 1977. Frankliniella occidcntalis and scars on table grapes. Environ. Entomology, 6:25-29. Zelleke, A. and H. Duering. 1994. Evidence for tertiary bud within latent buds of'Mullcr- Thurga' grapevine. Vitis 33:96 Zelleke. Asfaw. 1971. Grapevine Production ( in Amharic). Bulletin; Ministry of Agriculture, Extension Department pp 18 Addis Ababa Zelleke. Asfaw and W.M. Kliewer. 1979. Influence of root temperature and rootstock on bud break, shoot growth and fruit maturity of Cabernet Sauvignon grapevines under controlled condition. Am. J. Enol. and Vitic. 30:312-317. Zelleke, Asfaw and W.M. Kliewer. 1980. Effect of root and air temperature, rootstock, and fertilization on growth and composition of Cabernet Sauvignon grapevines. Scientia Horticulturae, 13: 339-347. Zelleke. Asfaw and W.M. Kliewer. 1985. Influence of root temperature, rootstock, and fertilization on composition of Cabernet Sauvignon grapevines. Acta. Horticulturae, 158:255-263 Zelleke ,Asfaw. 1986. The effect of hydrogen cyanamide and benzyladenine on bud burst of cuttings of two Vitis species, Ethiop.J. gric. .Sci., 8(1): 11-17. Zelleke, Asfaw and W.M. Kliewer. 1989. The effects of hydrogen cyanamide on enhancing the time and amount of bud break in young grape vineyards Am. J Enol. and Vitic., 40(1):47-51. Zelleke, Asfaw. 2000. Production and Protection of the Grapevines (in Amharic). pp 41. EIAR, Addis Ababa Zelleke, Asfaw. 2004 . Temperature and gibbercllic acid effect on grow composition of Flame Seedless grapes (Accepted for publication in Ethiopian Journal of Crop Science Society 1(1): 76-82.

[161] Asfaw Zelleke

Glossary

Acid soil: A soil having a pH less than 7.0 Active ingredient: The chemical agent in a formulation that produces the desired effect Adjuvant: Materials combined with spray materials to act as wetting or spreading agents, stickers, penetrates, etc., to aid in the action of Lhe active ingredient. Adventitious roots: Roots formed in unusual places such as nodes of stems or cuttings. Adventitious bud: A bud developing in an unusual location. Shoots arising from such buds are termed adventurous shoots After-ripening: A period of chilling required by seeds and buds before germination will take place Alkali Soil: A soil wilh sufficient exchangeable sodium to interfere with the growth of the vine Ampelography: A compilation of detailed horticultural description of grape varieties Alkaline soil: A soil with a "basic" reaction, a pH greater than 7.0 Anthesis: The time of full bloom in a flower, just after the calyptras has fallen Anthocyanin: A natural pigment in the red, blue, purple and black grape varieties. The color is due to the five anthcyanidins (cyanidin, dephinidin, petunidin, peonidin and molvidin) that make up the basic pari of the grape pigment. Apex (apices): The tips of shoots or of lobes of the leaf Apical dominance: The inhibition of lateral bud growth by the apical meristem. The control is mediated by the production of hormones Apical meristem: Tissue at the apex of a root or stem where active cell division occurs Arid: A dry climate wiLh low rainfall and a high rate of evaporation Asexual propagation Propagation by plant parts other than seeds, such as budding, grafting, layering, and cuttings ^stringency: A puckery taste sensation caused mainly by tannin in the wine Auxins: Plant regulators that can stimulate cell division and enlargement in plants Bar: A unit of pressure equal to one mega dyne per square centimeter (about 750.076 mm of mercury) Easal bud: A small bud that lies al the base of a cane or spur as part of a whorl, which usually does not grow unless the distal buds fail to grow Eerry set: A period shortly after blooming when most of the flowers have fallen and lhe remaining pollinated ones begin to develop into berries Biological control: Control of pests bv disease-producing organisms, predators, and parasites

[162] The Grapevine

Bilateral cordon: Vine training in which the trunk is divided into two branches extended horizontally on a supporting wire. Often referred to as cordon training Blade: The expanded portion of a leaf Bleeding: The exudation of sap from cut canes; usually occurs toward end of dormant season Bloom: The delicate waxy or powdery substances on the surface of berries or buds Botrytis bunch rot: Bunches obviously infected with the fungus Botrytis cinerea Botrytis cinerea: a fungus that may infect the fruit following a period of free moisture and cool weather during the ripening period ; also called grey mold Bouquet: The perfume like scent, produced by esters and others, that in noted after uncorking and pouring wine Broadcast application: An application of spray or dust over an entire area, rather than only on rows, beds, or middles Bud: An undeveloped shoot usually protected by scales; tissues are mainly meristematic Bud break: An early stage of shoot development from a dormant bud when the now growth pushes aside the enclosing bud scales and show green leaf tissue Bud scales: Protective scale-like leaves of a bud during winter, covered with hairs and impregnated with suberin (see prophylls) Calcareous soil: A soil containing CaCOj or MgCC>3 that effervesces when treated with dilute HC1; usually has an alkaline reaction Callus: Parenchyma tissue, which grows over a wound or graft and protects it against drying or other injury Calyx: The external part of a flower consisting of sepals Calyptra: The fused petals of the grape that fall off the flower at an thesis Cambium: A very thin layer of undifferentiated meristematic tissue between the bark and wood Cane: A mature shoot of one-year wood, usually 12 tO 15 nodes length, retained al pruning Cap stem (pedicel): The stem of the individual flowers or fruit Carbohydrate: A compound produced by plants containing chemically bonded energy composed of carbon, oxygen, and hydrogen. Hydrogen and oxygen often have a ratio of 2:1 Carbon-to-nitrogen ratio: The relative proportion of carbon to nitrogen in the soil, organic matter, or plant tissue Catch wire: A wire, which serves as an attachment for developing grape shoots Certified planting stock: Grapevine propagation material certified free of known virus diseases by the California Department of Agriculture, under regulations of the Grapevine Certification and Registration program

[163]

■ Asfaw Zelleke

Chlorosis: Yellowing or blanching of green portions of a plant, particularly the leaves, which can result from nutrient deficiencies, disease, or other factors Done: A group of vines of a uniform type propagated vegetatively from an original mother vine Cobwebby: See under wooly Compatible chemicals: Materials that can be mixed together without adversely changing their effects on plants or pests Compatibility: Ability of the scion and stock to unite in grafting and form a strong union. Also refers to male and female nuclei that have capability to unite and form a fertilized egg that will grow to maturity Complete flower: A flower having sepals, petals, stamens, and a pistil or pistils Contact herbicide: A chemical lhal kills the portion of the weed or plant with which it comes in contact Corolla: The petals of a flower 'rop control: Managing the crop load by appropriate pruning and/or cluster thinning lo bring the crop and leaf surface into balance lo assure proper fruit maturity Cropping: Crop: The amount of fruit borne on the vines; Crop load: The mount of fruit borne on vines in relation to the vines' leaf surface; Over-crop: An imbalance of active leaf surface lo crop load; delays ripening and color development; Crop recovery: The crop produced by vines from regrowth following injury by early frost Crown suckering: The removal of unwanted shoot growth from the vine head and trunk while the shoots are slill young; often referred to as suckering Cutting: A severed portion of cane used for propagation Degrees Brix: A measure of the total soluble solid content of grapes, approximately the percentage of grape sugars in the juice Dentate: Toothed; usually with the teeth directed oulward as in a leaf Dioecious: Having the male (staminate) and female (pistillate) organs of the flower on separate plants Dormant: Plants, buds, or seeds that are not actively growing Downy: (See under woohj) Drying ralio: The pounds of fresh grapes required to make one pound or raisins Enology: The science and study of winemaking Enzyme: Organic catalysis composed of proteins lhal control most chemical reactions occurring in living cells Epinasly: Downward bending of leaves caused by some hormone sprays, water stress, etc ♦ Erosion: The wearing away of land surface, usually by running water or wind L

[164] The Grapevine

E thylene: A gas having a chemical structure of CH2=CHt, produced by most tissues in verv small amounts. It is often called a fruit- ripening hormone Eye: A compound bud of a grape Fascia lion: Flattening of the stem because of multiple buds growing in the same place Feeder roots: Fine roots and root branches with an unusually large absorbing area. Important in uptake of minerals and water by their root hairs Felty See under woolv Fermentation: The change of sugars into alcohol and carbon dioxide in the presence of yeast Fertility: A soil quality in which essential plant nutrients are provided in proper amounts and balance for optimum plant growth Fertilization: The fusion of one gamete with another to form a zygote in sexual reproduction. Also refers to application of fertilizers Flower buds: Buds containing undeveloped flowers; also referred to as fruit buds Foliage wire: (see Catch wire) Foliar feeding: Fertilization of a plant through Lhe surface of the leaves; usually accomplished by spraying Fruit: A mature ovary (berry) or cluster of mature ovaries Fruit-set: The stage of cluster development following the drop of impotent berries after bloom. The small, retained berries are said to be "set" Fungicide: A chemical used to control the infection and spread of fungi on crops Gibberellin(S): A plant growth regulator that promotes cell elongation and growth of shoots. Subscripts such as GA1, GA2 indicate specific analogues Girdling: The removal of a ring of bark from a shoot, cane, or trunk Glabrous Hairless Glucose: A simple sugar: one of the monosaccharide Grafting: The joining of a bud or other part of one vine to a portion of another so that their tissues unite Green-manure crop: A crop grown and plowed under to improve Lhe soil, especially by adding organic matter Head: The pressure due to the difference in elevation belween two points in a body or column of liquid, as a measure or the pressure or force causing water to flow. Sometimes referred to as pressure head. In addition, that portion of a trunk where arms or cordons originate ^ Headland: Unplowed land at the1 ends of the rows or near a fence; often used for turning space for various equipment Herbicide: Any chemical used to kill plants; some are selective and kill only J certain plants Herbaceous: Green soft tissue; not woody

[165] Asfaw Zelleke

Hermaphrodite: A flower with both male (stamen) and female (pistil) parts Hirsute: Pubescent, having rather coarse or stiff hairs Hormone: Plant hormones are regulators produced by plants Lhal, in low concentrations, regulate physiological plant processes. They usually move from a site of production to a site of action Host: Any plant or animal attacked by a parasite or predator Hybrid: It is practice of crossing species imperfect flowers: Flowers in which either function able stamens or pistils are present, but not both incompatibility: Inability of sex cells to form a fertilized egg that will grow and mature. Failure of the scion and stock to unite and form a union that will continue lo grow. Also refers to agricultural chemicals that cannot be mixed or used together because of undesirable reactions Incomplete flower: A flower that does not have all four floral organs Indexing: Determination of the presence of disease, such as a virus, in a vine by removing buds or other parts and grafting them into a readily susceptible variety that exhibits symptoms of the virus Indigenous: A vine or plant native to the region Indoleacetic acid: Naturally occurring auxin-type plant regulator, which causes many growth responses Indumenl: Hairiness Inflorescence: The flowering cluster of the grapevine Infiltration rate: The rate of downward water movement from the soil surface into the soil Internode: That portion of a shoot or cane between two adjacent nodes Irrigation: The artificial application of water to soil to supply essential for plant growth * Land leveling: Removing soil from a high place and filling in a low place lo level the land Lateral: A branch of the main axis or the cluster; also a shoot arising from the main shoot Latent bud: A dormant bud, usually hidden, which is over a year old and may remain dormant indefinitely Leach: The process of removal of soluble material by the passage of water through the soil; it is a primary step in reclamation of a saline soil Leaf bud: A bud, which develops into a stem, bearing leaves but no flower clusters l,eaf scar: The scar left on the stem after a leaf falls l^es: The sediment at the bottom of a wine cask, consisting mainly of tartaric acid/ tartarale Lenticel: A pore like, slightly raised spot on pedicels and grape berries ^ Light saturation: The light intensity at which an increase in light does not result in an increase in the rate of photosynthesis / Maturity: Stage of fruit development when it has reached the maximum quality for its intended purpose

[166] The Grapevine

Meristemalic: A region of the plant where rapid cell division takes place Metabolism: The sum of processes by which food is manufactured and broken down for energy gain lllerandage: The condition shown bv clusters that is too loose because of poor fruit set and too many shot berries Monoecious: Having male and female flowers on the same plant > lulch: Materials placed on the soil surface or mixed in Lhe soil, such as straw, to promote moisture retention, temperature control, provide cleaner fruit (as in strawberries), weed control and, il the mulch is plant malerial, to supply nutrients as Lhe mulch decomposes Mutation: Genetic change in a mother plant or stock that may influence the character of Lhe offspring, buds, or cuttings removed from Lhe plant Mycelium: A group or mass of fungus filaments Mycorrhi/a: Symbiotic association of Lhe mycelium or hyphae of certain fungi with Lhe rooLs of the plant Must: Crushed berries and juice Mematode: A very small parasitic worm that lives in or on grape roots Noble rot: A fungus thaL develops on the skins of ripe grapes in certain areas. The fungus penetrates the skin of the grape without breaking it, so the grape can wither wilhouL spoiling. Such grapes have very high sugar contenl Node: The area on a slem from which shoots develop Nonsaline-alkali soil A soil Lhal contains sufficient exchangeable sodium to interfere with the growth of Lhe vine, but does noL contain appreciable quantities of soluble salts Over cropping: Production of more crop than the vine can bring to maturity al normal harvest time. 11 can resull from light pruning, water slress, insects, or disease Parasite: An organism that lives on or in the body of another organism and obtains food from it Pedicel: The stalk of one flower or berry in a cluster (Fig. 1.4) Peduncle: The (. luster stem, which is usually refers to stem, from the point of atlachmenL Lo Lhe shoot to the first lateral branch on the cluster Perfect flower: A flower having both stamens and pistil Petiole: The leaf stalk aLLaching the leaf blade to Lhe shooL pH: Refers to degree of acidify or alkalinity as a scale of numbers from 1 (very acid) lo 14 (very alkaline). pH 7.0 is neulral, representing the reciprocal of the hydrogen ion concentration and expressed in gram atoms per liter of a solution Phloem: Region of tissue in the plant composed of sieve Lubes and parenchyma, which translocale food materials elaborated by lhe leaves Photosynthesis: The process by which carbon dioxide and water are incorporated into carbohydrates; solar energy is the source for this process

[167] Asfaw Zelleke

Phylloxera: A small, yellowish aphid like insect that attacks roots and/or leaves, but does most damage to the root system Phytotoxic: Causing injury or death of plants Pilh: The female part of the flower, consisting of a stigma, a style, and an ovary distillate flower: A flower having a pistil but lacking stamens Dlant propagation: Controlled reproduction of vines and other plants by humans, to perpetuate selected individuals or groups of plants of special value to him /her ^lant regulator: Organic compounds other than nutrients, which, in small amounts, promote, inhibit, or otherwise modify any physiological plant process. The five main groups are auxins, gibberellins, cytokinins, inhibitors, and ethylene Plaque: A flattened, visible group of mycelium strands, often arranged in a fan shape. Pollen Ograins: The microspores and developing male gametophytes found in the anthers Pollination: The transfer of pollen from the anther to the stigma Pomace: Crushed grapes after the juice has been extracted Porosity: Refers to pore space. It is the ratio of the volume of air- and water-filled space to the total volume of soil plus water and air Pori: A very sweet, full-bodied, rich dessert wine ppm: Parts per million. The concentration of a material expressed as the number of units per million units. It is the same as milligram per liter Premium-variety: A grape variety that produces a wine of high quality and imparts distinctive characteristics lo its wines, e.g., Chenin blanc Prophylls: Scale-like leaves produced before foliage leaves borne on the first and second node of a bud. Also referred to as bud scales Primordia: Regions in plants, such as the tips of stems and roots, where plant structures are initiated Pruning: Cane: A pruning method in which canes are retained as the fruiting units usually 4 to 12 nodes long; Spur: A pruning unit whereby spurs are retained as fruiting units (lone to two nodes long) Pubescent: Covered with hairs nearly perpendicular to the plant surface and commonly referred to as bristly or velvety Quarantine: A legal action preventing the sale or shipment of reproductive parts, such as seeds, cuttings, and rooting, to prevent the spread and infestation of a disease such as a virus, or of an insect pest Quiescence: Period of none visible growth controlled by external factors. Growth will proceed under favorable environmental conditions Racking: The pumping out or siphoning of wine from the sediment (less) Respiration: The oxidation of food materials by plants, and the release of energy during which oxygen is absorbed and carbon dioxide is released

[168] The Grapevine

Rest: Period of none visible growth controlled by internal factors. Growth will not occur even under favorable environmental conditions Ringing: (See Girdling) Risers: Pipes used in sprinkler irrigation that support the sprinkler heads above the level of the foliage Rootstock: Stock material to which other varieties of grapes are grafted to produce a commercially acceptable vine. Some rootstock varieties are less susceptible to injury by root parasites, such as Phylloxera and nematodes, than are the roots of the scion variety Rosette: Leaves with a bunched appearance caused by development of short internodes Rugose: Wrinkled or uneven Saline soil: A none alkali soil containing sufficient soluble salts Lo injure the crop Sap wood: OuLer, younger, more porous region of the vine beneath the bark where active growth occurs Scion: The plant part that is grafted or budded onto Lhe stock Seed: A fertilized and ripened ovule containing an embryo, which can develop into an individual by germination Selective herbicide: A chemical that can kill some weeds but is only slightly or non- toxic to lhe crop plant Self-pollinated: Pollen placed on the stigma of the same plant or a plant identical to it. Sepal: One of the modified leaves of Lhe calyx; the outermosL floral organ Serrations: Teeth like indentations at the margin of a leaf Sexual reproduction: Reproduction by the fusion of gametes Shoot: Current season's stem growth that bears leaves and buds Shot berry: Very small berries that fail to develop to normal size; usually seed less Shouldered cluster: The basal laterals are larger than the other laterals Siphon: A hose for transferring liquids from a higher elevation to a lower one Sod culture: Type of management in which a permanent perennial groundcover is kept at all times, and is usually mowed periodically during the growing season Sodic soil Soil with enough sodium attached Lo clay particles to interfere with crop growth Soil structure: The aggregate arrangement of individual soil particles Soil texture: The relative proportion of the percentage of sand, silt, or clay particles in a soil Sparkling wines: Wines lhal effervesce when opened Sperm: The male gamete Spreading growth: The growth habit of certain varieties in which shoots extend upward and outward from the vines trunk Sprinkler irrigation: Irrigation by means of surface pipes and sprinkler heads

[1691 Asfaw Zelleke

Spur: A shorl fruiting unit of one-year growth, usually consisting of one or two nodes; retained al pruning Standard variety: a grape variety such as Chenin blanc lhal does not imparl a distinctive character to its wines; usually blended for generic wines in some countries (Gilifornia where Brandy is a good example) Stamen: The pollen-producing organ of a flower, consisting of the anther and a filament Staminate flower: A flower with stamens but no pistil Stenospermocarpy: The phenomenon in which fertilization occurs and seeds are produced, but soon abort. Mature berries contain only rudimentary seeds, as in Thompson Seedless and Black Monika Stigma: The upper surface of Lhe pistil, where the pollen grain is rec eived and germination takes place Stipules: Small scale like leaves at the base of the petiole which fall off early in the season. Stock: The stem or root onto which the scion is grafted Stomata: A pore in the epidermis of a leaf or young stem surrounded by two guard cells Stratification: The subjecting of seeds lo an after-ripening period lo terminate the rest period. The seeds are usually exposed to low temperatures under moist but well-aerated conditions Style: The portion of the pistil between the stigma and the ovary Slylar scar: A small corky area remaining at the apex of a berry after the style drys and falls off following blossoming Sucker: A shoot arising from lhe lower part of the trunk, or from the part of Lhe stem below ground Sunscald: Injury lo outer tissue due lo excess sun heat, as on berries Surfactant: A chemical, which modifies the surface tension of spray droplets, causing them lo spread out on a leaf and form a thin film Systemic: An insecticide absorbed by plants and translocated throughout, which kills certain insec ts Systemic herbicide: A compound, which is translocated throughout a plant and can readily injure or kill the' plant annin: A component of wine lhal gives it an astringent taste Temperature inversion: A meteorological phenomenon whereby the air temperature becomes warmer, with increasing altitude, instead of becoming cooler as is normal Tendril: A slender structure on a shoot lhal can coil around an object and help support lhe shoot Tensiometer: An instrument used lo measure water tension in the soil Tolerance: Amount of toxic residue allowable by law in or on edible substances Tomentum: Composed of densely matted, liny epidermal haired; pubescence Trailing growth: The growth habil of certain varieties in which shoots tend to hang or drop

[170] The Grapevine

Res I: Period of none visible growth controlled by internal factors. Growth will not occur even under favorable environmental conditions Ringing: (Sec Girdling) Risers: Pipes used in sprinkler irrigation that support Lhe sprinkler heads above the level of Lhe foliage t Rootstock: Slock material Lo which other varieties of grapes are grafted to produce a commercially acceptable vine. Some rootstock varieties are less susceptible Lo injury by root parasites, such as Phylloxera and nematodes, than are Lhe roots of Lhe scion variely Rosette: Leaves wrilh a bunched appearance caused by development of short internodes Rugose: Wrinkled or uneven Saline soil: A none alkali soil containing sufficient soluble salts Lo injure Lhe crop Sap wood: Outer, younger, more porous region of Lhe vine beneath Lhe bark where active growth occurs Scion: The plant part that is grafted or budded onto the slock Seed: A fertilized and ripened ovule containing an embryo, which can develop into an individual by germination Selective herbicide: A chemical that can kill some weeds but is only slighLly or non­ toxic to Lhe crop plant Self-pollinated: Pollen placed on the stigma of the same plant or a plant identical to it. Sepal: One of the modified leaves of the calyx; the outermost floral organ Serrations: Teeth like indentations at the margin of a leaf Sexual reproduction: Reproduction by the fusion of gametes Shoot: Current season's sLem grow I h Lhal bears leaves and buds Shot berry: Very small berries that fail to develop lo normal size; usually seed less Shouldered cluster: The basal laterals are larger than lhe other laterals Siphon: A hose for transferring liquids from a higher elevation to a lower one Sod culture: Type of management in which a permanent perennial groundcover is kepi at all limes, and is usually mowed periodically during lhe growing season Sodic soil Soil with enough sodium attached lo clay particles lo interfere with crop growth Soil structure: The aggregate arrangement of individual soil particles Soil texture: The relative proportion of the percentage of sand, silt, or clay particles in a soil Sparkling wines: Wines that effervesce when opened Sperm: The male gamete S p re a d i n g gr o w I h: The growth habit of certain varieties in which shoots extend upward and outward from the vines trunk Sprinkler irrigation: Irrigation by means of surface pipes and sprinkler heads

[169] Asfaw Zelleke

Spur: A short fruiting unit of one-year growth, usually consisting of one or two nodes; retained at pruning Standard variety: a grape variety such as Chenin blanc lhal does not imparl a distinctive character to its wines; usually blended for generic wines in some country's (California where Brandy is a good example) Stamen: The pollen-producing organ of a flower, consisting of the anther and a filament Staminate flower: A flower with stamens but no pistil Stenospermocarpy: The phenomenon in which fertilization occurs and seeds are produced, but soon abort. Mature berries contain only rudimentary seeds, as in Thompson Seedless and Black Monika Stigma: The upper surface of the pistil, where the pollen grain is received and germination Lakes place Stipules: Small scale like loaves at the base of the petiole which fall off early in the season. Bloc k: The stem or root onto which the scion is grafted Stomata: A pore in the epidermis of a leaf or young stem surrounded by two guard cells Stratification: The subjecting of seeds Lo an after-ripening period to terminate the rest period. The seeds are usually exposed to low temperatures under moist but well-aerated conditions Style: The portion of the pistil between lhe stigma and the ovary Stylar scar: A small corky area remaining al the apex of a berry after lhe style drys and falls off following blossoming Sucker: A shoot arising from the lower pari of the trunk, or from the part of the stem below ground Sunscald: Injury to outer tissue1 due to ext css sun heat, as on berries Surfactant: A chemical, which modifies the surface tension of spray droplets, causing them to spread out on a loaf and form a thin film Systemic: An insecticide absorbed by plants and translocated throughout, which kills certain insects Systemic herbicide: A compound, whii h is translocated throughout a plant and can readily injure or kill the plant Tannin: A component of wine that gives it an astringent taste Temperature inversion: A meteorological phenomenon whereby the air temperature becomes warmer, with increasing altitude, instead of becoming cooler as is normal Tendril: A slender structure on a shoot that can coil around an object and help support the shoot Tensiometer: An instrument used to measure water tension in lhe soil Tolerance: AmounL of toxic residue allowable by law in or on edible substances Tomentum: Composed of densely matted, liny epidermal haired; pubescence Trailing growth: The growth habit of certain varieties in which shoots tend to hang or drop

[170] The Grapevine

Translocation: Movement of water, nutrients, chemicals, or elaborated food materials within a plant Transpiration: Water loss by evaporation from the leaf surface and through the stomata Trunk: The main stem or body of a vine between the roots and the place where the trunk divides lo form branches Tureidity:o Pressure caused by fluids in the cell that press against the cell and distend it. Uracil; a nitrogen base lhal is located in lhe RNA with a pyrimidine ring structure Varietal wine: A wine named after a grape variety. At least 51 percent of the wine must be from the named variety, and the typical varietals flavor must be present Variety: A group of closely related plants of common origin that have characteristics not sufficiently different to form separate species Varietal character: Distinctive characteristics of certain garpes and wines Lhal make them recognizable; such as Cabernet aroma. Vegetative propagation: Plant reproduction, using vegetative organs such as cuttings Verasion: The stage of development when berries begin to soften, increase in sugar: acid ratio and change in color of pigmented varieties Vigorous vines: Vines wilh shoots that grow rapidly and produce much growth Bilateral cordon: A system of vine training that divides the trunk into Iwo permanent branches, each extending in opposite directions down lhe vine row and horizontally supported on a trellis wire; commonly referred to as cordon training. The vines are sour pruned Vintner: A winemaker Viticulture: The science or study of vine production and natural drying of raisins Water berries: A grape disorder characterized by watery berries lhal fail to ripen properly Water-holding capacity: (See Field capacity) Waterlogged: Soil wilh poor drainage that lacks sufficient oxygen for proper root functioning Waler sprouts: Rapidly growing shoots arising from latenl buds on branches or trunks *Veliable powder: Solid formulation that forms a suspension when added lo water Wild vine: A vine that grows in the wild Wing: A well-developed basal cluster laterals that projects and is separated from lhe main body of the cluster the plant surface Lhal its own color can not lo be distinguished Wooly: Long intertwining hairs spread out over lhe plal surface; expressed in various forms, a) felly:- the hairs are very close togelher and so completely cover lhe plant surface that its own color cannot be distinguished ; b) downy:- the density is light

[171] Asfaw Zelleke

that the color of the plant surface shows through; c) cobweby:- few hairs are spread out as in a spider's web Xylem The woody portion of conducting tissue whose function is Lhe conduction of water and minerals Kygote: A fertilized egg; cell arising from lhe fusion of Lwo gametes

[172] The Grapevine Index beetles • 104 bench grafting • 29, 33, 34 A Benlatc • 98 Benomyl • 98 berlandieri - 3, 148 Abiotic Stress • 95 berries • 135, 144, 148, 149, 155, 165, 167. 170 abscission ■ 49, 100 berry shatter • 122 absorption • 10, 17, 20, 54. 86 berry size • 25, 64. 121, 122. 123. 133 acid soils • 78, 79, 83 beny' softening • 25, 89 active transport ■ 20 Berry thinning 121 ageing. • 99 berry volume • 26 agro-ccological 104. 108, 138 beverages • 136 alcohol • 113, 114, 115. 165 Bifurcated • 149, 150 alkali salts ■ 48 biological control • 99 alkali soils • 48, 93 biomass • 68 alkaline oil emersion 129, 130 Biotic Stress ■ 96 aluminum phosphate • 68 birds 110 aluminum. ■ 48 Black Corinth • 23. 146 American species ■ 3, 4 Black Hamburg ■ 140 amino acids • 26, 70, 114 bloom 18. 23, 68, 77, 81. 83, 84. 86. 96, 118, ammonia • 56. 71, 74 122. 123, 124, 133, 142, 144. 162. 165 ammoniacal fertilizers • 73, 74 Bordeaux-mixture • 99 Ammonium • 26. 73 boron ■ 48, 69, 70, 82, 83, 84, 87, 90, 9.3, 105 ammonium nitrate -31, 55, 56 Botrytis ■ 34, 96, 99. 100. 124. 126, 143, 145, ampelography ■ See Classification 147, 163 antelopes ■ 108, 109, 110 Brix 131 anthcsis • 13, 118, 122, 123, 163 browning • 126, 127, 128 anthocianin ■ 65 bud ■ 10, 12, 13, 14, 22, 23, 28, 33, 38, 39, 40, Anthracnose 101 57, 58, 63, 66, 95. 165, 167, 169 aphids • 104 bud break • 21, 23, 72, 75 apical dominance • 48 bud rest • 6 arbor training • 62 bud sports 111 arginine ■ 65, 71 bud stick ■ 33, 38, 39 arm • 12 budding • 27. 29. 32, 33, 36. 40, 102, 162 aroma -7, 18. 115 budding knife • 33 Aroma 115 budding tape • 33 aromatic substances 115 budding-knile ■ 39 Ascorbic aid 117 bunch rot • 16, 60. 96, 98, 99. 100, 121, 163 aseptic culture • 42 bunches • 55, 64, 99, 10.3, 116, 119, 120. 121, asexual • 27, 30 123, 124, 125, 132 Asia Minor • 1 bundles • 28. 30 auxin 23, 46, 80, 166 burning • 77 Awash Winery • 7

11 c Cabernet Sauvignon • 8. 143 bacteria • 70, 73, 79, 117 calcareous soil - 147 bacterial contamination ■ 99 calcium ■ 1, 69, 70. 73, 75, 79, 80, 93 bacterial disease ■ 29, 96, 102 calcium carbonate ■ 48 baits ■ 109, 110 Calcium nitrate • 73 Barbara • 78, 92 callusing ■ 29, 30, 32, 33, 34 4- basin irrigation ■ 55 callusing bed • 30 Bayleton wp ■ .31 callusing room ■ 34

[173] Asfaw Zelleke

calyptra 23 cover crops - 54. 55, 56, 74, 119 cambia • 33 crispness 64, 115 cambium layers • 34, 36, 37 crop 1. 23, 48, 49. 60, 63, 64, 66, 67. 70, 72. canary seeds 110 74, 76, 77, 83, 96, 97. 99, 100, 101, 102, candicans • 3 166, 168, 170 cane - 12, 14.22, 27,41,50, 58,62,63,81.91. Crop load 164 104, 120, 122, 144, 145. 146. 164. 165 crop thinning 121 cane pruning 60, 128. 142 crown gall • 102 canning 4, 136 Cultivar 4, 7 canning grapes ■ 4 cultivation 6, 7, 8. 9, 13, 52, 54, 57, 95 Cannonano 140 cultural practices • 9. 57, 63, 64. 102, 110 canopy • 57, 62, 63, 64. 65, 116 cupric hydroxide • 99 | Canopy density 63 curing 132 Canopy management - 64 Curing -132 canopy microclimate 62, 63. 64 curling ■ 77 captan • 99 cutworms 105 carbohydrate 19, 22, 23, 29, 66, 71, 82. 96 cytokinins 20, 23 carbohydrate/nitrogen ratio 22 carbon dioxide • 114, 118, 165, 169 carbonate ■ 74 1) Cardinal • 118, 144 Carignan • 92 earner system - 20 dagger nematode 107 caterpillar • 104 DBCP 107 caustic soda 130. 131 Debre Zeit 2, 7, 23, 54, 99, 138 champini ■ 3, 147 decay • 5,36, 126, 133 Chardonnay 4,8 deciduous - 75 Chemical treatments 122, 123 Deficiency 75. 76, 79. 83. 85, 86 Chenin blanc • 8, 113, 139. 169. 170 deficiency symptom ■ 55 Cherry red 144 defoliation 6,21, 153 chilling • 95 degree Brix - 7, 118 chimeras 111 degree-days • 7, 47 chimeric vines 111 dehydration 5, 131 chinosol 29. 32, 33 denitrification • 70, 73, 79 chip • 33, 38, 39 desiccation 29, 33, 54. 126 chip budding • 33, 38 dessert wine 113 chlorophyll - 18, 19, 25, 70. 71, 79. 80, 85, 86, dessert-wine 113 87, 111 developing bud 95, 96 Chloropyriphan 106 developing fruit 96 chlorosis ■ 79, 83, 84, 85, 86, 148, 150 dextrose 1 citrus nematode • 106, 107 diagnosis - 81, 85, 87 Cleft grafting • 36 diammonium phosphate • 56, 75 Climate ■ 6, 7, 26, 47. 63, 101, 128, 162 diaphragm 3. 148, 149, 150 Climate • 47 differentiation 65. 82, 95 Cluster thinning 121 dip emulsion 131 gold room • 29, 30, 31, 33, 124, 127 Dipping 131 color 115, 118, 119. 120, 123, 130, 133, 138, Dire Dawa • 54 162, 164, 172 disbudded 32, 33 compact bunches 121 Discontinuous -63, 139, 140, 141, 144, 145, concentration gradient • 20 146, 147 condensation • 89, 127 disease • 62, 64, 97. 100, 101, 102, 103, 104, cooked” flavor - 5 120, 123, 163, 164, 166, 169 cooking soda • 130 disease pressure • 97 copper oxychloride • 99 disorder appearance ■ 89 Cordon training 58, 61 Dithane 99 corky bark ■ 104 doanima • 3 Dog Ridge • 147

[174] The Grapevine

Dormancy • 2 i ferrous ion - 85 dormant period - 6. 21. 28, 48, 71. 72, 77 ferrous phosphate • 68 double sigmoid curve • 25 fertilization • 13, 55 downy mildew -31, 96, 98, 99. 101. 140. 146. fertilizers • 54, 56. 67. 69, 72, 73. 74, 76, 78, 80, 149 84, 87, 165 drip irrigation • 55 FIELD BUDDING ■ 34 dry table wines 115 field capacity • 31 dry weight ■ 18, 19. 25, 68. 70, 74, 76, 134. 152 Field packing • 124 drying "so, 54, 102, 128, 129, 130, 131, 132. FIELD PROPAGATION ■ 34 ' 133, 134, 136, 163 Flame Tokay • 144 drying oil 131 flavor ■ 5, 9,' 16, 18, 26, 114. 1 16. 118, 120. 123. drying ratio • 134 128, 132. 136 DTPA • 86 Hood irrigation ■ 105 dusting, • 57 Hooding ■ 109 flower : 12, 13, 23. 81. 95, 162, 163. 164. 166, 167.170 E flower bud • 23 flower cluster -3, 13 flower formation • 22 HDD! IA • 86 flower induction • 96 electrical conductivity • 88 Hying moths • 105 elongate bunches • 122 foliage manipulation • 64 embryo • 23, 25, 45. 170 foliar symptoms • 78 Emperor • 92, 119, 144 foot-candles • 22 endogenous factors • 21 forked tendrils • 3 endosperm ■ 23 French Colombard • 8, 92, 141 energy ■ ii. 18, 19, 65. 69, 75, 163, 167, 169 fresh grapes • ii, 4. 5. 8, 133 environmental factors • 19, 21. 97, 113 fresh-tables 113 enzymatic activity 117 frost • 23, 47, 50, 164 enzyme ■ 18, 69, 85, 117 fructose • 1. 26 eradicant spray • 98 fruit -7, 12, 13, 16, 23, 27, 49, 57, 59, 62. 64, erythorbic acid 118 65, 66, 67. 70, 71, 76. 77, 80, 82, 83, 95, 96, essential nutrients • 48 97, 98, 100, 103, 105, 111, 114, 1 17, 1 18, Ethephon 123 119. 121, 122, 124, 125, 133, 136, 148, 155. Ethiopia 1.4, 9, 30, 31.48,51, 57. 59. 67, 69. 163, 165, 167 75,87,98, 100, 102, 108, 117 fruit bud • 22, 23, 65 ethyl ester 131 fruit coloration • 65 ethylene • 23. 25 fruit flies • 105 etiolation • 34 Fruit thinning 121 Euvitis • 3 fruitful buds - 22, 23 exchangeable Na ■ 93 fruiting canes • 62, 63 exchangeable sodium percentage ■ 88 Fruiting varieties ■ 138 exogenous factors • 21 Fruiting Varieties ■ 138 fruiting variety • 33, 35, 147 full bloom ■ 89, 90 F full crop • 60 fumigant 30, 107 fan leaf • 103 Fumigation ■ 30, 126 fasciations 111 fungal disease • 98, 124 Fe chlorosis • 85 fungicides. • 97 feeder roots • 10, 107 fungus -62,97,98,99, 100, 101, 1 13, 127, 163, felty • 139. 142. 143, 145, 150, 172 167 Fenamiphos • 32 furrow irrigation • 55 fermentable sugars 113 Furrow irrigation -31, 120 fermentation -26. 113. 114, 115 Ferro magnesia rocks. ■ 86

[175] Asfaw Zelleke

G H gallicicolc 106 Hand Harvesting 128 galls 102, 107 Hardwood cuttings • 27 Camay - 78 harvest time ■ 23, 89, 100, 168 gamete: male and female • 23. 165 harvesting 64, 66, 96. 102, 114. 117, 119, 120, GBM • 141, 143 128,133 gelatinous matrix • 107 hazardous 49, 108 genetic variation • 27 head trained • 50. 58, 145 gemiplasm • 42 Head-training • 60 gibberellins ■ 20, 23, 122 heat summation • 7, 96. 128 girdling -23, 122, 146 heavy cropping • 84 Glabrous 139, 144, 148, 149, 165 heavy soils - 85 glasshouse • 34 herbaceous■3 glutamine -21. 26, 71 herbicides 31, 54 glycosides 115 highlands • 32. 48, 58. 91 golden yellow - 142 Hill reaction 18,86 golden yellow 129, 130, 142, 145 honey combed • 106 golden-bleached • 129 hormones • See dormancy Grading ■ 32 I lot water treatment ■ 29 gtaft • 33, 34, 35, 36, 37,46, 52, 148, 150, 163 House packing • 125 gtall union • 28 humidity • 7, 33, 46, 63, 97, 100, 104, 116, 126. grafting • 27, 30, 32, 33, 34, 35, 36, 37, 39, 45, 127, 128, 149 46, 102, 150, 162, 164, 166 1 lungary 100 grafting wax • 34, 36 hybrids • 3 grape -4, 5, 9, 35, 43, 48, 51, 71. 78, 87, 88, 90, hydrogen cyanamide ■ 123 95, 96, 98,99, 100, 101. 102. 104, 107. 126. 128, 133, 136, 139, 141, 142, 143, 147, 153, 162, 163, 164. 165, 167 / grape fruit - 113 grape hopper 104 illumination ■ 22 grape juice • 26, 114, 136 immature inflorescence 100 grape pest • 98 immobilization • 85 grape varieties • 72, 113 indolebutyric acid • 32, 46 grape-must • 136 infertility. • 30 grapes • 4, 9, 13, 47, 48, 50, 63, 67, 80, 87, 97, infestation - 5. 100, 105, 107, 109, 134, 169 100, 102, 105, 107,108, 113, 114.115. 117. inflorescence 3, 23, 95 118, 119, 120, 123,124, 125, 133,134. 136, inflorescence thinning 121 138, 154. 156, 159,164, 165, 167,168 inherent vigor • 71 grapevine 16, 38, 41, 43, 46, 48, 51, 54. 55. inhibitors -21, 23, 46 63. 65, 67, 68. 69, 70, 75, 76. 78, 80. 82. 83, insect - 5, 24, 30, 31, 34, 35, 100. 104, 105, 118, 87,89,95,97, 101, 103, 104. 106, 107. 108, 119, 134, 169 111, 113, 138, 152, 166, See insect pests • 30 grasshopper ■ 104 in tern odes 22. 27. 50, 80, 83, 103. 105, 120, gray mould ■ 99 148, 149, 150, 169 Grenache blanche • 139 inter-veinal 85, 103 Grenache noir • 140 IPM • 105 growth cycle • See Phenology iron 1,69,70, 75, 76, 86,93 growth hormones • 23 iron chelates • 85 growth period See phenology irrigation • 50, 51, 52, 53, 54, 55, 57, 58, 66, 70, Growth regulators 46 73, 78,81,93,94. 105, 108. 109, 114,118, guttation • 20 119, 120, 128. 169, 170 gypsum • 88, 93, 94 Irrigation 31 irrigation water 31, 73

[176] The Grapevine

J M judicious application • 55 macronutrients • 70, 75 juice • 1, 136, 164, 167, 168 magnesium 69. 70, 78, 79, 80. 90, 93 Juice Grapes • 5 magnesium sulphate • 79 mahogany • 139, 144, 150 Malaga 145 A Malate • 26, 114 malathion ■ 105 Malbec ■ 78 K • 21. 26, 27, 68, 76. 77, 78. 79, 90, 91, I 14, male gametes • 23 i 19 malformation -86, 103, 107 Karathane • 98 malic acid • 1, 21, 26 mammals • 108 management ■ 2, 25, 54, 62, 63, 65, 67, 98, 101. L 105, 108, 109, 110. 113, 152, 170 mancozeb ■ 99 labor. ■ 54 maneb • 99 labrusca • 3 manganese • 69. 70, 86, 87, 90 larvae ■ 105 manganous ion ■ 86 laterals ■ 56, 58. 62, 64, 148, 149, 150. 170. 172 manure • 49, 52. 74, 88, 166 lattice structure - 85 marketing • 96, 127, 135 layering • 27. 41, 162 marmalades • 136 leaf■ 13 maturation • 25, 86, 153 leaf area • 63 maturity indices 115 leaf blades • 68, 76, 89. 90 maturity standards • 123 leaf bum • 77, 91 Mechanical harvester • 128 leaf galls • 106 mechanical harvesting 117 leaf layer • 63 mechanical injuries -71, 106 leaf petioles ■ 90 Merlot 143 leaf primordial ■ 45 mesh-wire • 109 leaf roll 103 metabisulfite • 117, 127 leafroller ■ 104 metabolism ■ 18. 25, 26, 29, 82 leaf tissues • 85 methyl bromide • 107 leafhoppers • 104 metiram • 99 leaves ■ 12, 21, 63, 64, 65, 66, 68. 70, 71, 77, micronutrients • 70, 80, 82, 86, 87, 92 79, 80, 81, 82, 83, 85, 86, 87, 97, 98, 101, microorganisms • 70 103, 104, 105, 106, 111, 141, 142, 143, 144, Micropropagation • 42 147,163, 164, 165,168,169, 170 micropropagtion • 41 legumes • 74 migration habits - 105 leguminous plants - 70 mildew losses ■ 98 lenticels ■ 3 millerandage • 23 levulose • 1 mineralization ■ 70, 79 I ifting • 32 minerals • 1, 11, 70, 76, 80, 82 light ■ 19 minor elements • 70 Light intensity ■ 19, 22, 96 moisture ■ 5, 73, 74, 77, 89, 100, 105, 126, 129, lime-induced chlorosis • 85 131, 132, 133, 134, 149, 150, 163 limestone • 78, 79 moisture status ■ 55 limy soils ■ 150 moisture stress • 77, 105, 120 lincecumii • 3 mold • 133 Lyre-shaped • 141, 142, 143, 144, 145, 146, mole rats • 108, 109 147,149,150 molybdenum • 69, 70 monoterpenes • 65 monticola • 3 morphology • 25

[177] Asfaw Zelleke

Morphology 10 own rooted 28. 30, 46, 52 mottling • 80, 103 oxidation 19, 99, 117, 118, 134, 169 muratc of potash • 76 Muscadinia - 3 Muscat flavor • 140 P muscat flavour 142 Muscat Hamburg • 146 packing 54, 124, 125, 126, 132 Muscat of Alexandria 147 packing materials • 124 must -4, 61,81, 107, 110, 114, 115 packing styles • 125 mutation • 111, 112 parasitic nematodes 106 parent materials 48 parthenocarpic • 23, 25, 122 N passive movement ■ 20 pastries • 135, 136 natural enemies • 104, 105, 109 pathogen • 34, 97, 101, 102 natural thinning • 23 peat • 33, 36 necrotic spots • 101, 107 pectin 26 nematocides • 107 peduncle • See fruit nematodes -32,35, 49, 71, 102, 104, 106, 107, perennial -47, 68, 111, 170 147, 148, 149, 150, 169 pericarp - 25 nitrate • 70, 71, 73, 74 Pcrlette ■ 118, 145 nitrate reductase • 71 Perlite • 33 nitrogen • 27, 52, 56, 69, 70, 71, 72, 73, 74, 76, permanent support ■ 56, 61 77, 79, 80, 87, 90, 100, 118, 119, 164, 172 pests 24, 30, 31, 34, 35, 47, 57, 66, 71, 104, litrogenous materials • 21 105, 106, 107, 108, 110, 114, 147, 163, 164 loble rot • 100 petals • 23, 163, 164 lodosites • 106 Petiole sinus 139, 140, 141, 142, 143, 144, lodules • 70 145, 146, 149, 150 ion-climacteric 114 petioles -80,89, 90,91,92, 111 non-irrigated • 55. 120 Petit Syrah • 143 notch grafting • 36 pH 35, 42, 43, 65, 68, 74, 76, 79, 80, 83, 85, nourishment. • 55 86,87, 88, 114, 115, 123, 162, 168 nursery soil -30 phenology • 21 nutrient • 67, 70, 80, 87, 96, 112, 164 phloem • See morphology nutrient status • 68 phomopsis • 143, 144 nutrient use efficiency • 68, 73 phosphorus ■ 1, 69, 70, 75, 87, 90, 119 nutritional disorders 112 photomorphogenesis • 63, 65 photoperiodic control • 96 photosynthate • 21. 23 o photosynthesis • 18, 19, 25, 34, 63. 65, 66, 79, 167 phylloxera -4, 71, 106, 147 oblate • 139, 140, 145 Physical treatments • 122 obovoid •144 physiology • 25, 42, 65, 69, 114 odorous compounds 114 phytochrome - 65 off-flavor • 99 Phytophthora • 99 olive oil 130 phytosanitary -101 omega cut • 33 phytotoxicity ■ 98 omnivorous ■ 104 pigmented varieties • 114, 115, 119 orchard ■ 47 pigments • 114, 115 organic acids ■ 21, 25, 26, 76 Pinot Noir • 143 organic matter 70, 76, 78, 80, 93, 164, 166 pistil • See Blooming organisms • 36, 42, 45, 70, 115, 126, 163 plantation - 67 Orthodox Church. • 1 planting materials • 1,9, 10, 49, 50, 51 oval • 17, 139, 140, 141, 142. 144 plastic sheet - 33, 131, 132 over cropping • 60, 84 poisoning • 109 The Grapevine pollen grain • 13, 45, 171 rainfall • 9, 52, 55, 100, 120, 128, 162 pollen lube • 23, 82 raisin • 1, 4, 5, 8, 9, 50, 97, 102, 113, 127, 128, pollination • 23, 57, 83, 1 18 129, 131, 132, 133, 134, 135, 138, 147 pollution • 42, 70 raisin grapes ■ 4, 8, 113, 127 polypropylene twine • 28 rate • 78, 98, 99, 105, 162, 166 polysaccharides • 26 ray cells • 21 pomace ■ 74 re-grecning • 86 Post-drying • 132 replacement canes • 120 Post-harvest handling • 126 research ■ 1,57,62,67, 108, 114 potash ■ 76, 77 resistant • 82, 98, 106, 107, 139, 142, 143, 148, potassium ; 26, 65, 69, 70, 75, 76. 77, 79, 90. 92 149, 150 poultry manure ■ 74 rest -4,21,48, 61, 171 powdery mildew 141 retardant -65, 122 powdery mildew -31, 96, 97, 98, 99, 139, 142, Ribier • 145 143 richness - 7 precipitation -49, 100 Ridomil 99 predatory mites • 98, 99, 104 Ridomil Gold • 31 Pre-drying • 129 Riesling • See VARIETIES premature drop - 99 riparia • 3, 150 premium fruits • 125 ripening ■ 9. 26, 55, 64, 65, 68, 72, 76, 96, 99, preservation ■ 108 100, 103, 105, 110, 114, 117, 118, 119, 120, preventive spraying • 99 122, 123, 163, 164, 165, 171 production - 2, 4, 5, 6, 7, 8, 9, 12, 14, 27, 30, 33, ripening berries - 55 35. 41, 48, 57, 59, 60. 62, 67, 70, 95. 96. Roadway packing • 125 101, 106, 111, 113, 118, 120, 128, 136, 137, rodents • 30 138, 162,166 Root exudates - 20 productivity • 48. 55, 57, 62, 64, 66, 67, 68, 74, Root knot nematodes • 32 83, 95, 119 root system • 34, 55, 56, 58 proliferation • 6. 97 rooted cuttings • 30, 31, 32, 51, 52, 102. 138 propagation • 12, 30,41, 101, 102, 103, 104, root-feeding • 106 164 roolings ■ 31 protection • 29, 34, 64, 66, 97, 100, 109, 119 root-knot nematode • 107 proteins • 26, 70, 76, 85, 165 rool-rot • 99 pruning • 20, 21. 27, 50, 54. 57, 58, 59, 60, 61, roots ■ 10, 19, 20, 27, 31, 32, 41, 48, 52, 53, 70, 62, 63, 64. 66, 74, 81, 88, 95, 96. 111, 120, 73, 85, 106, 107, 108. 149, 167, 169 123,153 rootstock ■ 4, 30, 32, 33, 35, 38, 46. 65, 111, pruning shears 117 138, 147, 148, 149, 169 pubescence -4, 105, 140, 171 rootstock varieties ■ 33 pubescent 13, 139, 148 Rootstocks • 33 pulp • 115, 133, See lruit rotary-hoe • 30 punetiform • 76 rotundifolia • 3 pyriform • 3 Row packing ■ 125 row spacing 118 Rubired • 92 o rudimentary leaves - 13. 95 rupestris • 3 quality 115 quiescence • 21 s R saline soils • 48, 94 sandy loam • 30, 72, 73 Sangiovese 141 Rabbits • 109 Saturation percentage • 88 rachis • See The flower Sauterous • 100 Rack spraying • 132 Sauvignon blanc • 142

[179] Asfaw Zelleke sawdust ■ 30. 32, 33 sporulation 99, 102 scale insects • 104 spraying - 50, 57, 99, 100, 105, 124, 131, 165 scales • 104. 125, 163. 169 spraying equipment 100 scarring 104, 105 Sprig- 116 scion chip • 38 sprinkler - 169, 170 » scion wood • 28, 29, 33, 39, 40, 52 sprinkler irrigation 55 Scion wood • 33 spur pruning • 60 seeded varieties • 23 spur-pruned ■ 59, 81 seedlings • 27 stake -46, 56, 58, 172 seeds -3, 18, 30, 81, 103, 118, 128, 136. 162, stamens • See flower 164, 169, 171 starches, • 76 Semilion • 142 stenospermocarpy. • 23 Sexual propagation • 27 sterilants • 45 Shade packing 125 sterile 13, 148, 149, 150 shading 23, 64, 65, 120 sterilization • 42. 45 shatter" 23, 83, 122, 126, 127 stigma • See flower shield budding • 39 stimulative parthenocarpy 23 shoot • 11, 12, See morphology stipular 147 shoot stunting • 104 storage 10, 19,21, 29, 52, 66, 71, 74, 100, 117, shoot thinning • 120 118, 124, 125, 126, 127. 129. 132. 133 shoot tip 45, 102 Storing • 32 shoot trimming • 64 straggly eluster 121 shoot-tip 43 stripping 66, 109 Shoot-tip culture • 45 strychnine 109, 110 shot berries 81, 103 stump 37 shot-hole 101 style 171 ihouldcred 139, 140, 141, 145, 146 sub soils 48 shrubs • 3 succinic acids 115 sigmoid growth pattern • 25 suckering • 33, 120, 164 single crop • 56 sucking mouth 106 smothering • 54 sugars ■ 20,21, 24. 26, 43, 76, 114, 134, 164, SO, • 117, 118 165 soda dipped 129 Sugars-acid ratio 115 soda oil 129 sulfate of potash • 77 sodic soils • 48, 78, 93 sulfur 69, 70, 97, 98, 100, 105, 117, 126 sodium bicarbonate • 130 sulfur bleached • 129 sodium ions ■ 48 sulfur dioxide • 100, 126, 130 sodium sulphate • 48 Sulfur dusting ■ 97 soft woodcuttings 41 sulfur fumes • 130 soil additive • 85 sulfur house 130 soil amendments • 86 Sulfur-bleached 130 Soil analysis ■ 67, 77. 81, 88 Sun drying 131 ‘oil colloids • 86 sun radiation 131 soil microbes 70 sunshine hours • 96 soil moisture -81, 120 support 12, 56, 57, 58, 60, 67, 169 soil profile • 55, 75, 77 sweet wine 139 solar radiation 50, 64 symptoms • 67, 70, 75, 76, 77, 78, 79, 80, 81, solution • 20, 29, 32, 33, 75, 81, 82, 86, 98, 117, 83,85, 90, 94, 105, 106, 112 130, 131, 132, 168 syndromes • 103 solution extracts - 88 synerged cell • 23 sparkling wines • 139 Syrah 111 species - 3, 7, 12, 13, 19, 36, 46, 68, 102, 104, syrup • 129, 136 * 106, 108, 110, 166, 172 spider mites • 98, 104 / spoilage ■ 115, 126, 129, 136 spores -97, 98, 101, 127

[180] The Grapevine

T u

T budding • 33, See Ugni blanc • 120. 139 T cut • 39, 40 unilateral • 58, 61 tabic grapes • 4 ,6 1 , 118, 119, 120. 124. 127, uracil • 23 136 urea -31. 55, 56, 7 3 ,7 4 ,8 7 , 119 table wine • 113, 141 tannins 114 tartaric acid 1, 26. 123, 167 V taste panels • 65 'I eflon -training • 62 variegated cane 111 temperate • 4, 6, 13, 21, 47, 95, 96 variegation 111 temperate /ones • 6, 48, 57, 96 varieties ■ 8, 9, 115, 116, 120, 121, 123, 124, temperature ■ 6, 19 127, 129. 136, 138, 147, 149, 162, 170 temporary support • 56 vascular rays ■ 21 tendril • 12 vascular tissues • 34 tendrils ■ 3, 1 I, 12, 21, 99, 103, 140 vegetation -70, 103, 104 termites • 56, 104, 106 vegetative cycle ■ 48 texture - 5, 24, 48. 74, 88, 118, 129, 132. 170 vegetative growth • 22, 71, 96, 98 thallophyte 113 vegetative phase ■ 25 thermal death - 29 veins • 71, 79, 83, 86, 93, 103, 105 tliiophanate 101 verasion ■ 18, 24. 26, 64, 69, 80. 100. 101.114, Thompson Seedless • 92, 146 122 Thrips ■ 104 Vermiculite • 33 tipping ■ 121, 122 vertical cordon - 58. 59 tissue analysis - 56, 67, 71, 72, 79, 81, 85, 89, vetches - 70 119 vine vigor • 70, 71 tissue injury • 29 vineyard • 1. 30, 33, 34, 47, 48, 49, 50, 51, 52, titratable acidity • 25. 65, 1 15, 123. 133 54. 59. 62. 72, 74, 76. 77, 80. 81. 96, 101. top grafting • 35 103, 105, 109, 110, 111, 113, 117, 119. 141 top working - 35, 36 vineyard industry’ • 67 topography • 48, 50 vineyard management 66 topping • 122 vineyards • 1, 4, 9, 28, 31, 47, 49, 50, 51, 55, 56, total soluble solids • 5, 9, 115, 123 64, 67, 68. 69, 70, 72, 75, 76, 77, 78, 79, 81, toxic salts • 49 84, 96, 97, 98, 101, 104. 107. 108, 109, 110, toxicity symptoms ■ 89 116, 121, 125, 133, 152, 153 training • 14, 23, 50, 54, 56, 57, 58, 60, 61, 62, vinifera • 3. 4, 6. 7. 12. 13, 48, 136, 149, 150 63,64, 100. 141, 144, 145, 163, 172 viruliferous 107 training system • 56, 64 virus 45,46, 81, 102, 103, 104, 107, 111, 164, transpiration • 20, 63 166, 169 trapping - 109, 110 virus-free • 104 trellis -50, 57, 58, 59, 60, 61, 62. 64, 102, 1 16, visual symptoms • 70 119, 131, 172 Vitaceae - See family trellis post • 50 vitamins 1, 26, 133 'Irellising • 57, 66, 119 viticulture ■ 2, 6, 9,41, 48, 50, 62, 67, 69, 96, trench • 30, 41 101, 102, 114, 117, 118 I riadimefon 98 Vitis vinifera - 3 trim • 125 volatilization • 74 tropics • 6, 52, 95, 96, 97. 104 trunk ■ 11 tuberosites. • 106 twig borer • 104 w

water ■ 19, 20, 49 water bath • 42

[181] Asfaw Zelleke water holding capacity 48, 64 wine grapes 4, 113, 114, 115, 116 water sprouts • 59 wine varieties 113 water stress ■ 26, 55, 114 wineries I, 2, 4, 115 water supply • 53, 114 wines • ii. 2, 7. 8, 48, 63, 65, 100, 115. 117, 118, watery berries • 55 136, 140, 143, 169. 170, 172 weather • 7, 23, 31, 48, 51, 77. 96, 97, 98. 101, winged 139, 140, 141, 142, 143. 145. 147 102, 105, 114, 124, 129, 130, 131. 132, 133, witches broom 107. 111 163 weathering • 76, 82 wedge • 37, 38 Y weed • 54, 105, 164, 167 weed pressure 56 yeast - 113, 114,133, 165 weeds -3 1 ,3 4 ,4 9 , 54, 170 yellow mosaic • 103 Well-drained soil • 30 yield 51. 59, 63. 64, 65, 69, 76. 99, 103, 118, weltable sulfur ■ 97, 98, 99 119, 155, 159 wetting agent • 98 Whip gralling • 35 White Wine • 138 wild animals • 30 z wild yeast 113 wind - 30, 56, 63, 118, 131, 165 Zcwai 1. 9, 58 windbreak • 34, 56 /inc 22, 69, 70, 74, 80, 81, 82, 83. 87. 90, 96 wine • 1, 4, 5, 7, 8, 26, 51, 60, 61, 64, 65, 97, /ineb. • 99 113. 114. 115, 116, 117, 119, 128, 138, 140. zygote 23, 165 143, 145, 147, 149, 162, 163, 167, 169, 171

[182] indorsement

...... I have the utmost pleasure of having reminiscences of my wonderful and pleasant indulgence in furthering the cause of horticulture development in Ethiopia through my capacity building initiatives of my students at the then Alemaya University, Alemaya from 1999-2003. During this time, I had the overwhelming influence of Dr. Asfaw Zelleke and his zeal and endeavors to stabilize viticulture industry in Ethiopia which also included approaches to improve productivity and profitability of grape growing in the country. At that time, it had also been realized that there was no authoritative treatise on viticulture articulating Ethiopian agro-ecology that prompted Dr. Asfaw Zelleke through his acquired fellowship and training under the world famous viticulturist Prof Olmo, University of California, USA to organize the present authoritative compilation so crucial to the students, researchers and extension workers in the country. I, for a good number of years, had the opportunity to go through different chapters of this book critically and offered some suggestions. Different parts of Ethiopia, 1 am confident, through my own journey during my stay in the country offers unlimited opportunities for exploiting commercial viticulture for table, vine and raisin grapes production by pursuing scientific viticulture for which the present dedication by Dr. Asfaw Zelleke undoubtedly will be a priceless gem . With integration and optimization of rootstock, 4Dogridge’, suitable varieties , improved crop husbandry including canopy and pests and diseases management technologies in commercial viticulture , 1 am sure Ethiopia would be able to harness the true potential and dreams of Dr. Asfaw Zellekc’s contributions to stabilize commercial viticulture in Ethiopia. I wholeheartedly congratulate him for this great contribution and assure him of my fullest support in all his future endeavors.

Dr H.Ravishankar, Director Central Institute for Subtropical H orticulture (ICAR) Rehmankhera, P.O.Kakori, Lucknow-226 1 0 1 U ttar Pradesh, INDIA (E m a il: [email protected]}

[183] a - ;v.:

Ethiopia has great agricultural potential because of its vast areas of fertile land, diverse climate, generally adequate rainfall and large labor pool. The countiy can achieve swift and sustainable long-term economic development through agriculture sector especially horticulture subsector.

Horticulture is one of the most important parts of agriculture which plays a pivotal role in the bod and livelihood security in Ethiopia. The commercialization of agriculture and promotion of agri-business is correlated to the progress in horticulture subsector. Thus horticulture plays a vital role in the up-liflment of community mid national development. Agro-climatic conditions in Ethiopia are most suitable for successful production of wide variety of horticultural crops. Given the diverse range of altitudes in combination with irrigation potential in different parts of the country, it is possible lo produce virtually all tropical, sub-tropical and temperate horticultural crops. Due lo the presence of favorable government policies for agriculture, particularly horticulture subsector, production of a variety of horticultural crops by the state owned farms and private farms owned by investors and progressive farmers is expanding from time to time.

Grapevine is an important fruit crop grown in temperate, sub-tropical and tropical climatic conditions and under varied agro-ecological settings. Now grape cultivation has become one of lhe most remunerative farming enterprises of the present time in the world. Globalization has opened a new era for competitiveness in the production and marketing of Horticultural crops. In Ethiopia, the huge advantage of grapevine cultivation in terms of its significant economic importance as a potential source of national revenue is unequivocal. Grapevine is unique in nature. To achieve successful and sustained production of good quality crop, application of appropriate knowledge and management practices of the grapevine is required. To this end therefore, standard grapevine production and management guide is vitally important.

Dr. Asfaw Zelleke, who has a wealth of teaching, research and advisory experiences 011 grapes, has written a book which provides comprehensive information 011 global and local experiences of grape production (Viticulture). The focus in this book is on practical advice, with emphasis on the Ethiopian experience, and includes the following topics: structure and growth processes of the grapevines, propagation, vineyard establishment and management practices including training, pruning, diseases and insect pest management, plant nutrition, and postliarvest management of the grape. The book also describes the major grape varieties grown in Ethiopia and comprises of a very clear glossary 011 viticulture. It is oriented for a large array of readers in agriculture and horticulUire and gives a comprehensive picture on the production and processing scenarios of viticulture in the country. 1 feel that students, teachers, researchers, development and extension workers, fanners and interested persons in the field of Horticulture/Viticulture will be immensely benefited. The author deserves special credit for publishing this useful book especially in view of the fact that the Government of Ethiopia is currently encouraging the horticulture subsector. 1 congratulate the author for the excellent efforts in bringing out this interesting and useful book which is very timely and vital.

Derbew Belew (Ph.D) H orticulturist, Jim m a University

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