\ . 1 ..r " 'i! .s» © Olabisi Onabanjo University Press, Ago-Iwoye, 2004. MAN AND PLANT MICROBES STRUGGLE: A WINNER? All rights reserved. No part of it may be reprinted, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, electrostatic, magnetic tape, photocopying, recording or otherwise, without the prior written permission of the copyright owner. First Published, March 2004. BY ISBN 978-36556-4-7 PROF.AFOLABIADEBANJO .. Published by Olabisi Onabanjo University Press P.M. B. 2002, Ago-Iwoye, Ogun State. Nigeria. 29TH INAUGURAL LECTURE OLABISI ONABANJO UNIVERSIlY AGO-IWOYE. Tuesday, 16th March, 2004 Table of Contents Page Content List 2 Table List 3 Preamble 4 1.0 The Historical Background 5 1.1 Microbes and Plant Diseases 7 ~'TOTHE TEACHERS WHO TAUGHT ME 2.0 Fungi as Pathogens 8 AND 3.0 BacteriaAs Pathogens 9 THE STUDENTS WHO r~SPlRE ME" 4.0 Post-Harvest Losses 10 4.1 Causes of Losses 11 4.2 Pathological Attack 11 4.3 Economic Significance of Diseases Caused By Microbes 12 5.0 Weapons of Microbial Attack 15 6.0 Weapons of Plant Defence 19 7.0 Weapons of Man Against Microbes 20 Acknowledgments 28 References 34-35 2 List of Tables MAN AND PLANT MICROBES STRUGGLE A WINNER? Tables Content Page 1 Characteristics of Important Plant The Vice-Chancellor, Principal Officers of the University, Pathogenic Bacteria 9 Provosts of Colleges and Deans of Faculties, 2 Mycotoxins In Staple Grains And Seeds 13 Colleagues, Friends from Sister Universities and Research Institutes, 3 Examples of Severe Losses Caused Royal Highnesses, Chiefs, Lords: Spiritual and Temporal, Distinguished Ladies and Gentlemen, by Fungi and Bacteria 15 GreatOOUITES! 4 Estimated 1982 World Crop Production I feel highly honoured to be invited, to deliver the 29th and Preharvest Losses (in Millions of Tons) Inaugural Lecture of this great University today. It is the fifth of its series from the Faculty of Science and the third from the Department and Percent of World Production Lost to of Biological Sciences of this noble institution. Diseases, Insects and Weeds 16 PREAMBLE 5 Estimated 1982 World Crop Production Iwas appointed by this University as a Lecturer I about 18 and Preharvest Losses (in Millions of Ton) years ago necessitating the transfer of my service, from the National and Percent Lost to Other Pests (Insects, / Horticultural Research Institute, (NIHaRT), Ibadan, Nigeria. I stand before you today as a Professor, a post to which I was promoted Weeds) in Developed and Developing Countries. 18 in the year 2000 to share with you, part of my research experience to date. My interest in the study of plants was stimulated while studying "Nature Study" as a subject in the Secondary Modern School in 1963. This interest was further strengthened when I offered Botany, Zoology and Chemistry as major subjects during my Higher School Certificate studies in 1970. Consequently, I was offered an admission to study Special Honours Botany at the University of Lagos for my undergraduate programme. Broad topics covered for the then almighty June final examinations which intensified my interest further still, included Economic Botany," Plant Physiology, Mycology, Bacteriology, 3 4 Microbial Physiology and Loss of crops and farm produce to references in the history of the ancient Hebrews to blights and microorganisms among others. mildews of the cereal and vine crops upon which the people depended Due to my very brilliant performance at the undergraduate heavily. level, I was offered direct admission for the M.Phi!. programme at Greek Philosophers, such as Theophrastus (370-286 B.C.) noted the the then University ofIfe, now Obafemi Awolowo University, (0. A. occurrence of crop maladies and speculated as to their cause and U). My study then focussed on the survival of the water-yam cure. Down through the Middle Ages, we find that scholars were anthracnose pathogen, Colletotrichum gloeosporioides, resulting impressed by the appearance of plant diseases but were quite in publications by Adebanjo, 1980, Adebanjo and Onesirosan, 1986. confused as to the factors which brought them about. Scientific This marked the beginning of my interest in disease causation to experiments were not common, but the occasional keen observer of plants and the difficulties encountered in the management and/or nature was hampered by the current custom of explaining natural eradication ofthe causal agents. phenomena by the process of deductive reasoning. Incorrect interpretations, based on unsound analysis of facts and greatly The topic of my lecture - MAN AND PLANT MICROBES int1uenced by superstition and religious dogmas, were passed from STRUGGLE: A WINNER? - is suggestive of a battle between one generation to another until they became accepted as hard and fast man and plant microbes, which seems to have been consistently won laws of nature. by the latter. Man is the highest of God 's creation and also the Homo At the close of the 18th century, there was no evidence that sapiens, wise man while microbes are organisms, that can be seen modem concepts of the nature of disease inception in plants and the with the aided eyes, but are found in large numbers everywhere relation of environment to disease development had been adopted by including places like inside water, the moon, inside rocks, on ice that those concerned with plant science and plant culture. are not even habitable by man! In other words, both man, plants and The invention of the microscope however, in the 17th century gave microbes have existed side by side for several years, with man not vision to the hitherto unknown world of microbes. Leeuwenhoek being able to see the microbes until in the nineteeth century, but all discovered bacteria in 1675. the while seeing and experiencing the effects of their act' zities, An Italian botanist Micheli in 1729 made an extensive study of especially the adverse effects which helped to draw attention to them fungi and their reproductive structures. He discovered the role of (Kolawole,1997). spores and experimentally proved that the fungi originated from their spores. This was the first experimental proof that fungi are 1.0 THE HISTORICAL BACKGROUND autonomous organisms which produce seed-like bodies and not The earliest records of man reveal that as he began to depend capricious creatures of the spontaneous generation. upon cultivated food ,feed and fibre plants for his livelihood, the On the other hand using his series of simple microscopes Van problems of crop losses, food shortages, and famine continually Leeuwenhoek also reported the presence of minute living creatures in arose to plague him. The Old Testament (Gen. 41 :23; I Kings 8:37; water from different sources and in decaying animal and vegetable Amos 4:9; II Chron. 6:28; Deut. 28:22; Hag. 2:16-17) made matter which had been left to stand for a week or two at room 5 6 temperature. Augustino Bassi in 1836 showed that the calcino My work over the past 27 years has been mainly in the field of disease of silkworms was caused by a fungus which invaded their myco logy and bacteriology and therefore, for the rest of this lecture, I tissues and could be transmitted by the inoculation of material from shall be reporting observations made mainly on fungi and bacteria such tissues into those of healthy ones. These observations, together especially their involvement in plant diseases and the effort made by with the availability of improved microscopes, initiated the man to control them. systematic description of micro-organisms. In 1840, Henle had pointed out that a microbe causing a 2.0 FUNGIAS PATHOGENS disease should be present in every case and should be able to produce Fungi pathogenic to plants are many and diverse. They 'exhibit a similar disease in animal into which it was later inoculated. These greater diversity in form, function and life history than other principles for establishing the causal organism of a disease were pathogens. They have also been known as plant pathogens for a later expanded in 1870 by Robert Koch to become what are longer time than other organisms. All the major groups of fungi have collectively called "Koch's pestulates" today. Koch and his students important plant pathogens. Thus, Olpidium, Plasmodiophora, subsequently identified the causal organisms of tuberculosis, Phytophthora, Pythium, Aphanomyces and the downy mildew fungi, cholera, typhoid and many other major diseases of man and animals. (Peronospora, and Plasmopara) are the best known pathogens.from With the establishment of the link between microbes and phycomycetes. In Ascomycotes, the powdery mildews, Penicillium, many diseases of plants, the battle line between man and the Claviceps, and Monilia cause serious plant diseases. Basidiomycetes microbes was at last clearly drawn. The nature of this battle and its include the elite among pathogens-the rusts, and those that transform present status, constitute the theme of my lecture today. cereal grains into nothing less than a mass of black powder, the smuts. In addition, the wood-rotting fungi Armillaria, Fomes and the like, 1.1 MICROBES AND PLANT DISEASES have led to total collapse of wooden buildings. The organisms collectively called mircobes cut across The Deuteromycetes which include the Fusarium, the Verticillium, disciplines. These include the algae, protozoa, fungi, viruses, the Rhizoctonia, the Piricularia and others also cause severe ravages bacteria, nematodes, richettsia-Iike and mycoplasm .-like on plants or their produce. orgamsms. Fungi have made history in all parts of the world by causing They are found, like I said earlier in widely diverse habitats, ranging catastrophic diseases. The late blight disease of potato in Ireland, the from hot springs to human body, in soil, in air, in foods, in petroleum powdery mildew of grapes in France, the chestnut disease in the USA oil, plants, and plant produce as well as at the depths of the ocean.