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Identifying Elite Rhizobia for Commercial Soybean

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Identifying Elite Rhizobia for Commercial Soybean IDENTIFYING ELITE RHIZOBIA FOR COMMERCIAL SOYBEAN (GLYCINE MAX) INOCULANTS MAUREEN N. WASWA BSc Horticulture (JKUAT) THESIS SUBMITTED IN PARTIAL FULFILMENT FOR THE AWARD OF DEGREE OF MASTER OF SCIENCE IN SOIL SCIENCE DEPARTMENT OF LAND RESOURCE MANAGEMENT AND AGRICULTURAL TECHNOLOGY, UNIVERSITY OF NAIROBI 2013 1 DECLARATION This thesis is my original work and has not been submitted for a degree in any other University Signature………………….. Date…………………… Maureen Nekoye Waswa This thesis has been submitted for examination with our approval as supervisors 1. Signature……………… Date…………………… Prof. Nancy Karanja (UoN) 2. Signature……………… Date…………………… Dr. Paul Woomer (CIAT-TSBF) 3. Signature……………… Date…………………… Dr. Frederick Baijukya (CIAT-TSBF) i DEDICATION To: my father, Chrispus W. Wanjala; my mother, Norah N. Wanjala; and my brothers and sisters. My parents’ vision for a better tomorrow is unrivalled by the best educators in my life. Above all I extend my sincere gratitude to the Almighty God for making this journey possible. ii ACKNOWLEDGEMENT I take this opportunity to express my gratitude to my supervisors Prof. K.N Karanja (University of Nairobi), Dr. Paul L. Woomer (CIAT-TSBF) and Dr. Frederick Baijukya (CIAT-TSBF) for their constant expert guidance, advice and support through all the stages of the research work. I also wish to thank all technicians in the department of LARMAT particularly Stanley Kisamuli for the encouragement and support provided during my research. My gratitude also goes to the Bill and Melinda Gates Foundation for funding my course and research work through N2Africa project. Appreciation also goes to my husband, Andrew S. Mabonga for his support during long period of my study. Special thanks also go to my daughter Faith N. Mabonga; she made my work easier and tolerated my absence from home at a time that she needed me most. iii TABLE OF CONTENTS DECLARATION ...................................................................................................................... i DEDICATION ......................................................................................................................... ii ACKNOWLEDGEMENT ...................................................................................................... iii TABLE OF CONTENTS ........................................................................................................ iv LIST OF TABLES .................................................................................................................viii LIST OF FIGURES ................................................................................................................ ix PLATE .................................................................................................................................... ix ABBREVIATIONS AND ACRONYMS ................................................................................ x ABSTRACT............................................................................................................................xii CHAPTER ONE ...................................................................................................................... 1 INTRODUCTION ................................................................................................................... 1 1.1 Background ........................................................................................................................ 1 1.2 Problem statement and justification ................................................................................... 3 1.3 Objectives .......................................................................................................................... 4 1.3.1 Broad Objective .............................................................................................................. 4 1.3.2 Specific Objectives ......................................................................................................... 5 1.3.3 Hypothesis ...................................................................................................................... 5 CHAPTER TWO ..................................................................................................................... 6 LITERATURE REVIEW ........................................................................................................ 6 2.1 Characteristics of rhizobia ................................................................................................. 6 2.2 Rhizobial Taxonomy .......................................................................................................... 7 2.3 Rhizobial Ecology and Diversity ....................................................................................... 8 2.4 Determinants of Host Specificity in Rhizobia ................................................................. 11 2.5 Mechanisms of Biological Nitrogen Fixation .................................................................. 12 iv 2.6 Significance of Biological Nitrogen Fixation .................................................................. 14 2.7 Rhizobial Bio-prospecting Studies .................................................................................. 15 2.8 Factors affecting Nitrogen fixation .................................................................................. 17 2.9 Nitrogen Fixation in Soybean .......................................................................................... 20 CHAPTER THREE ............................................................................................................... 24 MATERIALS AND METHODS ........................................................................................... 24 3.1 Site description ................................................................................................................ 24 3.2 Authentication and screening of indigenous rhizobia isolates in the greenhouse collected from soils under different land uses in Kenya. ....................................................... 25 3.2.1 Authentication of indigenous rhizobia isolates in the greenhouse collected from soils under different land uses in Kenya. ............................................................................... 25 3.2.1.1 Design used for the authentication experiment in greenhouse ................................... 25 3.2.1.2 Preparation of potting media ...................................................................................... 26 3.2.1.3 Pre-germination of seeds............................................................................................ 27 3.2.1.4 Planting and inoculation of bacterial isolates ............................................................ 27 3.2.1.5 Nutrient solution ........................................................................................................ 28 3.2.1.6 Harvesting authentication experiment ....................................................................... 28 3.3. Screening of indigenous rhizobia isolates in the greenhouse on performance of specific (Safari) and promiscuous (SB19) soybean grown in non sterile soil from Western Kenya ..................................................................................................................................... 29 3.3.1 Experimental design of screening test in greenhouse using non sterile soil ................. 30 3.3.2 Rhizobia used for potted non-sterile soil experiment in greenhouse ............................ 30 3.3.3 Performance of 24 indigenous rhizobia isolates inoculated on soybean grown in Butula soil in the greenhouse ................................................................................................. 32 3.4 Field trials to assess performance of promising indigenous rhizobia using promiscuous (SB19) and specific (SB97) soybean ................................................................ 33 3.4.1 Experimental design used in the field assessment of the indigenous rhizobia isolates . 33 v 3.5 Procedures for chemical characterization of soil and vermiculite ................................... 35 3.6 Statistical analysis ............................................................................................................ 38 CHAPTER FOUR .................................................................................................................. 39 RESULTS .............................................................................................................................. 39 4.1 Characteristics of media used in the greenhouse and field level ..................................... 39 4.2 Authentication and screening indigenous rhizobia isolates collected from soils under different land uses in Kenya. ................................................................................................. 40 4.2.1 Authentication of indigenous rhizobia isolates in the greenhouse using sterile media . 40 4.2.1.1 Nodule number and internal nodule color.................................................................. 42 4.2.2 Screening of indigenous rhizobia isolates in the greenhouse on performance of soybean varieties grown in soil from Butula-Western Kenya ............................................... 44 4.2.2.1 Nodulation of promiscuous (SB19) and specific (Safari) soybean ............................ 44 4.2.2.2 Plant biomass for SB19 and Safari inoculated with promising rhizobia isolates grown in soil collected from Butula at greenhouse level ......................................................
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