SCREENING SELECTED COMMON BEAN GENOTYPES for RESISTANCE to Xanthomonas Axonopodis Pv
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SCREENING SELECTED COMMON BEAN GENOTYPES FOR RESISTANCE TO Xanthomonas axonopodis pv. phaseoli CONSTRAINING BEAN PRODUCTION IN KAKAMEGA COUNTY, KENYA CHEPKEMBOI ANGELINE (B.Sc.) I56/CE/22418/2010 ‘‘A thesis submitted in partial fulfillment of the requirements for the award of the degree of Master of Science (Plant Pathology) in the School of Pure and Applied Sciences of Kenyatta University’’ JULY 2020 ii DECLARATION This thesis is my original work and has not been presented for a degree in any other University. Signature……………………………………….Date…………………………………… Chepkemboi Angeline Department of Plant Sciences Approval by Supervisors This thesis has been submitted for examination with our approval as University supervisors. Signature…………………………………Date……………………………………………. Dr. John Maingi Department of Biochemistry, Microbiology and Biotechnology Kenyatta University Signature……………………………………Date………………………………………… Dr. Shem Nchore Department of Plant Sciences Kenyatta University iii DEDICATION To my loving and caring husband Joseph and children Mercy, Klein, Kelvin and Liance. iv ACKNOWLEDGEMENT My deepest and sincere gratitude goes to my supervisors Dr. John Maingi and Dr. Shem Nchore who were instrumental during the formulation of the research proposal, supervising its implementation and sharing their knowledge and experience. They followed its progress closely providing guidance and encouragement. I am sincerely thankful to the dedicated team of technicians from KARLO; Dr. Reuben M. Otsyula (KALRO-Kakamega) for selflessly giving me professional guidance and counsel throughout this study. I am grateful to KALRO-Kakamega where I did my greenhouse and field research work. Special thanks to Mr. Moses Wambulwa and Mr. Abiud Chesa who guided in the greenhouse and in the field. For all the rest, your prayers played a key role in keeping me focused in the course of my study. May God bless you all. Finally, I appreciate my husband Kurgat and our children Mercy, Klein, Kelvin and Liance who tolerated my absence from home with a lot of understanding. To them I dedicate this work. v TABLE OF CONTENTS TITLE PAGE .......................................................................................................................... i DECLARATION.................................................................................................................... ii DEDICATION....................................................................................................................... iii ACKNOWLEDGEMENT .................................................................................................... iv TABLE OF CONTENTS ...................................................................................................... v LIST OF TABLES .............................................................................................................. viii LIST OF PLATES ................................................................................................................ ix LIST OF FIGURES ............................................................................................................... x ACRONYMS AND ABBREVIATIONS ............................................................................. xi DEFINITION OF TERMS USED ...................................................................................... xii ABSTRACT .......................................................................................................................... xiii CHAPTER ONE .................................................................................................................... 1 INTRODUCTION.................................................................................................................. 1 1.1 Background to the study .................................................................................................... 1 1.2 Statement of the research problem ..................................................................................... 5 1.3 Justification ........................................................................................................................ 6 1.4 Hypotheses ......................................................................................................................... 8 1.5 Objectives .......................................................................................................................... 8 1.5.1 General objective ............................................................................................................ 8 1.5.2 Specific objectives .......................................................................................................... 8 CHAPTER TWO ................................................................................................................... 9 LITERATURE REVIEW ..................................................................................................... 9 2.1 Bean production practices in Western Kenya .................................................................... 9 2.2 Economic importance of Xanthomonas axonopodis pv. phaseoli ................................... 10 2.3 Taxonomy and Morphology of Xanthomonas axonopodis pv. phaseoli ......................... 11 2.4 Biology of Xanthomonas axonopodis pv. phaseoli.......................................................... 12 2.5 Disease symptoms of Xanthomonas axonopodis pv. phaseoli......................................... 12 2.6 Life Cycle of Xanthomonas axonopodis pv. phaseoli ..................................................... 13 2.7 Transmission of Xanthomonas axonopodis pv. phaseoli ................................................. 14 2.8 Infection and host range of Xanthomonas axonopodis pv. phaseoli ................................ 15 vi 2.9 Role of soil amendments on Xanthomonas axonopodis pv. phaseoli .............................. 16 2.10 Effect of maize legume intercropping on Xanthomonas axonopodis pv. phaseoli ........ 17 2.11 Management practices of CBB ...................................................................................... 17 CHAPTER THREE ............................................................................................................. 19 MATERIALS AND METHODS ........................................................................................ 19 3.1 Study area and Study materials ........................................................................................ 19 3.1.1 Study area...................................................................................................................... 19 3.1.2 Study materials.............................................................................................................. 19 3.2 Experimental design and plot size ................................................................................... 20 3.3 Leaf sample collection and bacteria isolations ................................................................ 22 3.4. Pathogen Identification ................................................................................................... 23 3.5. Preparation of growth medium ....................................................................................... 25 3.6 Planting and inoculation .................................................................................................. 25 3.6.1 Greenhouse trials .......................................................................................................... 25 3.6.2 Reaction of nine common bean genotypes to Xap isolates in the field conditions ....... 26 3.7 Effect of soil amendment and method of cropping on CBB disease ............................... 28 3.8 Data collection and disease score .................................................................................... 28 3.9 Data analysis .................................................................................................................... 30 CHAPTER FOUR ................................................................................................................ 31 RESULTS ............................................................................................................................. 31 4.1 Virulence of Xanthomonas axonopodis pv. phaseoli ...................................................... 31 4.1.1 Pathogen characterization ............................................................................................. 32 4.1.2 Pathogenicity test .......................................................................................................... 32 4.2 Screening selected bean genotypes for resistance to common bacterial blight disease in the greenhouse and field conditions .......................................................... 33 4.2.1 Evaluation of selected bean genotypes for resistance to common bacterial blight in the screen house experiment .................................................................................. 33 4.2.2 Field experiment on screening of bean varieties to Common bacterial blight ............. 38 4.3 Effect of soil amendment and method of cropping on incidence and severity of common bacterial blight disease ................................................................................ 42 4.3.1 Effect on disease incidence and severity ...................................................................... 42 vii 4.3.2 Effect of soil amendment on plant growth parameters ................................................. 43 CHAPTER FIVE ................................................................................................................