FITNESS, VIRULENCE AND GENETIC VARIABILITY IN PYRENOPHORA TRITICI-REPENTIS ISOLATES CAUSING TAN SPOT OF WHEAT IN OKLAHOMA By KAZI ABDUL KADER Bachelor of Science in Agriculture Bangladesh Agricultural University Mymensingh, Bangladesh 1990 Master of Science in Plant Pathology Institute of Postgraduate Studies in Agriculture Gazipur, Bangladesh 1995 Submitted to the Faculty of the Graduate College of the Oklahoma State University in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY May, 2010 FITNESS, VIRULENCE AND GENETIC VARIABILITY IN PYRENOPHORA TRITICI-REPENTIS ISOLATES CAUSING TAN SPOT OF WHEAT IN OKLAHOMA Dissertation Approved: Dr. Robert M. Hunger Dissertation Adviser Dr. Mark E. Payton Dr. Hassan A. Melouk Dr. Jeff T. Edwards Dr. Stephen M. Marek Dr. A. Gordon Emslie Dean of the Graduate College ii ACKNOWLEDGMENTS I express my sincere gratitude to my mentor Dr. Robert M. Hunger, for accepting me as a graduate student, for his guidance, suggestions and insights, and instructions throughout my study and research. His tremendous faith in my abilities and unwavering support to me made this research possible. I enjoyed every freedom to think and work independently. His door was always open for me to discuss any research idea that came to my mind or even my personal problems. Whenever I had difficulties, I had him by my side. Many days he took me to visit wheat fields in Oklahoma and taught me how to apply plant pathology in a practical situation. He took me to several professional meetings, workshops and seminars so that I could participate, enjoy and learn. I will never forget those days. His all-time inspiration will influence me forever. Sincere appreciation is due to my committee members, Dr. Mark E. Payton, Dr. Hassan A. Melouk, Dr. Jeff T. Edwards and Dr. Stephen M. Marek, for their help, advice, instruction, constructive criticism, and time spent on this study. Deep appreciation is due to field technicians, personnel in the department, and all of my friends for their care, humor and help during the period of study. I also extend my special thanks to the Oklahoma Wheat Research Foundation and the Oklahoma Agricultural Experiment Station for providing me financial support for this research. iii TABLE OF CONTENTS Chapter Page I. INTRODUCTION ......................................................................................................1 II. REVIEW OF LITERATURE....................................................................................6 History of tan spot in wheat .....................................................................................6 Disease symptoms and yield loss ............................................................................7 Pathogen biology .....................................................................................................8 Host range ................................................................................................................9 Infection and host-pathogen interaction...................................................................9 Host-specific toxins ...............................................................................................10 Genetics of pathogen and disease resistance .........................................................12 Races of Pyrenophora tritici-repentis ...................................................................13 Genetic diversity of Pyrenophora tritici-repentis ..................................................14 Disease cycle and epidemiology ............................................................................16 Management of tan spot in wheat ..........................................................................20 III. GROWTH, SPORULATION AND PSEUDOTHECIA PRODUCTION OF PYRENOPHORA TRITICI-REPENTIS ISOLATES COLLECTED IN THREE DECADES FROM WINTER WHEAT IN OKLAHOMA ....................23 Abstract ..................................................................................................................23 Introduction ............................................................................................................24 Materials and Methods ...........................................................................................26 Results ....................................................................................................................31 Discussion ..............................................................................................................32 Acknowledgments..................................................................................................35 Literature cited .......................................................................................................36 iv Chapter Page IV. VIRULENCE OF PYRENOPHORA TRITICI-REPENTIS ISOLATES, YIELD LOSS, AND EVALUATION OF WHEAT RESISTANCE TO TAN SPOT IN OKLAHOMA ........................................................................................................44 Abstract ..................................................................................................................44 Introduction ............................................................................................................45 Materials and Methods ...........................................................................................48 Results ....................................................................................................................52 Discussion ..............................................................................................................53 Acknowledgements ................................................................................................56 Literature cited .......................................................................................................57 V. RACE STRUCTURE, SYMPTOMS, AND GENETIC RELATIONSHIP IN PYRENOPHORA TRITICI-REPENTIS ISOLATES COLLECTED OVER THREE DECADES FROM WINTER WHEAT IN OKLAHOMA .....................64 Abstract ..................................................................................................................64 Introduction ............................................................................................................65 Materials and Methods ...........................................................................................68 Results ....................................................................................................................73 Discussion ..............................................................................................................75 Acknowledgements ................................................................................................80 Literature cited .......................................................................................................80 REFERENCES ............................................................................................................90 APPENDICES ...........................................................................................................103 APPENDIX 1. Pyrenophora tritici-repentis isolates collected from winter wheat field in Oklahoma used in this study .....................103 APPENDIX 2. Races of the fungus Pyrenophora tritici-repentis , the causal organism of tan spot in wheat ....................................104 v LIST OF TABLES Table Page I. Taxonomy of Pyrenophora tritici-repentis ...................................................22 II. Isolates of Pyrenophora tritici-repentis collected from winter wheat field in Oklahoma used in this study ......................................40 III. Analysis of variance for radial growth of seventeen isolates of Pyrenophora tritici-repentis collected from winter wheat in Oklahoma on three media ...................................................41 IV. Mean radial growth of Pyrenophora tritici-repentis isolates on commercial potato dextrose agar (CPDA), PDA made from potatoes (RPDA) and clarified V8 (CV8) juice agar ...........................41 V. Analysis of variance for conidia production of sixteen isolates of Pyrenophora tritici-repentis on leaves of wheat cultivars Deliver, TAM 105 and Red Chief .......................................42 VI. Sporulation (mean ± standard error) of sixteen isolates of Pyrenophora tritici-repentis on clarified V8 (CV8) juice agar and on leaves of wheat cultivars Deliver, TAM 105 and Red Chief. ..................42 VII. Pearson correlation coefficients (r) between the conidiation of sixteen isolates of Pyrenophora tritici-repentis on clarified V8 (CV8) juice agar and on leaves of three wheat cultivars ..............................43 VIII. Total number of pseudothecia and percent mature pseudothecia produced by the isolates of Pyrenophora tritici-repentis collected from winter wheat in Oklahoma ...................................................................43 IX. Analysis of variance for percent leaf area infection of sixteen isolates of Pyrenophora tritici-repentis on three wheat cultivars Deliver, TAM 105 and Red Chief under greenhouse study ..........................60 vi Table Page X. Virulence of sixteen isolates of Pyrenophora tritici-repentis on three wheat cultivars Deliver, TAM 105 and Red Chief under greenhouse inoculation .......................................................................60 XI. Analysis of variance for percent leaf area infection (LAI), yield and thousand kernel weight (TKW) for three isolates of Pyrenophora