Host-parasite interaction between the potato tuber rot nematode (Ditylenchus destructor), stem nematode (Ditylenchus dipsaci) and potato Dissertation to obtain the Ph. D. degree in the International Ph. D. Program for Agricultural Sciences in Göttingen (IPAG) at the Faculty of Agricultural Sciences, Georg-August-University Göttingen, Germany Presented by Peter Mwaura Mutua Born in Thika, Kenya Göttingen, December 2014 D7 1. Examiner: Prof. Dr. Stefan Vidal (Supervisor) Department of Crop Sciences, Division of Agricultural Entomology, University of Göttingen, Germany 2. Examiner: Prof. Dr. Johannes Hallmann (Co-supervisor) Fachgebiet Ökologischer pflanzenschutz University of Kassel, Witzenhausen 3. Examiner: Prof. Dr. Andreas von Tiedemann Director of the Department of Crop Sciences, Division of Plant Pathology and Crop Protection, University of Göttingen, Germany Place and date of defense: Göttingen, 2nd February 2015. Table of Contents ACKNOWLEDGMENTS ........................................................................................................................................ I SUMMARY............................................................................................................................................................ III ZUSAMMENFASSUNG ......................................................................................................................................... V CHAPTER 1: .............................................................................................................................................................. 1 GENERAL INTRODUCTION AND LITERATURE REVIEW ............................................................................................. 1 CHAPTER 2: ............................................................................................................................................................ 15 MORPHOMETRICS AND MOLECULAR CHARACTERIZATION OF DITYLENCHUS DESTRUCTOR AND DITYLENCHUS DIPSACI POPULATIONS ............................................................................................................................................ 15 Abstract .............................................................................................................................................................. 16 1.0 Introduction .................................................................................................................................................. 17 2.0. Materials and Methods ................................................................................................................................ 18 3.0. Results ......................................................................................................................................................... 24 4.0. Discussion.................................................................................................................................................... 35 5.0 Conclusion .................................................................................................................................................... 37 References .......................................................................................................................................................... 38 CHAPTER 3: ............................................................................................................................................................ 40 RESISTANCE AND TOLERANCE OF POTATO VARIETIES TO POTATO ROT NEMATODE (DITYLENCHUS DESTRUCTOR) AND STEM NEMATODE (DITYLENCHUS DIPSACI) .................................................... 40 Abstract .............................................................................................................................................................. 41 1.0 Introduction .................................................................................................................................................. 42 2.0. Materials and methods ................................................................................................................................. 44 3.0. Results ......................................................................................................................................................... 49 4.0. Discussion.................................................................................................................................................... 58 5.0. Conclusion ................................................................................................................................................... 63 Acknowledgements ............................................................................................................................................ 63 References .......................................................................................................................................................... 64 CHAPTER 4: ............................................................................................................................................................ 69 EFFECT OF INITIAL POPULATION DENSITIES OF DITYLENCHUS DESTRUCTOR AND DITYLENCHUS DIPSACI ON POTATO TUBER DAMAGE AND NEMATODE REPRODUCTION .................................................................................. 69 Abstract .............................................................................................................................................................. 70 1.0. Introduction ................................................................................................................................................. 71 2.0. Materials and methods ................................................................................................................................. 72 4.0. Data analysis ................................................................................................................................................ 76 5.0. Results ......................................................................................................................................................... 77 6.0 Discussion..................................................................................................................................................... 85 7.0. Conclusion ................................................................................................................................................... 88 Acknowledgements ............................................................................................................................................ 89 References .......................................................................................................................................................... 90 CHAPTER 5: ............................................................................................................................................................ 92 INFLUENCE OF SOIL TEMPERATURE ON DITYLENCHUS DESTRUCTOR AND DITYLENCHUS DIPSACI POPULATION DENSITY AND THEIR IMPACT ON POTATO TUBER DAMAGE ................................................................................... 92 Abstract .............................................................................................................................................................. 93 1.0. Introduction ................................................................................................................................................. 94 2.0. Materials and methods ................................................................................................................................. 95 3.0. Data analyses ............................................................................................................................................... 99 4.0. Results ......................................................................................................................................................... 99 6.0 Discussion................................................................................................................................................... 114 7.0 Conclusion .................................................................................................................................................. 116 Acknowledgements .......................................................................................................................................... 116 References ........................................................................................................................................................ 117 CHAPTER 6: .......................................................................................................................................................... 120 THE ENTOMOPATHOGENIC FUNGUS BEAUVERIA BASSIANA BENEFITS DITYLENCHUS DESTRUCTOR AND D. DIPSACI ON POTATOES .......................................................................................................................................... 120 Abstract ............................................................................................................................................................ 121 1.0 Introduction ................................................................................................................................................ 122 2.0. Materials and methods ..............................................................................................................................