.................................................................................................................................. iii ACKNOWLEDGMENTS .............................................................................................................. v DEDICATION ............................................................................................................................... vi LIST OF TABLES ......................................................................................................................... ix LIST OF FIGURES ........................................................................................................................ x LIST OF APPENDIX TABLES ................................................................................................... xii CHAPTER I. LITERATURE REVIEW ......................................................................................... 1 The Potato ............................................................................................................................1 The Disease ..........................................................................................................................4 Causal Organism ..................................................................................................................9 Environmental Conditions Conducive for Disease Development .....................................16 Management Approaches...................................................................................................22 Literature Cited ..................................................................................................................27 CHAPTER II. FIELD EVALUATION OF POTATO GENOTYPES FOR RESISTANCE TO POWDERY SCAB ON TUBERS AND ROOT GALL FORMATION CAUSED BY SPONGOSPORA SUBTERRANEA ............................................................................................... 38 Abstract ..............................................................................................................................38 Introduction ........................................................................................................................39 Materials and Methods .......................................................................................................42.............................................................................................................................38 Introduction ........................................................................................................................39 Materials and Methods .......................................................................................................42 Results ................................................................................................................................47 Discussion ..........................................................................................................................60 Literature Cited ..................................................................................................................63