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Plant Disease Management
Second I.E. Melhus Graduate Student Symposium: New Frontiers in Plant Disease Losses

The spatiotemporal genetic structure of Phytophthora capsici in Michigan and implications for disease management. K. H. LAMOUR and M. K. Hausbeck. Dept. Plant Pathology, Michigan State University, East Lansing, MI 48824. Phytopathology 91:S166. Publication no. P-2001-0133-SSA.

Phytophthora capsici isolates (3500) were hierarchically recovered from pepper and cucurbit hosts in Michigan from 1998 to 2000. All isolates were screened for compatibility type and mefenoxam sensitivity. Isolates (646) from seven locations were analyzed using AFLP markers and 70 percent (454) had unique AFLP profiles. Clonal reproduction was significant within years but no clones were recovered between years or locations. Populations had high levels of genetic diversity with 39 to 49 percent of the 94 possible AFLP bands polymorphic. Estimated heterozygosities ranged from 0.16 to 0.19. There was no correlation between genetic and geographical distance. The frequency of mefenoxam insensitivity did not decrease in insensitive populations tracked over two years without mefenoxam use. These data suggest that sexual reproduction plays a significant role in survival, maintaining genetic diversity, and the development of genetically diverse mefenoxam insensitive populations. The impact of these findings on current management strategies is discussed.