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Poster: Epidemiology: Population Biology Genetics


Short-term Host Selection Pressure Has Little Effect on the Evolution of Verticillium dahliae
K. PURI (1), S. Gurung (1), D. Short (2), G. Sandoya (3), R. Hayes (4), K. Subbarao (1) (1) University of California, U.S.A.; (2) Division of Plant and Soil Sciences, West Virginia University, U.S.A.; (3) UC Davis Genome Center, U.S.A.; (4) United States

Understanding pathogen evolution over time is vital for breeding and deployment of host resistance. To study this in the context of a soilborne pathogen, within-field population structure from three major hosts (spinach, tomato and lettuce) and the potential of host-directed evolution of V. dahliae race 1 were determined. A total of 408 representing 192, 44, and 172 isolates from spinach, tomato and lettuce, respectively, were collected from WA and CA. An additional 411 isolates were recovered over five years from an experimental screening plot infested with a race 1 strain in Salinas, CA. Isolates were genotyped using 13 microsatellite loci, race and mating type-specific primers. Results indicated no significant variation among the within-field populations from the three hosts. Isolates recovered from the screening plot over five years revealed no demonstrable changes in the race, species composition and mating type structure, except for six SSR locus variants. Replicated virulence assays of these six variants with the wild type race 1 strain on susceptible and resistant lettuce differentials suggested no significant virulence differences between them. This suggests that the deployed host resistance will remain stable against the native V. dahliae population, unless novel pathogen genotypes are introduced into the system.