Poster Session: Systematics/Evolution/Ecology-Fungi

32-P

Genetic analysis of worldwide Sclerotinia homoeocarpa populations with mating type and microsatellite markers.
A. PUTMAN (1), I. Carbone (1), L. Tredway (2)
(1) North Carolina State University, Raleigh, NC, U.S.A.; (2) Syngenta Crop Protection, Raleigh, NC, U.S.A.

Sclerotinia homoeocarpa causes dollar spot, the most economically important disease of turfgrass worldwide, but little is known about the population biology of this fungus. The objective of this research is to infer the population structure of S. homoeocarpa on a global scale. We performed genotyping at 14 microsatellite loci and determined mating type with a multiplex PCR assay. A total of 512 S. homoeocarpa isolates obtained from 43 locations on five continents and Oceania have been evaluated to date. Bayesian clustering analysis revealed limited admixture and clearly defined population structure between C3 and C4 host type isolates, with each type having two distinct groups. Within each type, some isolates assigned to the same group, and in select cases belonging to identical multilocus haplotypes, originated from multiple continents. A population sample from Puerto Rico formed a separate group that did not associate with isolates from either C3 or C4 grasses. Within each of 91 multilocus haplotypes, all isolates were of the same mating type. Clone correction showed that MAT1-1 and MAT1-2 were equally distributed among isolates from North America. Outside of North America the MAT1-1:MAT1-2 distribution was approximately 1:2, but this deviation was not significantly different from 1:1. Initial results from this research suggest that Sclerotinia homoeocarpa has undergone long distance dissemination, sexual reproduction, and clonal amplification.