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Poster: Epidemiology: Population Biology Genetics


Spatial and temporal structure of Sclerotinia sclerotiorum in New York State
A. DUNN (1), J. Kikkert (2), S. Pethybridge (3) (1) Hobart and William Smith Colleges, U.S.A.; (2) Cornell Cooperative Extension, Cornell Vegetable Program, U.S.A.; (3) Cornell University, U.S.A.

Sclerotinia sclerotiorum causes white mold on many vegetable and field crops in New York State, but the population structure has not been thoroughly studied. To assess spatial and temporal variation of S. sclerotiorum in New York State, 200 isolates were sampled from 10 bean fields in 2014, and 36 isolates were obtained from a historical collection (sampled from various hosts between 1982 and 2008). Isolates were genotyped using eight microsatellite loci. Mycelial compatibility group (MCG), in vitro growth rate, and aggressiveness on snap bean plants were also assessed for 22 selected isolates. Twenty-eight unique multilocus genotypes (MLGs) were identified (24 in 2014). One MLG represented 44 and 47 percent of isolates sampled in 2014 and prior to 2014, respectively. In 2014, genotypic diversity was low (3 to 8 MLGs per field) and Nei’s genetic diversity varied among fields (0.42 to 0.90). Analysis of molecular variance indicated no significant spatial structure within or between fields, and the index of association differed significantly from zero in all fields. Isolates of the same MCG almost always shared the same MLG. Growth rate and aggressiveness varied slightly but significantly among some isolates, but no significant association was found between the two measurements. Thus, the S. sclerotiorum population in New York State is highly clonal, and a small number of representative isolates would likely be sufficient to test new disease management strategies.