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Oral: Schroth Faces of the Future Symposium: Epidemiology and Management


Fungicide stress induces genome mutation in Sclerotinia sclerotiorum.
S. EVERHART (1), B. Amaradasa (1) (1) University of Nebraska, U.S.A.

Exposure to low levels of fungicides may generate stress that results in genomic mutations that may be an important source of variation for clonal populations. We tested this hypothesis using the clonal pathogen, Sclerotinia sclerotiorum. Eight wild-type isolates were exposed to five fungicides with different modes of action: boscalid, iprodione, thiophanate methyl, azoxystrobin and pyraclostrobin. Mycelium was grown on a logarithmic fungicide gradient and sub-cultured from the 50-100% inhibition zone for 12 consecutive generations. A selection of fungicide-exposed isolates (n=17) showing mutations at SSR loci were selected for further analysis, in addition to pre-exposure (n=8) and non-exposed control isolates after 12 generations on PDA (n=8). Amplified fragment length polymorphism (AFLP) analysis was performed using three primers and resulted in a set of 602 polymorphic alleles. Cluster analysis with PCoA and DAPC showed fungicide-treated isolates formed a distinct group from pre- and non-exposed control isolates (PhiPT=0.151, P=0.001). Dendrograms based on neighbor-joining also supported allelic variation associated with treatment groups, where a single cluster with high bootstrap support (60.7%) included 12 of 17 fungicide-exposed isolates. Collectively, this work will aid our understanding how non-lethal fungicide exposure may affect genomic variation, which may be an important mechanism for adaptation and evolution of clonal organisms.