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POSTERS: Fungicide and antibiotic resistance

Genomic alterations in Sclerotinia sclerotiorum after sub-lethal fungicide exposure
Nikita Gambhir - University of Nebraska. Sydney Everhart- Oregon State University, Zhian Kamvar- University of Nebraska

Fungicide resistance has been reported for 203 phytopathogenic fungi and poses a serious threat to fungicide efficacy. Understanding the genomic basis of resistance emergence can help to delay evolution of resistance. Sub-lethal fungicide dose exposure may stress plant pathogens to generate novel mutations, some of which may confer adaptive traits like fungicide resistance or aggressiveness. Previously, we exposed five progenitor isolates of S. sclerotiorum to sub-lethal doses of four fungicides (azoxystrobin, boscalid, iprodione, and thiophanate-methyl) for twelve consecutive generations. In this study, we sequenced pre- and post-exposure isolates (55 in total) and aligned the reads to the reference genome. We found that frequency of mutations did not increase with sub-lethal fungicide exposure but differed significantly according to the progenitor isolate (P-value < 0.05). About 47% of the genetic variation was explained by variation among isolates and 1% variation by sub-lethal fungicide exposure. High within-species variance may have masked the effect of fungicide exposure using the reference genome alignment. To address this, we will use de novo genome assembly tools for further analyses. Since sub-lethal fungicide exposure may confer traits like aggressiveness, greenhouse assays will be conducted to evaluate changes in aggressiveness. Results will expand our understanding about the role of sub-lethal fungicide dose in resistance emergence, which may be useful in designing strategies to delay resistance evolution and retain the efficacy of currently used fungicides.