P-126 - Selection and molecular basis of fungicide resistance in Botrytis species from strawberry fields

Gray mold, caused by Botrytis species, is a critical fungal disease affecting the strawberry crop. The disease is mainly managed through frequent fungicide applications, inevitably leading to resistance development. In this study,1222 Botrytis isolates from northeastern and California strawberry fields were tested for resistance to commonly used fungicides, followed by the investigation of resistance mechanisms. Isolates from California strawberry fields seemed to have higher resistance frequencies than those from the northeastern states, with New York isolates exhibiting the lowest resistance frequencies. Further analysis showed significantly higher chemical class resistance (CCR) associated with isolates collected from plasticulture strawberries than matted-row strawberries. In addition, phenotypic and genotypic analysis of Botrytis isolates revealed two prevalent Botrytis species, including B. cinerea and B. fragariae. Using genome-wide association studies (GWAS), we identified significant single nucleotide polymorphisms (SNPs) related to fludioxonil resistance, located in a C6 transcription factor gene of B. fragariae. CRISPR/Cas9 is underway to validate the impact of this SNP on the fungicide sensitivity. Fludioxonil has been commonly used to control not only Botrytis but also Colletotrichum and the newly emerging disease Neopestalotiopsis. Our results reemphasized the importance of resistance management and discovered a possible novel mechanism underlying the highest level of resistance to fludioxonil in B. fragariae from strawberry fields.