P-544 - Genomic characterization and resistance implications for management of Botrytis cinerea populations in California nurseries

Botrytis cinerea is one of the most destructive and economically important diseases in California’s ornamental and vegetable transplant production. B. cinerea is considered the most recurrent pathogen in greenhouse-grown plants statewide, causing leaf spots, blights, stem cankers, and blossom rots. Growers heavily rely on fungicides to manage Botrytis diseases, but its persistence despite chemical control makes it a challenging pathogen. Botrytis is considered a high-risk pathogen for resistance; its populations can evolve fungicide insensitivity. Since 2021, 225 Botrytis isolates have been collected from 26 hosts (44% vegetable transplants and 56% ornamentals) across 16 California counties. Sanger sequencing in the G3PDH, RPB2, and HSP60 genes of representative isolates revealed B. fabae, B. californica and B. prunorum to be also present in the Botrytis collection. Using a low coverage whole genome sequencing approach, representative samples per year, host and location will be selected to characterize Botrytis populations at the genomic level. Results will determine if the Botrytis populations are structured based on location, host, or year of collection. In addition, mutations providing fungicide resistance to the fungicide mode of action will be identified per isolate and compared with fungicide phenotyping profiles currently underway. Characterization of Botrytis populations from nursery crops in California will provide improved management tools to producers.