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Investigation of Genotypes and Fungicide Resistance Profiles of Botrytis Populations on Single Strawberry Flowers

Mengjun Hu: University of Maryland

<div>Genotypic variation often can be found in fungal pathogens from different hosts, locations, and different parts of the same plant. However, information about pathogen diversity in single flowers has not been studied in depth. A total of 192 single-spore <em>Botrytis</em> spp. isolates obtained from 19 strawberry flowers were fingerprinted using microsatellite markers. Multiple haplotypes were found in 12 flowers, but seven flowers exhibited a single haplotype. Two different <em>Botrytis</em> species, <em>B. cinerea</em> and <em>B. fragariae</em>, were found co-existing in three flowers. Sensitivity was determined to the fungicides cyprodinil, fludioxonil, fenhexamid, iprodione, thiophanate-methyl, boscalid, fluopyram, penthiopyrad, and isofetamid, which represent six different chemical classes. Multifungicide resistance was commonly observed in both species but resistance to boscalid and penthiopyrad was detected only in <em>B. cinerea</em>. Isolates from the same flower, regardless of haplotypes, tended to have identical resistance profiles. Each haplotype was largely associated with a single resistance profile but a single resistance profile was often represented by multiple haplotypes. This study is the first to investigate genotypic and phenotypic diversity in <em>Botrytis</em> spp. isolated from the same tissue. The findings improve our understanding of epidemiology for <em>Botrytis</em> and may be relevant to genotyping and phenotyping studies in other fungal pathogen systems.</div>