P-556 - Dynamics and diversity of fungal species associated with strawberry and nearby weeds

Abstract Text: Weeds in strawberry fields may act as reservoirs for fungal pathogens influencing disease epidemiology. The primary aim of this study was to investigate the seasonality of fungal communities in strawberries and nearby weeds. During 2023 and 2024, a total of 1,117 fungal isolates were collected from strawberry plants and weeds nearby. Species of Colletotrichum, Alternaria, Botrytis, Fusarium, and Epicoccum were found to be commonly present in both hosts, representing over 900 isolates. Species prevalence varied depending on environmental conditions and/or plant growth stages. Intriguingly, weeds collected from multiple time points were all found to harbor well-known pathogens, including Botrytis and Colletotrichum. However, those pathogens were undetected in weed samples from non-strawberry fields, indicating the pathogens may first spread from strawberry plants to weeds. In addition, Colletotrichum nymphaeae, the causal agent of strawberry anthracnose, was frequently isolated from both hosts in multiple fields during 2018 to 2023. Whole-genome sequences of 45 C. nymphaeae isolates revealed 4 population clusters, with 3 clusters comprising isolates from strawberries and weeds. Our results further support the role of weeds as fungal reservoirs, implying weed management practices need to be unconducive to the release of strawberry pathogens during the growing season.