Pollinator Visitation Alters Cranberry Flower Fungal Communities in Wisconsin Cranberry Agroecosystems

Pollinators are known dispersal agents of microbial communities between flowering plants, although the role of insect-mediated microbial assembly in flowering agricultural crops is not well understood. In cranberry (Vaccinium macrocarpon Ait.) agroecosystems, the blossom period is a vulnerable time for infection from pathogens within the cranberry fruit rot fungal disease complex, and understanding the components and assembly dynamics in cranberry flower fungal communities may provide important insights to the relationship between the cranberry microbiome and crop health. This 2-year study uses a combination of culture-dependent and next-generation sequencing approaches to compare the community structure of cranberry flowers, honey bees (Apis mellifera), bumble bees (Bombus sp.), wild solitary bees, hover flies (Syrphidae), and nearby wildflowers to identify shared fungal associates. Compared to a tenting treatment in cranberry flowers used to prevent insect visitation, cranberry flowers with access to pollinators have higher detection of fungal genera in culture, as well as more fungal genera identified through culture-independent methods. Fungi associated with the cranberry fruit rot complex were identified in several insect groups, with the highest proportion of identified fruit rot fungi detected in Toxomerus fly samples. This research provides the first evidence of shared fungal communities between pollinators and managed cranberry flowers.