A quantitative survey of the blueberry (Vaccinium spp.) nectar microbiome: variation between cultivars, locations, and farm management approaches

Microbes in floral nectar can impact both their host plants and floral visitors, yet little is known about the nectar microbiome of most pollinator-dependent crops. In this study, we examined the abundance and composition of the fungi and bacteria inhabiting Vaccinium spp. nectar, as well as nectar volume and sugar concentrations, hypothesizing that nectar traits and microbial communities would vary between plants. We compared wild V. myrsinites with two field-grown V. corymbosum cultivars collected from two organic and two conventional farms. Differences in nectar traits and microbiomes were identified between V. corymbosum cultivars but not Vaccinium species. The microbiome of cultivated plants also varied greatly between farms, whereas management regime had only subtle effects, with higher fungal populations detected under organic management. Nectars were hexose-dominant, and sugars were depleted in nectar with higher cell densities. Bacteria were more common than fungi in blueberry nectar, although both were frequently detected and co-occurred more often than would be predicted by chance. Cosmopolitan blueberry nectar microbes that were isolated in all plants, including Rosenbergiella sp. and Symmetrospora symmetrica , were identified. This study provides the first systematic report of the blueberry nectar microbiome, which may have important implications for pollinator and crop health. ### Competing Interest Statement The authors have declared no competing interest.