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

Abstract

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 inhabitingVacciniumspp. nectar, as well as nectar volume and sugar concentrations, hypothesizing that nectar traits and microbial communities would vary between plants. We compared wildV. myrsiniteswith two field-grownV. corymbosumcultivars collected from two organic and two conventional farms. Differences in nectar traits and microbiomes were identified betweenV. corymbosumcultivars but notVacciniumspecies. 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, includingRosenbergiellasp. andSymmetrospora 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.One-sentence summaryParallel analysis of blueberry crops and a wild relative offers insight into the impacts of management and domestication on the nectar microbiome