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

Authors: Rering, Caitlin; RUDOLPH, ARTHUR - Former ARS Employee; Li, Qin-Bao; Read, Quentin; MUNOZ, PATRICIO - University Of Florida; TERNEST, JOHN - University Of Florida; Hunter, Charles

Submitted to: bioRxiv
Publication Type: Pre-print Publication
Publication Acceptance Date: 9/12/2023
Publication Date: 9/12/2023
Citation: Rering, C.C., Rudolph, A.B., Li, Q., Read, Q.D., Munoz, P.F., Ternest, J.J., Hunter Iii, C.T. 2023. A quantitative survey of the blueberry (Vaccinium spp.) nectar microbiome: variation between cultivars, locations, and farm management approaches. bioRxiv. https://doi.org/10.1101/2023.09.11.556904.
DOI: https://doi.org/10.1101/2023.09.11.556904

Interpretive Summary: Microorganisms such as yeast and bacteria are often found growing in the nectar of flowers. These microbes can affect the health of the plants they colonize and the pollinators that drink floral nectar. Despite their importance to plant and pollinator health, nectar microbes present of many crops have not been well-studied. ARS Scientists at the Center for Medical, Agricultural, and Veterinary Entomology, in Gainesville, FL in collaboration with scientists from University of Florida collected nectar from blueberry flowers to investigate nectar microbial communities. Blueberry is a nutritious and valuable crop that needs pollinators in order to produce fruit. Flowers were collected from organic and conventional farms as well as from a wild blueberry species growing in nature preserves. In all nectar samples, the microorganisms, volume, and sugar concentration were measured. Microorganisms were found in approximately 2/3 of flowers. The number and type of nectar microorganisms differed between blueberry varieties. Nectar sugars and volumes also differed between plants. Organic farms had slightly higher concentrations of fungi and yeast than conventional farms, which may be explained by the use of fungicides. By better understanding the microorganisms that inhabit the nectar of crop flowers, we can begin to study their effects on plants and pollinators, whether these effects are neutral, negative, or positive. Results from this study will help promote the growth of beneficial microorganisms that protect plants and pollinators, thereby promoting a safe and sustainable food supply.

Technical 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 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.