Identification and Frequencies of Endophytic Microbes within Healthy Grape Berries

Abstract

Intact, healthy grape berries were sampled from vineyards in the states of Washington and New York; in Tasmania, Australia; and from bunches of table grapes exported from Chile that were purchased on two occasions in a United States supermarket. Endophytic microbes were isolated on media conducive to fungi or bacteria and subsequently identified by Illumina sequencing of their DNA. Species of the yeast genera Metschnikowia, Pichia, and Hanseniaspora were recovered from every set of samples, as were species of the bacterial genera Acinetobacter, Burkholderia, Bacillus, Acetobacter, and Gluconobacter. Multiple other fungal and bacterial species were recovered less often. When quantified for the Washington samples and one set from the supermarket, non-Saccharomyces yeast species represented the vast majority of fungal identifications, while the distribution of various bacterial species varied widely between and within the two sources. The endophytic presence of these microbes within grape berries has implications with respect not only to the potential development of sour rot, but also to the broader concept of microbial terroir in wine quality.