Highbush blueberry (Vaccinium corymbosum) is an economically important fruit-bearing woody perennial. Despite the importance of microbial communities to plant health, the aboveground (phyllosphere) microbiome of blueberry is understudied. The phyllosphere is exposed to varying conditions throughout a growing season. The fruit undergoes extensive physiological change across a season from bud to fruit. This study aimed to provide a temporal characterization of the blueberry phyllosphere across a growing season and a characterization of specific tissues and phenological stages. Blueberry branches were harvested every other week across 2 years and two locations during the development process of the blueberry fruits. The internal transcribed spacer regions were amplified from DNA extracts and sequenced to perform amplicon-based characterization of the fungal microbiome across time and plant tissue. Fungal communities showed changes in α-diversity depending on the week of harvest and tissue type. Early in the season, α-diversity was high, but it decreased in midseason when flowers developed into fruit. Later in the season, as the fruit ripened, α-diversity increased again. The β-diversity of the community changed across time and tissue types during plant development. Notable members of the identified core microbiome were members of the genus Alternaria, Peltaster, and Taphrina, as well as the pathogenic taxa Aureobasidium pullulans and Botrytis cinerea. This research provides background for future experimentation of understanding the microbial composition in the blueberry phyllosphere in relation to the infection court of pathogens (e.g. Colletotrichum fioriniae and B. cinerea) and the temporal components of blueberry plant health and management.

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