Characterization of fruit carposphere bacterial communities during harvest

Assessing the microbes present on fruit carpospheres as the fruit enters postharvest processing could have useful applications, as these microbes could have a major influence on spoilage, food safety, verification of packing process controls, or other aspects of processing. The goal of this study was to establish a baseline profile of bacterial communities associated with apple (pome fruit), peach (stone fruit), and Navel orange (citrus fruit) at harvest. We found that commercial peaches had the greatest bacterial richness followed by oranges and finally apples. Only oranges and peaches had significant changes in bacterial diversity depending on the time they were harvested. The observed shifts in diversity varied by fruit type, where 70% of the variability in beta diversity on the apple carposphere was driven by the gain and loss of species (i.e., nestedness). The peach and orange carposphere bacterial community shifts were driven by nearly an even split between turnover (species replacement) and nestedness. We identified a small core microbiome for apples and peaches, and a relatively diverse core microbiome for oranges. Overall, our findings illustrate the important temporal dynamics of bacterial communities found on major commercial tree fruit, and we discuss their implications entering postharvest packing and processing.