Terroir is the main driver of the epiphytic bacterial and fungal communities of mango carposphere in Reunion Island

The diversity of both bacterial and fungal communities associated with mango surface was explored using a metabarcodingapproach targeting fungal ITS2 and bacterial 16S (V3-V4) genomic regions. Fruits were collected in Reunion Island from twodifferent orchards according to a sampling method which allowed the effect of several pre-harvest factors such as geographicallocation (terroir), cultivars, fruit parts, tree position in the plot, fruit position on the tree (orientation and height), as well as theharvest date to be investigated. A total of 4,266,546 fungal and 2,049,919 bacterial reads were recovered then respectivelyassigned to 3,153 fungal and 24,087 to bacterial amplicon sequence variants (ASVs). Alpha and beta diversity, as well as differentialabundance analyses revealed variations in both bacterial and fungal communities detected on mango surfaces depended upon thestudied factor. Members of the Proteobacteria phylum were dominant and accounted for 84.77% of detected sequences for bacteriaand, followed by Actinobacteria (7.02%), Bacteroidetes (4%), Firmicutes (2.18%), Planctomycetes (0.47%) and Acidobacteria with0.41% of prevalence. As for fungal ASVs, members of the Ascomycota phylum (89.42%) were dominant in all samples, followed byBasidiomycota (10.55%), and Chytridiomycota (0,03%). For each studied location, mango fruit from each cultivar shared a coremicrobiome, and fruits of the same cultivar harvested in two different locations shared about 80% fungal and bacterial familytaxa. The various factors tested in this study affected bacterial and fungal taxa differently, suggesting that some taxa could act asgeographical (terroir) markers and in some cases as cultivar fingerprints. The ranking of the factors investigated in the presentstudy showed that in decreasing order of importance: the plot (terroir), cultivar, fruit parts, harvest date and the position of thefruits are respectively the most impacting factors of the microbial flora, when compared to the orientation and the fruit position(height) on the tree. Overall, these findings represent a breakthrough in current knowledge of the bacterial and fungalmicrobiome associated with the mango surface and its variations at the plot level.