Microbiota on almonds, cherry and peach trees in Apulia region

Stone fruits are economically important crops in Italy, particularly in the southern regions. Different diseases can affect them, and fungal and bacterial diseases cause significant economic losses by reducing yield and stone fruit production. A two-year study aimed to evaluate the epiphytic microorganisms present in buds, twigs, leaves, and fruits of almond, cherry, and peach trees from different mesoclimatic Apulian areas. Samples were collected during the growing seasons 2022-2023 and 2023-2024, from the end of March to June, and over 250 bacterial and yeast isolates were isolated. All were grouped into different morpho-molecular types. Considering the presence of all morphotypes for each sampling time, according to the multivariate analysis, significant differences (p>0.05) were observed between morphotypes, orchards, and ocations. Based on the biochemical characterization (KOH, fluorescence, LOPAT, and urease tests) performed on 52 isolates representing 14 morphotypes, 16 biochemical profiles were identified, generally corresponding to non-pathogenic bacteria and yeasts. The molecular analysis of the partial 16S rDNA sequences proved that Pseudomonas was the most represented genus (six morphotypes), followed by Curtobacterium, Sphingomonas, Rhodotorula (two morphotypes each), and Pantoea and Hannaella (one morphotype each). All of them are well known to include species with antimicrobial activity. In conclusion, the data provide valuable information on the epiphytic bacteria living on the aerial organs of Puglia's main stone fruit species. Furthermore, the isolated species can provide a useful collection of bacteria and yeasts to study for their antagonistic effects towards other organisms harmful to stone fruit.