Spatiotemporal Distribution and Anti-Verticillium Activity of the Endophytic Bacterial Microbiome in Wild Almonds (Amygdalus spp.) of the Central Zagros Mountains of Iran

Abstract

Wild almond (Prunus, subgenus Amygdalus) species host a diverse array of endophytic bacteria with biological activities. Zagros Mountains of Iran are home to various almond wild species. However, there is little information on the diversity and bioactivity of endophytic microorganisms in wild plants in these areas. Here, spatiotemporal distribution of endophytic bacteria in the healthy tissues (leaf, root, trunk and fruit) of several Amygdalus wild species, including A. eleagnifolia, A. arabica, A. haussknechtii and A. scoparia were investigated in the area. Over 100 strains were isolated, primarily from the Bacillus and Stenotrophomonas genera. An antifungal screening targeting the almond's fungal pathogen Verticillium dahliae, identified 14 superior bacterial strains, that is, Bacillus sp., subtilis group (B33, B63, B7, B85 and B101), Bacillus mojavensis (B90 and B16), Bacillus thuringiensis (B32 and B40), Bacillus mycoides (B74), Bacillus altitudinis (B72), Bacillus velezensis (B35), Bacillus licheniformis (B41) and Stenotrophomonas maltophilia (B5). The predominant species was Bacillus sp., subtilis group, which constituted 35.71% of the superior strains. These strains demonstrated notable antifungal properties against V. dahliae, both in dual-culture assays and though the emission of volatile organic compounds. Accordingly, this study provides the first documentation of the wild almonds' bacterial microbiome diversity in central Zagros Mountains of Iran, and its potential for biological disease control in organic farming systems.