Relationship between soil composition, diversity and antifungal properties of Bacillus spp. isolated from southeastern Anatolia

Abstract

This study examined the ecological properties, 16S rRNA definition and in vitro antagonistic effect of Bacillus spp. against Alternaria spp., Aspergillus flavus, Pseudocercospora pistacina and Septoria sp., which are destructive pathogens of pistachio nut. Bacillus spp. were isolated from rhizosphere soil samples of mined borderlines (Area I), naturally growing pistachio areas (Area II), and pistachio orchards applying standard/conventional agricultural practices (Area III). A total of 106 Bacillus spp. were isolated and 11 taxa were defined through 16S rRNA sequence analyses. Canonical correspondence analysis (CCA) was used to examine the relationship between Bacillus species and environmental variables including macro- and micro-elements, physical and chemical properties of the soil samples. The highest antagonistic activity was exhibited by B. amyloliquefaciens, B. atrophaeus, B. subtilis, B. licheniformis, and B. pumilus strains isolated from area I. Furthermore, antagonistic B. pumilus, B. mycoides, and B. amyloliquefaciens strains showed tolerance to Zn and Mn indicated by CCA. To the best of our knowledge, this is the first report on determination of alternative biological control agents and their possible use in integrated pest management strategies in pistachio orchards.