Screening of Phosphate-Solubilizing and Potential Nitrogen-Fixing Bacteria from Apple Orchards in Karaman

The aim of this study was to isolate and molecularly identify bacteria capable of growing in nitrogen-free medium and solubilizing phosphate from apple orchard soil. Bacterial isolates were recovered from apple orchard soil, and those capable of growing on nitrogen-free medium and solubilizing phosphate were identified. Taxonomic identification of the isolates was performed based on sequencing of the V4 region of the 16S rRNA gene. A total of eight bacterial isolates capable of growing in nitrogen-free medium and 13 phosphate-solubilizing bacterial isolates were obtained. The isolates capable of growing in nitrogen-free medium were affiliated with the genera Pantoea, Streptomyces, Pseudomonas, Agrobacterium, Variovorax, and Rhizobium. The phosphate-solubilizing isolates were affiliated with the genera Pantoea, Enterobacter, Agrobacterium, Acinetobacter, Pseudomonas, Bacillus, Rhizobium, Streptomyces, and Sphingobacterium. Notably, Pseudomonas-related isolates represented a substantial proportion of the phosphate-solubilizing bacterial collection. The results indicate that apple orchard soil is a valuable source of bacteria with functional traits potentially associated with plant nutrient cycling. In particular, isolates capable of solubilizing phosphate and growing in nitrogen-free medium may represent promising candidates for further evaluation as plant growth-promoting microorganisms. These indigenous isolates could be further investigated for their potential use as microbial inoculants to support sustainable agricultural production.