جداسازی باکتری‏های جنس استرپتومایسس از ریزوسفر برخی گیاهان زراعی و بررسی توان آن‏ها در کنترل قارچ Macrophomina phaseolina

Soil serves as a significant reservoir of beneficial microorganisms, particularly actinomycetes. These microorganisms are renowned for their capacity to produce secondary metabolites and biologically active compounds. Notably, actinomycetes are responsible for the production of approximately 75% of all known antibiotics, underscoring their critical role in biological control. The genus Streptomyces, which comprises Gram-positive, aerobic, and filamentous bacteria, is particularly noteworthy for its application in biological pest control. The present study aimed to isolate bacteria of the genus Streptomyces from the rhizosphere of various agricultural crops and to evaluate their potential in controlling Macrophomina phaseolina, a necrotrophic plant pathogen that infects over 500 economically significant plant species. To achieve this, soil samples were collected from a depth of 20 to 25 cm. The bacterial isolates were then screened and identified based on their morphological traits and through the use of PCR molecular identification methods employing general primers specific to the genus Streptomyces. The inhibitory efficacy of the collected isolates against the pathogenic fungus M. phaseolina was assessed. Isolates demonstrating an inhibitory effect greater than 80% were selected for further detailed identification. Subsequent analysis, including 16S rDNA region sequencing and various biochemical tests, revealed that the selected isolates were highly likely (with a probability of 99%) to belong to the species S. xanthophaeus, S. zaomyceticus, S. badius, and S. spororaveus. These findings highlight the potential of Streptomyces species as effective biological control agents against M. phaseolina, offering a promising avenue for the development of sustainable agricultural practices.