Detection of actinobacteria from sediment soil: Exploration of metabolites as fungal plant pathogen inhibitors and plant growth promoters

The rhizosphere is an area with dense microbial activity. Actinobacteria are one among the rhizomicroflora inhabiting in the plant rhizosphere by protecting plants from pathogens by producing secondary metabolites, as plant growth promoters and by producing hydrolytic enzymes. But in the modern era of agriculture, the outrageous use of chemical fertilizers in the agriculture fields is causing major environmental pollution and the agricultural soil is losing its texture and fertility. So, in the present study, we aimed to isolate and screen indigenous actinobacterial strains which are capable of producing antifungal metabolites, plant growth promoting ability and hydrolytic enzymes. A total of 23 isolates of actinobacteria have been isolated. Among all the other actinobacterial isolates, Streptomyces sp. DRPG-15, which was isolated from the sediment soil of the Tamankal River, revealed a noticeable antagonistic activity against Macrophomina phaseolina for Sorghum and Sclerotium rolfsii for Chickpeas respectively. 16S rRNA sequence analysis showed that the Streptomyces sp. DRPG-15 exhibited 100% homology with Streptomyces enissocaesilis DRPG-15 OP985046. All 23 isolates were screened for the production of indole acetic acid, hydrogen cyanide, ammonia production and nitrate reduction and were also screened for various hydrolytic enzymes like Caseinase, Protease, Cellulase, Amylase, Chitinase, Pectinase, Gelatinase, L-asparaginase and Streptomyces sp. DRPG-15 was the only isolate that showed positive results for antagonistic activity, plant growth-promoting ability and enzymatic activity. The entire study indicates that the selected strain of Streptomyces sp. DRPG-15 is implying its possible utilization as a natural bioinoculant for sustainable agriculture.