Isolation and characterization of plant growth promoting actinobacteria, Amycolatopsis samaneae (AM75), from the rice rhizosphere in mirza area, Assam, India

This study aimed to isolate plant growth-promoting actinobacteria from the rhizosphere of rice. Rhizospheric soil samples were collected from the Aijung variety of rice in the Mirza area, Kamrup district, Assam, India. The isolate AM75 identified as Amycolatopsis samaneae, was characterized as gram-positive and non-motile. It exhibited varied colony characteristics on different selective media. The isolate produce several enzymes including urease, nitrate reductase, lipase, catalase, and amylase but did not demonstrate cellulase or gelatinase activity. Notably, isolate AM75 displayed various plant growth-promoting activities such as siderophore activity, hydrogen cyanide (HCN) production, indole-3-acetic acid (IAA) production, and zinc solubilization. However, it did not produce hydrogen sulfide (H2S) or solubilize phosphate. The optimal growth conditions for AM75 were pH 7.2, 30ºC temperature, and NaCl 2.5% concentration. Additionally, AM75 exhibited inhibitory activity against the plant pathogens Erwinia chrysanthemi ATCC11660, Aspergillus niger ATCC6275, and Fusarium oxysporum ATCC62506. The isolate was resistant to standard antibiotics, including rifampcin, streptomycin, ampicillin, and nalidixic acid.