Bacterial endophytes of rice (Oryza sativa L.) and their potential for plant growth promotion and antagonistic activities

Abstract

Bacterial endophytes live inside the plant tissues and known to play a crucial role in the functioning of host plants through influencing their physiology and development. In present study, a total of 32 bacterial endophytes were isolated from four plant tissues (root, stem, leaf and grain) of six rice varieties cultivated in central-eastern and northeastern states of India. Microbial composition varied among the plant tissues studied, they were predominant in the root and leaf tissues. Biochemical and molecular characterization identified these bacterial isolates belonging to phyla Proteobacteria and Firmicutes representing 5 genera. Out of 32 isolates, (19) 59.3% Gram's stain-positive, (17) 53.1% were able to produce indole acetic acid, (9) 28.1% siderophore development and (18) 56.2% phosphate solubilization activities indicating the plant growth-promoting (PGP) ability. The antagonistic activity of identified bacterial endophytes was determined against bacterial leaf blight disease-causing pathogen, Xanthomonas oryzae pv. oryzae (8 isolates) and soilborne fungal pathogens viz, Rhizoctonia solani (17 isolates), Fusarium verticillioides (15 isolates) and Sclerotium rolfsii (9 isolates) were exhibiting antagonistic activities against tested pathogens. Further, to confirm the probable role of lipopeptides in antagonism, PCR based detection of lipopeptide genes in the genome of bacterial endophytes showed the presence of antibacterial (surfactin) and antifungal (iturin D and bacillomycin D) genes in Bacillus subtilis (NIBSM_OsR10). This Bacillus subtilis isolate showed potential antibacterial activities against Xanthomonas oryzae pv. oryzae and strong antagonistic activities against fungal pathogens Rhizoctonia solani, Fusarium verticelloides and Sclerotium rolfsii. Potential isolates exhibiting antibacterial and antifungal activities in the present study may be used for the development of biocontrol formulations for controlling multiple biotic stresses.