Isolation, characterization, and evaluation of plant growth promoting rhizobacteria (PGPR) from rice rhizosphere of Nalgonda District, Telangana, India

Aims:The aim of this study was to isolate, characterize, and evaluate the plant growth-promoting traits and effects on rice seed germination of PGPR strains obtained from rice rhizosphere soil samples.Methodology and results: Three bacteria (PGPR-A, PGPR-B and PGPR-C) were isolated from Oryza sativa rhizosphere soil samples from different fields of Nalgonda district, Telangana, India, using a nutrient medium.Serial dilution of different rice rhizosphere soil samples was done to isolate the PGPR bacteria, and then subculturing of morphologically different isolates was done to purify the isolates.Out of eight pure isolates, three bacteria showed variable PGPR characteristics such as hydrogen cyanide (HCN) production, ammonia production, nitrogen fixation, IAA production and phosphate solubilization.Morphological, biochemical characterization and extracellular enzyme production were also performed on all three PGPR isolates, which gave varied results.Among these three isolates, PGPR-B is highly positive for HCN production.It showed positive results for ammonia production, nitrogen fixation and phosphate solubilization activity.IAA production was negative with all three PGPR bacteria.Out of three PGPR isolates, rice seeds incubated with the PGPR-B isolate showed enhanced seed growth.Hence, molecular identification was carried out to identify this bacterium.After DNA isolation and PCR reaction, the PCR product was used to determine its 16S rDNA sequence, which was submitted to NCBI, and its accession number was PP817225.It was 99.86% closely related to Bacillus tropicus strain MCCC 1A01406.Conclusion, significance and impact of study: Among three PGPR isolates (A, B and C), PGPR-B isolate showed more PGPR characteristics.Separate incubation of rice seeds with three PGPR isolates proved that PGPR-B as a potential isolate to increase rice seed growth than other two PGPR isolates (A and C).