Plant growth promotion activities of Bacillus spp. isolated from Jakrem hot water spring of Meghalaya, North East India

Abstract

The study aims to investigate plant growth promotion (PGP) activities of thermophilic bacteria isolated from the Jakrem hot spring in Meghalaya, North-East India, and determine their effect on Brassica juncea's growth. The bacteria were isolated by a culture-dependent approach following a serial dilution method in a nutrient agar medium. All the isolates were determined for PGP attributes such as indole acetic acid, phosphate solubilization, hydrolytic enzymes, and siderophore production. The potent bacterial isolates were characterized by 16S rDNA sequencing and phylogenetic analysis. Altogether, 53 bacterial isolates were obtained, most belonging to the genus Bacillus. Of the total isolates, 37.7% exhibited both PGP and hydrolytic enzyme activities. Three isolates, namely JAB1, JAB8, and JAB100, showed promising PGP and were identified as Bacillus velezensis, B. proteolyticus, and Bacillus sp., respectively. The PGP attributes of these isolates were determined in vivo on B. juncea, and their effects were measured in terms of shoot and root length biomass and biochemical contents. It was observed that combined inoculation of all three isolates significantly enhanced the growth and development of B. juncea, evident by increased shoot and root length, fresh and dry weight, and higher levels of protein, phenol, flavonoid, and chlorophyll content compared to the control. In conclusion, the study highlights the potential application of thermophilic Bacillus spp. from hot springs as bioinoculants to enhance crop productivity in sustainable agricultural practices.