Effect of plant growth promoting rhizobacterial consortia on growth promotion of Mustard CS61 (Brassica juncea)

Plant growth-promoting rhizobacteria (PGPR) helps plants grow and develop by protecting them from abiotic and biotic stresses, increasing the synthesis of biochemicals that promote growth, and enabling the uptake of nutrients. Salinity is one of the biggest problems throughout the world. The identification of novel, salt-tolerant PGPR offers a promising strategy to mitigate the adverse effects of soil salinity. This study aimed to isolate and characterize PGPR strains from mangrove rhizosphere soils collected from Koparkhairane (19.1045° N, 73.0033° E) to Belapur (19.0168° N, 73.0455° E), Navi Mumbai, Maharashtra, India. A total of 1,263 bacterial isolates obtained from the rhizospheric zone of mangroves, among which 168 isolates were selected for further screening, 10% isolates showed upto 8% NaCl tolerance. Further upon the basis of purity, morphological characteristics and PGPR traits such as indole acetic acid (IAA), phosphate solubilization, ammonia production, carboxymethyl cellulase, and protease activity three isolates were selected for further study. Molecular identification by 16S rRNA sequencing revealed the PGPR potential isolates as Micrococcus luteus (Accession No. CP001628) and Microbacterium barkeri (Accession No. X77446). Plant growth promotion studies with potential PGPR consortia on mustard CS61 (Brassica juncea L.) under 1% saline conditions showed 100% germination, improved seedling vigor, increased growth, and biomass compared to controls. This study represents the use of PGPR consortia in growth and augmentation of Mustard CS61 (Brassica juncea) under saline condition. Further studies using metagenomic approaches are needed to explore the wider uncultured microbial diversity, with the aim of discovering novel genes associated with stress tolerance and plant growth–promoting traits.