Effect of plant growth promoting rhizobacteria on the growth promotion of Mustard CS61 (Brassica juncea)

Abstract

Plant growth-promoting rhizobacteria (PGPR) help plants grow and develop by protecting them from abiotic and biotic stresses, thereby increasing biochemicals synthesis that promote growth and nutrients uptake. Soil salinity is a major global constraint on crop productivity, and salt-tolerant PGPR offer a promising mitigation strategy. This study represents the use of PGPR consortia in the growth and augmentation of Mustard CS61 (Brassica juncea) under saline conditions. 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 were obtained, of which 168 isolates were screened for halotolerance. Further on the basis of purity, morphological characteristics, and PGPR traits three isolates were selected. These isolates produced significant amounts of IAA with concentrations of 59.27–81.63 µg mL⁻¹, and prominent CMC activity with hydrolysis zones of 2–5 mm. Molecular identification by 16 S rRNA sequencing revealed the potential isolates as Micrococcus luteus (Accession No. PX974661), Microbacterium barkeri (Accession No. PX974662) and (Accession No. PX974663). Plant growth promotion studies with consortia on salt tolerant variety Mustard CS61 (Brassica juncea L.) under 1% saline conditions showed 100% germination, improved seedling vigour, and increased growth. Future studies using metagenomic approaches are needed to explore the wider uncultured microbial diversity, to discover novel genes associated with stress tolerance and plant growth–promoting traits.