Multifaceted impact of Bradyrhizobium sp. bacteria in enhancing the growth and resilience of Vigna mungo genotypes under fluoride stress

Abstract

Agricultural produce has been declining owing to variety of factors, fluoride being one of them is known for its phytotoxic effects. Thus, this study was carried out to investigate the potential of a N2 fixing bacteria, specifically Bradyrhizobium spp., in providing relief against the fluoride-mediated toxicity in Vigna mungo varieties. For the scope of study two varieties namely Vigna mungo L. cultivar KPU 405 (Mukundra urd-2) and PRATAP URD 1(KPU 07-08) were considered. Preliminary pot study was conducted to access fluoride resistance capability of both genotypes. Seeds of both cultivars were sown in soil spiked with varied NaF concentration (0, 10, 20, 30 and 40 ppm). Additionally pots were inoculated with Bradyrhizobium spp. in form of a suspension culture, at the 15th day of germination having 160 μmol quanta m−2 s−1 of photon density, 16-h photoperiod, and 50–60% relative humidity at 28 ± 2 °C. Phytotoxicity of fluoride was observed in terms of oxidative stress among all pots supplied with fluoride while pots with treatment of Bradyrhizobium spp. provide reinforcement across all pots among all sets including control groups. The beneficial impact of microbial inoculation was determined based on of different physiological as well as bio-chemical tests including plant biomass, plant height, tolerance index, relative water content, Chl a, chl b and total chl content, decreased the MDA and increased the antioxidant defence system. Interestingly, Bradyrhizobium sp. was able to act antagonistically to fluoride stress in both the Vigna mungo varieties. The present study concluded that soil application of Bradyrhizobium spp. can be a useful approach in protecting Vigna mungo from fluoride toxicity.