Induction of drought tolerance in chickpea (Cicer arietinum L.) gown in sandy soil and modulation of plant metabolites as affected by PGR and PGPR

The plant growth promoting rhizobacteria (PGPR) can be implicated to utilize soils of low or marginal productivity for crop production. The present study was carried out to investigate the role of PGPR and PGRs (plant growth regulators) on the physiology of chickpea grown in sandy soil. The results showed that plants treated with consortium of PGPR and PGRS significantly enhanced the chlorophyll, protein and sugar contents. Highly significant increases (77%) were recorded for relative water content in PGPR and PGRs treated plants. Leaf proline content, lipid peroxidation and activities of antioxidant enzymes (CAT, APOX, POD and SOD) were increased in response to drought stress but decreased due to PGPR. Grain weight (41%), number of nodules (78%), pod weight (53%) and total biomass (54%) were higher in PGPR and PGR treated plants grown in sandy soil. Proline, L-arginine, L-histidine, L-isoleucine and tryptophan were accumulated in the leaves of chickpea exposed to drought stress. Consortium of PGPR and PGRs induced significant accumulation of riboflavin, L-asparagine, aspartate, glycerol, nicotinamide, and 3-hydroxy-3-methyglutarate in leaves of chickpea. Sensitive genotype showed significant accumulation of nicotinamide and 4-hydroxy-methylglycine in PGPR and PGR treated plants at both time points (44 and 60 days) as compared to non-inoculated drought plants. Arginine accumulation was also enhanced in the leaves of sensitive genotype under drought condition. Based on classical univariate and multivariate ROC curve analysis, thirteen metabolites with high AUC values (Area under receiver operating characteristic (ROC) curve, 0.964) were identified as potential biomarkers for drought tolerance. Integrative use of consortia of PGPR and SA appears to be an effective eco-friendly approach to induce drought tolerance in crop plants.