Drought stress adversely affects the growth and yield of wheat. The present study was planned to investigate the effect of inoculation of plant-growth promoting rhizobacteria (PGPR) strains IG 3 (Klebsiella sp.), IG 10 (Enterobacter ludwigii) and IG 15 (Flavobacterium sp.) in improving drought tolerance in wheat. These PGPR strains were screened for drought tolerance in nutrient broth supplemented with different concentrations (0-25%) of polyethylene glycol (PEG6000). Effect of PGPR inoculation on various physiological, biochemical parameters and gene expression of stress responsive genes were studied under drought stress. Root colonization at the surface and interiors of roots was demonstrated using scanning electron microscopy (SEM) and tetrazolium staining, respectively. Drought stress significantly affected various growth parameters, water status, membrane integrity, osmolyte accumulation and stress-responsive gene expressions, which were positively altered by PGPR-inoculation in wheat. Quantitative real-time (qRT)-PCR analysis revealed the up regulation of some stress-related genes (DREB2A and CAT1) in un-inoculated wheat plants exposed to drought stress. PGPR-inoculated plants showed attenuated transcript levels suggesting improved drought tolerance due to interaction of PGPRs. The PGPR strain IG 3 was found to be the best in terms of influencing biochemical and physiological status of the seedlings under drought stress. Our report demonstrates the role of PGPRs Enterobacter ludwigii and Flavobacterium sp. in plant growth promotion of wheat plants under drought stress. The study reports the potential of PGPR in alleviating drought stress in wheat which could be used as potent biofertilizers.

Plant growth and yield is adversely affected by soil salinity. Salt tolerant plant growth-promoting rhizobacteria (PGPR) strain IG 3 was isolated from rhizosphere of wheat plants. The isolate IG 3 was able to grow in presence of NaCl ranging from 0 to 20% in Luria Bertani medium. The present study was planned to evaluate the role of inoculation of PGPR strain IG 3 and its efficacy in augmenting salt tolerance in oat (Avena sativa) under NaCl stress (100mM). The physiological parameter such as shoot length, root length, shoot dry weight, root dry weight and relative water content (RWC) were remarkably higher in IG 3 inoculated plants in comparison to un-inoculated plants under NaCl stress. Similarly, the biochemical parameters such as proline content, electrolyte leakage and malondialdehyde (MDA) content and activities of antioxidant enzymes were analyzed and found to be notably lesser in IG 3 inoculated oat plants in contrast to un-inoculated plants under salt stress. Inoculation of IG 3 strain to oat seedlings under salt stress positively modulated the expression profile of rbcL and WRKY1 genes. Root colonization of root surface and interior was demonstrated using scanning electron microscopy and tetrazolium staining, respectively. Due these outcomes, it could be implicated that inoculation of PGPR strain IG 3 enhanced plant growth under salt stress condition. This study demonstrates that PGPR play an imperative function in stimulating salt tolerance in plants and can be used as biofertilizer to enhance growth of crops in saline areas.

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Soybean (Glycine max (L) Merrill) is used in India mostly as a substantial fund of protein and oil, which makes the crop significantly important. Somaclonal variation has been researched as a base of additional variability for drought in soybean. In the present experiment calli/cell clumps/embryoids rose from immature and mature embryonic axis and cotyledons explants were exposed to different concentrations of polyethylene glycol (PEG6000). A discontinuous method proved to be superior as it permitted the calli/embryoids/cell clumps to regain their regeneration competence. A total of 64 (12.21%) plantlets of genotype JS335 and 78 (13.13%) of genotype JS93-05 were regenerated after four consequent subcultures on the selection medium with an effective lethal concentration of 20% PEG6000, and proliferated calli/embryoids/cell clumps were further subcultured on Murashige and Skoog regeneration medium supplemented with 0.5 mgL−1 each of α-napthalene acetic acid (NAA), 6-benzyladenine (BA) and Kinetin (Kn), 20.0 gL−1 sucrose and 7.5 gL−1 agar. Putative drought-tolerant plantlets were acquired from genotype JS93-05 (38) in more numbers compared to genotype JS335 (26). Random decamer primers confirmed the presence of variability between mother plants and regenerated plants from both the genotypes. Since these plantlets recovered from tolerant calli/embryoids/cell clumps selected from the medium supplemented with PEG6000, the possibility exists that these plants may prove to be tolerant against drought stress.

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