Variation in growth and ion uptake of maize due to inoculation with plant growth promoting rhizobacteria under salt stress

Soil salinity decreases plant growth and photosynthetic activity besides resulting in nutrient imbalance in plants. Plant growth promoting rhizobacteria (PGPR) can induce plant tolerance to salinity by producing various hormones and enhancing the availability of nutrients from soil matrix. A pot study was conducted to evaluate the effect of different PGPR strains on maize growth and ions uptake under salt stress conditions. Three salinity levels (4, 8 and 12 dSm-1) along with original EC were maintained in the pots using NaCl salt. Maize seeds inoculated with pre-selected strains (S5, S15 and S20) along with uninoculated control were sown in the pots. Recommended doses of NPK were applied. In general, maize growth was decreased with the increase in salinity. Results indicated that PGPR inoculation, even at higher EC (12 dS m(-1)), significantly increased shoot/root fresh weight, shoot/root dry weight, chlorophyll a, b and cartenoid contents upto 64/114, 102/102, 154, 102 and 58%, respectively, compared with un-inoculated control. Similarly, inoculation restricted the uptake of Na+/Cl-ions and enhanced the accumulation of N, P and K in shoot compared to control. Among the three selected strains, S20 performed better at all EC levels. The growth promotion and increased ions uptake exhibited by strain S20 might be due to its high in vitro IAA production, chitinase activity, P-solubilition and more intensive root colonization, besides ACC-deaminase activity.