Halotolerant rhizobacterial consortium confers salt tolerance to maize under naturally salt-affected soil

Halotolerant rhizobacteria, which are able to withstand higher concentrations of salts, are useful for conferring salinity tolerance to agricultural crops and improving soil fertility through their different activities. Among their various mechanisms, the improvement in soil enzyme activities they bring about through production of extracellular enzymes is crucial. Soil enzymes are responsible for supplying nutrients to plants under stressed conditions. In the current study, halotolerant plant growth-promoting rhizobacteria (Bacillus and Acinetobacter) species were examined individually and in combination to compare the efficiency with which they improve soil enzyme activities under naturally salt-affected soil conditions. The microbial consortium caused a significant increase in the soil urease (1.15-fold), dehydrogenase (14%), acid phosphatase (78%), and alkaline phosphatase (52%) activities, which led to a significant increase in shoot N (42%), grain N (98%), straw P (40%), and grain P (44%) in comparison with the uninoculated control. In addition, application of the microbial consortium to maize (Zea mays L.) seeds led to considerable improvements in plant height (70%), cob length (67%), grain yield (69%), stomatal conductance (17%), water-use efficiency (96%), photosynthetic rate (22%), cob weight (1.63-fold), and transpiration rate (1.2-fold). Moreover, consortium inoculation resulted in a significant reduction in leaf Na+ (38%) content, as evidenced by reduced antioxidant activities (i.e., catalase [59%], superoxide dismutase [37%], glutathione reductase [45%], ascorbate peroxidase [19%], and malondialdehyde [53%]) after consortium application. In conclusion, the rhizobacterial consortium alleviated the negative impacts of salinity on maize growth by improving the soil enzyme activities and nutrient acquisition under salinity stress.