THE ROLE OF SOIL MICROBES IN ALLEVIATING ABIOTIC STRESSES IN ECONOMICALLY IMPORTANT CROP PLANTS

Abstract

The present study aimed to investigate the role of Piriformospora indica, arbuscular myconrhizal fngi (AMF), and plant growth-promoting bacteria (PGPB) in alleviating drought and salinity stress in HD-2967 wheat and Maharaja BIO-9637 maize variety. In a completely randomized design experiment, wheat and maize plants were subjected to diferent water regimes viz. 75, 55, 45, and 35% field capacity (FC) and different levels of salinity viz. 0, 50, 100, and 200 mM NaCl under greenhouse conditions. Under different water regimes and salinity levels, microbial inoculation significantly enhanced the morphlogical, physiological, biochemical, and ultrastructural characteristics of the wheat and maize plants. Plants inoculated with PGPB, P. indica, and AMF showed increased shoot and root length, shoot and root biomass, leaf area, photosynthetic rate, transpiration rate, stomatal conductance, and internal CO, as compared to uninoculated plants under all water regimes and salinity levels. The PGPB, P. indica, and AMF inoculated wheat and maize plants accumulated higher content of glycine betaine, total sugars, trehalose, proline, putrescine, spermidine, carotenoids, proteins, a-tocopherol, and showed a decrease in lipid peroxidation, relative membrane permeability, and lipoxygenase enzyme (LOX) activity as compared to uninoculated plants. Besides, PGPB and P. indica wheat and maize plants showed a higher level of antioxidant enzymes viz., superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) than uninoculated plants under drought and salinity stress. However, AMF inoculation did not affect CAT activity in maize plants under drought and salinity stress, and wheat plants under salinity stress and its activity decreased with increasing levels of stress. Microbial inoculation helped wheat and maize plants to overcome water stres and salinity-induced deficiency of macronutrients (Ca", Mg", and K') and micronutrients (Cu, Mn, Fe, and Zn"), and reduced damage to the cell ultrastructure (plasma membrane and chloroplasts). Comparing the potential of microbial inoculants to increase growth, nutritional, biochemical, physiological, and ultrastructural changes, the PGPB-inoculated wheat and maize plants showed greater drought and salinity resilience followed by AMF and P. indica inoculated plants. These microbial inoculants offer a significant potential to meet the challenges of sustainable agriculture under drought and salinity conditions.