Mitigating drought stress in wheat: growth promotion and physiological adaptations induced by root endophytic bacteria isolated from hot and cold arid desert agroecosystems of India.

Drought stress reduces wheat productivity, and forecasts indicate significant declines in cereal yields. This study investigated root-endophytic bacteria from Indian hot and cold arid deserts to enhance drought tolerance in wheat plants. Of the 196 isolates, 60 endorhizospheric bacteria, mainly Pseudomonas, Exiguobacterium, and Sphingobacterium species, showed superior desiccation tolerance and plant growth-promoting (PGP) traits compared to non-rhizospheric isolates. The top 20 isolates enhanced wheat seed germination and seedling vigor, particularly in a drought-tolerant cultivar. Testing of five promising isolates (Pseudomonas rhodesiae BT3, Sphingobacterium faecium BT22, Advenella kashmirensis BL7, Exiguobacterium undae WL15, and Pseudomonas gessardii WL73) under different water potentials revealed their adaptive PGP strategies. P. rhodesiae BT3 produced high levels of indole-3-acetic acid (IAA), promoted proline accumulation, and supported nitrogen fixation. E. undae WL15 excelled in exopolysaccharide production and maintained phosphate solubilization under severe stress. Inoculation of drought-stressed wheat with these isolates improved the plant performance metrics. E. undae WL15 and P. rhodesiae BT3 increased shoot length, relative water content, and membrane stability in the seedlings. These bacteria enhanced antioxidant enzyme activity, increased proline and total soluble sugar levels, and reduced lipid peroxidation in plants. This study highlights the potential of endophytes such as P. rhodesiae BT3 and E. undae WL15 as bio-inoculants to enhance wheat productivity in water-scarce environments.