Salt-resistant Streptomyces consortia promote growth of rice (Oryza sativa var. Swarna) alleviating salinity and drought stress tolerance by enhancing photosynthesis, antioxidant function, and proline content

Abstract

Salinity and drought are the major abiotic stresses that significantly affect growth and productivity, necessitating the development and exploration of technologies to enhance tolerance of the crop plants. This study explored the role of four plant growth-promoting Streptomyces, i.e. Streptomyces chilikensis RC1830 (assigned as A), Streptomyces griseoincarnatus RB7AG (assigned as D), Streptomyces barkulensis RC1831 (assigned as B), and Streptomyces chitinovorans RC1832 (assigned as C) in mitigating stresses and improving rice plant growth (var. Swarna). Rice plants were inoculated with different Streptomyces consortia and exposed to 40 mM NaCl for salinity stress and 55 % FC (Field capacity) for drought stress. The study found that stresses adversely affected physiological parameters and triggered the production of antioxidant enzymes like superoxide dismutase, catalase, and peroxidase. However, inoculation of consortia at a concentration of 108 CFU/mL not only promoted the growth of the plants but also mitigated the negative effects of salinity and drought compared to non-inoculated controls. Among the treatments, ABCD consortia (RC1830, RC1831, RC1832, RB7AG) demonstrated the most significant improvements followed by ABD (RC1830, RC1831, RB7AG), boosting shoot length, root length, total chlorophyll, and proline content. This also enhanced superoxide dismutase, peroxidase, and catalase activities under stress conditions. Overall, Streptomyces inoculation improved stress tolerance in rice plants by enhancing photosynthetic capacity, antioxidant defense mechanisms, and proline content. These PGPS inoculants present a promising ecological approach to mitigate the impacts of abiotic stress on crops.

Keywords

• Plant growth promotion
• Antioxidant enzymes
• Plant stress
• Microbial consortia