Tara Movaghar Hasani, Maryam Rezayian, Vahid Niknam, Javad Hamedi
Overall, seed bio-priming with both Streptomyces strains significantly enhanced the activity of the antioxidant enzyme superoxide dismutase (SOD) in both the shoots and roots of the two wheat cultivars under drought stress.
The use of bacteria to enhance drought tolerance in plants holds considerable promise for agricultural production. However, the effects of Streptomyces on plant drought tolerance remain poorly understood. In the present study, we investigated how wheat cultivars bio-priming with two desert-derived Streptomyces strains influences drought tolerance by examining both their physiological effects and the underlying mechanisms. Following seed bio-priming with two desert-derived Streptomyces strains (designated strains B3136 and B2482), we evaluated plant growth, lipid peroxidation, antioxidant capacity, and the accumulation of selected metabolites in two wheat cultivars (Sirvan and Moghan3) subjected to drought stress. Drought stress significantly enhanced shoot growth in Moghan3. In contrast, Sirvan exhibited a greater reduction in biomass under drought conditions than Moghan3. Bio-priming with strain B2482 significantly improved growth in Sirvan under 15% PEG-induced drought stress. A notable finding was the marked difference in proline accumulation between shoots and roots in both cultivars. Strain B3136 significantly increased proline accumulation and improved osmotic adjustment in both the shoots and roots of Sirvan under severe drought stress. Drought stress also increased H₂O₂ accumulation in the shoots of both cultivars, although this increase was more pronounced in Moghan3. Malondialdehyde (MDA) content was significantly higher in the shoots than in the roots of both cultivars. However, under moderate drought stress, the increase in root MDA content was substantially greater in Sirvan than in Moghan3. Bio-priming with both Streptomyces strains significantly reduced MDA accumulation in the roots of Sirvan under both moderate and severe drought stress. Interestingly, drought stress resulted in a reduction of MDA content in the roots of Moghan3, suggesting a more effective mechanism for limiting lipid peroxidation in this cultivar. Correlation analysis among the measured parameters indicated that flavonoids may contribute to reducing lipid peroxidation and mitigating oxidative damage in the roots of Moghan3. Based on the physiological and biochemical responses observed in this study, Moghan3 was characterized as drought-tolerant, whereas Sirvan was classified as drought-sensitive. Overall, seed bio-priming with both Streptomyces strains significantly enhanced the activity of the antioxidant enzyme superoxide dismutase (SOD) in both the shoots and roots of the two wheat cultivars under drought stress.