Acclimatization of non-cultivated rice landraces to early moisture stress mediated by enzymatic antioxidants and osmolyte accumulation

Moisture stress affects the physiological and biochemical characteristics of plants such as the propensity for cellular water, induces stomatal closure, and reduces photosynthetic capacity, ni-trate assimilation and substantial anabolic metabolism. In this study we assessed the antioxida-tive enzymes and osmolyte accumulation of fifty traditional non-cultivated rice landraces from Tamil Nadu, India. Artificial moisture stress was imposed in a hydroponic setup with maximum osmotic potential of (-) 15 bars. On the basis of drought and leaf rolling scores at 26 d, thirteen landraces were carried forward for further studies. The root/shoot ratio (R/S) was also significant for the selected landraces against IR64 as drought-susceptible check. The genotypes Kuliyadichan, Chandaikar, Mallikar, Nootripathu and Rajalakshmi were able to withstand in-tense moisture stress at 26 d with a score of 0 and 1, according to standard evaluation system for rice. Photosynthetic pigment and proline content of the above landraces increased during mois-ture stress in accordance with the positive check IR 64 (Drt1), however differential responses ob-served in all the landraces. Enzymatic antioxidant markers such as superoxide dismutase, cata-lase and peroxidase in shoots of all the selected landraces were greater than IR 64 (Drt1), under moisture stress. We identified Kuliyadichan, Rajalakshmi and Nootripathu as promising lan-draces with substantial moisture stress tolerance. Further, a positive correlation between overall seedling development and antioxidant enzymes as well as proline accumulation was observed un-der moisture stress. The mechanisms governing drought tolerance/avoidance in these moisture stress tolerant rice landraces might be attributed to active antioxidant defense system and proline accumulation for alleviating induced oxidative stress. Thus, the identified non-cultivated tradi-tional rice landraces may be employed as potential donors for rice improvement programme to-wards climate resilience.