Role of Ascorbate and Ascorbate-Glutathione Cycle for Photosynthetic Protection in Selected Indigenous Rice Landraces Under Drought Stress

From precise drought tolerance screening of local rice landraces of Koraput, six rice landraces were identified as superior drought tolerant capacity in our earlier study. However, little information is available on their physiological response of redox regulation and photochemical activity under drought stress. The present work evaluates their redox regulations driven by ascorbate-glutathione cycle and photochemical activity of photosystem II under simulated drought stress by polyethylene glycol 6000. Leaf chlorophyll content, electron transport rate and effective quantum yield of PSII were significantly higher in studied indigenous rice genotypes in comparison with susceptible check variety under drought condition. Further, greater quantities of ascorbate and elevated levels of ascorbate-glutathione cycle enzyme activities were observed under drought treatment in studied indigenous rice genotypes in compared with susceptible IR64. The findings suggested that maintenance of better photochemical activity in studied rice genotypes under water-deficit condition may be due to improved redox regulation of ascorbate and efficient ascorbate regeneration pathways. This study thus shows a new light into drought stress response of indigenous rice of Koraput with global implications.