Effect of moisture stress on physiological characteristics and antioxidant system in rice (Oryza sativa L.) seedlings of a recombinant inbred line (RIL) population

Moisture stress is a major constraint affecting plant growth and development. Seeds of a recombinant inbred line (RIL) population of rice (Oryza sativa L.) were raised under laboratory conditions at 35°C, 16h light and 8h dark. Germination, Seedling establishment, physiological and biochemical traits associated with moisture stress tolerance were studied. Twenty RILs, their parents (PR-120 and UPLRi7) and four checks (IR-64, APO, CT-6510 and BM-370) were tested for moisture stress tolerance at two stress levels of -0.4Mpa and -0.6Mpa respectively induced by polyethylene glycol (PEG-6000). Seedling vigour index and stress tolerance index decreased to varying degree with an increase in stress levels. Among the biochemical parameters, total soluble sugars, proline, tocopherols and ascorbic acid (ASC) content and activities of antioxidant enzymes viz. superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were significantly increased in all the genotypes under moisture stress. At higher level of moisture stress (−0.6Mpa) a positive correlation was observed between proline, seedling vigour index and tocopherol content. Tocopherol content was in turn positively correlated to total soluble sugars and activities of superoxide dismutase (SOD) enzyme. All these are known to contribute to stress tolerance.