Physiological and antioxidant responses associated with gene introgressed rice ( L.) lines under complete submergence.

Rice is the only crop which is well adapted to aquatic environment but, it is unable to survive if completely submerged for several weeks. Breeding rice varieties with submergence tolerance is one of the best approaches to alleviate the adverse effect of submergence which requires the introgression of gene into elite rice varieties. Hence, the study was undertaken to introgress submergence tolerant gene into the rice variety Jaya through Marker-Assisted Backcross Breeding. Also the physiological and biochemical responses like survival percentage, underwater shoot elongation, total carbohydrate content and superoxide dismutase activity were also studied in introgressed lines. We could develop twenty introgressed lines with region of 3.1-5.1mb and with 80.0- 95.3% recurrent parent genome recovery. introgressed Jaya lines and the tolerant checks FR13A and Swarna had lower shoot elongation under water, higher superoxide dismutase activity (about 5 times) upto 4 h after de-submergence which resulted in higher survival percentage. The reduced shoot elongation of tolerant varieties reduced the utilization of stored carbohydrate. Through our research we introgressed gene into rice variety Jaya through Marker-Assisted Backcross Breeding and could study the physiological responses under submergence by which we confirmed the presence of gene in these lines. These lines could be field evaluated and could be released as a new variety thus helping the farmers of flood prone areas of Kerala.