Physiological Mechanism and Nutrient Management Strategies for Flood Tolerance in Rice Grown in Lowland Flood Prone Ecosystem

In flood-prone areas, rice must have flood tolerance characteristics either through genotypic selections or by nutrient application management strategies. The current study was conducted at ICAR Research Complex for Eastern Region, Patna during the wet season to investigate the effect of post-flood nutrient application methods on submerged rice survival and productivity. Our study showed that the 3-d submergence duration had no effect on the survival (100%) of 21-day-old seedlings but survival percentage decreased to 97 and 65% at 7-d and 11-d submergence, respectively. Total chlorophyll, total soluble sugar, and starch concentrations also exhibited a similar pattern of decline. The activity of anti-oxidative defense enzymes (CAT, POX, SOD, and APX), recorded just after de-submergence was found to be 1.5-10-foldhigher than before submergence, increasing with the increase in the severity of stress. Additional post-flood application of K2O and N at 5-6 days after de-submergence led to the improvement in photosynthetic rate, yield attributes, and grain yield. An additional 10 kg each of N and K2O produced maximum 1000-grain weight and higher grain yield and harvest index. After submergence, the meta-analysis exhibited a significant reduction in total chlorophyll concentration due to increasing submergence duration, whereas the significantly higher activity of antioxidants was recorded irrespective of submergence duration. In association with the better anti-oxidative defense mechanism of Sub1 varieties, the additional doses of N and K2O at 5-d after de-submergence significantly enhanced the survival, post-flood recovery, and the rate of photosynthesis after de-submergence. These nutrient management options can provide an opportunity to explore the productivity potential of the SUB1-introgressed variety under natural flash-flood conditions, helping to cope with the existing problems in flood-prone areas. The findings of the study suggest that a proper time and method of N application with basal P can significantly contribute to higher rice yield in flash-flood prone areas.