Morpho-Physiological Responses of Rice Towards Submergence Tolerance

Submergence has been a great abiotic stress in rice cultivation. In this study, fifteen rice genotypes and IR64-Sub1 as control were evaluated under submergence at vegetative stage, which imposed for 14 days after 20 days of germination. Morphophysiological traits such as change of chlorophyll content (CCC), elongation percentage (EP), coleoptile length (CL), survival rate (SR), photosynthesis rate (PR) and percentage of non-structural carbohydrate (NSC) were recorded before and after submergence imposition and analysed. The IR64-Sub1 showed the highest SR (88.89%) followed by UKMRC2 (67.22%) and UKM-2 (65.93%) while MR264 had the lowest SR (8.89%). In most cycles, SR was positively correlated with CL and PR but negatively correlated with EP and CCC. Only NSCC showed significant correlation with SR (p < 0.05), however the correlation was inconsistent across cycles. EP plays a major role in affecting SR under submergence. Genotypes with high EP consumed high amount of NSC, causing them unable to recover after submergence. The best three genotypes (IR64-Sub1, UKMRC2 and UKM-2) adopted the quiescence strategy to survive under submergence by limiting their growth as shown by the low EP. Genotyping using Sub1 closely linked markers found that no single genotype possess the Sub1 locus. This suggests the existence of gene/s or QTL/s other than Sub1 need to be discovered and survive under submergence of high yielding genotypes, UKMRC2 and UKM-2. UKMRC2 and UKM-2 can be recommended for submergence prone rice cultivating areas in Malaysia. (C) 2019 Friends Science Publishers