NSIC Rc222-derived Mutants Characterized for Field Performance Identifying Putative Complete Submergence Tolerant Lines

In the 2019 dry season (DS) 18 genotypes – comprised of 13 mutant lines derived from seed mutation of NSIC Rc222, four check varieties, and one wildtype – were evaluated for field performance under submergence stress (STR) and non-stress irrigated (NSTR) condition in comparison to checks and wildtype to determine the effect of submergence to agronomic traits, grain yield, and yield components. Submergence was imposed at 21 d after transplanting (DAT) and lasted for 8 d. Survival of the mutant lines was comparable to the tolerant check FR13A, IR64-Sub1, and PSB Rc68, as well as to the wildtype NSIC Rc222. Variance component analysis showed that variation observed among the genotypes for all traits evaluated was due to the growing condition. Significant effect of submergence stress on agronomic traits, grain yield, and yield components was observed, with seven mutant lines yielding significantly higher than the checks and wildtype under stress. Promising stress-tolerant mutant lines – with comparable performance under NSTR and superior performance under STR to the checks and wildtype – were identified, viz. Sub 100, 101, 104, 105, and 110. These mutant lines can serve as possible donors of genes for tolerance to submergence stress or can be developed directly as varieties for registration and release for commercial cultivation.