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Present investigation was carried out with 240 mutant lines developed from different combination of gamma rays and ethyl methyl sulfonate on three rice varieties i.e FR13A, FR13B and Labella along with three untreated checks (FR13A, FR13B and Labella). These were evaluated for their survival percentage under submerged condition and yield potential along with 9 other morpho-physiological traits using Type 2 modified augmented design during Kharif season of 2017 in the agroclimatic region of north bihar, India. Analysis of variance revealed highly significant differences among the mutant lines for all morpho-physiological characters under study. Higher magnitude of phenotypic coefficient of variation (PCV), genotypic coefficient of variation (GCV), heritability (broad sense) and genetic advance as percentage of mean were observed for number of tillers per plant, number of fertile tillers per plant, relative shoot elongation and survival percentage, indicating that these traits could be used as selection indices for yield improvement and submergence tolerance. Association study revealed that number of tillers per plant and survival percentage had significant positive high to moderate direct association with grain yield per plant under submergence condition. Thus, these traits may be used as selection criteria in further crop improvement programmes for submergence tolerance.