Determination of the best selection indices in mutant lines of rice at different moisture conditions

To determine the best selection indices for facilitating the selection procedure in a reproductive stage of 96 mutant lines (M2) of rice under different moisture conditions, an experiment was carried out in two environments at the research farm of Gonbad Kavous University in 2016 base on randomized complete block design with three replications. Evaluating the reduction percentage in the average values of traits showed that the most damages as affected by drought stress was due to decreases in numbers of filled grains, numbers of tillers, and 1000-grain weight. Results of stepwise regression analysis indicated that, 1000-grain weight, plant height, numbers of filled grains, numbers of days to flowering, flag leaf rolling, numbers of tillers, and panicle length traits were respectively entered into the final multivariate regression model as important traits affecting grain yield under a flooded condition, and 1000-grain weight, numbers of days to flowering, plant height, fertility percentage, panicle length, flag leaf frying, and numbers of tillers were respectively entered under drought stress. Evaluation of direct and indirect effects of studied traits on the grain yield using a path analysis showed that, 1000-grain weight, due to a positive and high direct effect, and numbers of filled grains, due to an indirect effect via 1000-grain weight, can be considered as the most important traits for increasing the grain yield under flooded condition. However, 1000-grain weight and fertility percentage can be introduced as appropriate selection criteria for the grain yield under a drought condition.