Evaluation of some Agronomic Traits and their Association with Grain Yield in Mutant Rice Lines under Normal and Post-anthesis Drought Stress Conditions

In order to evaluate the effect of drought stress and determine of effective traits on grain yield and estimate of genetic parameters, 18 mutant rice lines were studied in normal and drought stress conditions. The experiments were carried out separately using randomized complete block design with three replications during cropping season 2014-2015 at Iranian Rice Research Centers in North of Iran, Rasht. High values of heritability, genetic advances and genetic variances were observed for plant height, tiller number, filled grain number and unfilled grain number in both conditions, but grain productivity and grain yield were appeared only under drought stress conditions. This indicated the additive effects of genes in controlling of these traits and, therefore, these traits can be improved by selection in breeding programes. There were positive correlations between grain yield and tiller number, panicle exsertion, grain productivity and width and length of flagh leaf in normal irrigation condition. Grain yield had also positive correlation with flagh leaf width, panicle exsertion, filled grain number, grain productivity and width and length of grain under drought stress conditions. Regression and path analyses indicated positive effects of grain width, grain productivity, flagh leaf width, filled grain number, tiller number and internode length in normal irrigation conditions and grain productivity, grain width and tiller number under drought stress conditions. Therefore, it is possible to improve grain yield using these variables. The genotypes including G1, G2, G3 and G4 had the highest values of grain yield (2788, 2163, 2178 and 2194 kg ha -1 ) under drought stress conditions, and influencing traits on grain yield. Due to the stress index (SI), these genotypes were also as drought tolerant and, thus, can be used for introducing the drought tolerance cultivar.