Relationship between grain yield and plant characteristics in grain sorghum genotypes under drought stress conditions

This experiment was conducted with 13 grain sorghum genotypes in three different moisture conditions including: non-stress and two water deficit conditions (in vegetative and reproductive stages) using randomized complete block design with three replications. In the non-stress experiment، irrigation applied according to the plant requirement، and for two experiments: (1) drought stress imposed in vegetative stage (since four leaves up to flowering stage) and (2) drought stress imposed in reproductive stage (since flowering up to maturity). Analysis of variance showed significant differences among genotypes in all traits in three conditions. Positive and significant correlations of grain yield with harvest index and grain. panicle-1 were obtained in non stress conditions. There were positive and significant correlation of grain yield with flag leaf height، plant height، harvest index and biological yield in drought stress in the vegetative stage as well as with harvest index and days to flowering in drought stress in the reproductive stage. Results of multiple linear regression analysis (MLRA) revealed that in non-stress conditions grain. panicle-1، flag leaf area، 1000 kernel weight، stem dry weight، plantheight، leaf dry weight and days to maturity، in drought stress in vegetative stage conditions، grain. panicle-1 and flag leaf height، and in drought stress in reproductive stage conditions، flag leaf area and panicle height were determined as independent variables that explained variations in grain yield as dependent variable in the models. Plant characteristics in non-stress conditions، vegetative and reproductive drought stress conditions explained grain yield variation with r= 0. 86، r= 0. 75 and r= 0. 56 coefficient of determination، respectively. Also path analysis for grain yield indicted that grain weight. panicle-1، grain. panicle-1 and stem dry weight hadthe highest direct effect in non-stress conditions، vegetative and reproductive drought stress conditions، respectively. These characteristics had the highest indirect effect through grain. panicle-1، grain weight. panicle-1، stem diameter، flag leaf area and plant height on increasing yield.