The effect of drought stress on genetic parameters of yield and some morphophysiological traits of sunflower (Helianthus annuus L.)

To study the effect of drought stress on genetic parameters of yield and some morphophysiological traits of sunflower, the hybrids obtained from the cross of eight restorer lines with three sterile male lines and two normal irrigation and drought stress conditions were evaluated in a split-plot experiment based on randomized complete block design with three replications. The results of line × tester analysis showed that under normal conditions, line and tester effects were significant for all studied traits. Under stress conditions, the effect of lines was significant in chlorophyll index, initial growth rate, and plant height and the effects of tester were significant in early growth rate, plant height, stem diameter, and grain yield. Estimation of the effects of general combining ability of traits showed that two lines, C122, C123, and A19 tester had the highest positive combining ability in grain yield and could be used as good parents for producing suitable hybrids in breeding programs. Estimation of heterosis of the studied traits showed that the highest rate of heterosis of grain yield under normal and stress conditions were 126.6% and 123.9%, respectively, for the A112×C41 hybrid. Two traits stem diameter, and head diameter showed a significant correlation with grain yield under normal conditions, while four traits, initial growth rate, plant height, stem diameter, and head diameter, was correlated positively with grain yield under stress conditions.