Genetic analysis of head inclination and its components in selected sunflower hybrids

To provide information about genetic control of head inclination in sunflower, 12 selected hybrids developed by crossing four lines and three testers were evaluated as a line × tester mating design using randomized complete block design with three replications in Karaj, Iran. The results showed that the parental lines contributed, more than other sources, in variation of head weight (62.4%) of hybrids while contribution of the testers was more for head diameter (62.8%), plant height (48.6%), head height (70.5%), achene yield (41.7%) and head inclination (54.5%). We found that the two hybrids; RGK33 × AGK370 (23.7%) and RGK33 × AGK356 (24.0%) had the lowest head inclination, respectively, while among the parental lines only RGK33 and AGK356 were in suitable range (25-35%) indicating that crossing the parental lines with undesirable head inclination may lead to the production of hybrids with suitable head inclination. We also found that head weight and head inclination are controlled mainly by additive gene action that suggests the crucial role of parental lines in development of hybrids with desirable head inclination. Both additive and non-additive gene action were significant for head diameter, plant height, head height and achene yield. Over-dominant gene action observed for plant height, achene yield and inclined length, and partial dominance for head diameter, weight, height and inclination. Higher broad sense heritability for plant height (0.86), head weight (0.72), head height (0.73) and head diameter (0.71), and lower heritability for head inclination, indicated that heritability of head inclination is independent from these components. All hybrids developed by crossing of restorer lines RGK21 and RGK33 had suitable head inclination as compared with the progenies of RGK15. This information is valuable for improvement of head inclination and developing ideo-types in sunflower breeding programs.