Combining ability and gene action for agronomic traits and oil content in sunflower (Helianthus annuus L.) using F1 hybrids

General and specific combining abilities as well as genetic variance components for different agronomic traits in sunflower (Helianthus annuus L.) inbred lines were estimated using “Line × Tester” analysis method. Six new restorer lines were crossed with four CMS lines as tester in 2006 growing season. The 24 F1 single cross combinations were planted in complete randomized block design with four replications in Khoy Field Research Station in 2007 growing season. There were significant differences between hybrids for all traits except for head diameter. Variances among CMS lines for all traits were greater than restorer lines indicating the possible existence of some degrees of maternal effect on some traits, particularly, seed and oil yields. Variances of “Lines × Tester” were not greater than variances for either CMS lines or testers for any traits. This implies the importance of additive effect on concerned traits. Life-cycle duration, 1000 seed weight, seed number head-1 and oil yield were under control of both additive and dominant effects. Seed yield was mainly governed by dominant effects. However, plant height and oil content were controlled by additive effects. Over dominant effects for life-cycle duration and seed yield and complete dominant for plant height were also observed. Principle component analysis (PCA) revealed close positive relationship between seed yield, oil yield and seed number head-1, whereas there were negative association between these traits and 1000 seed weight. Restorer line “R21” and CMS line “CMS356” had stronger effect on their corresponding hybrids. “R23 x CMS78” was identified as superior early maturity hybrid with high oil content and yield.