Combining Ability for Yield and Agronomic Characters in Sunflower.

This research was conducted to estimate general and specific combining abilities for yield, oil content and agronomic characters of sunflower inbred lines. Seven sunflower inbred lines were crossed in 7×7 half diallel to obtain 21 F₁ hybrids. The 7 inbred lines and 21 hybrids were arranged in a randomized complete block design with three replications at two locations (SUT Farm and National Corn and Sorghum Research Center, Nakhon Ratchasima, Thailand) during 2008-2009. General combining ability (GCA) and specific combining ability (SCA) effects were estimated on yield, head diameter, 1,000-seed weight, plant height  and oil content. The results revealed that GCA mean squares were highly significant for head diameter and significant for yield and oil content. Mean squares for SCA were highly significant for plant height and 1,000-seed weight, while those of yield, head diameter and oil content were non-significant. Components of variance showed that the GCA variance was higher than the SCA variance for yield, head diameter and oil content. These results indicated that additive gene action was more important than non-additive gene action for these traits. Inbred line 5A exhibited the highest GCA effects for yield and oil content, followed by the line 2A. Among the crosses, 2A×5A showed the greatest positive SCA effects for 1,000-seed weight and oil content. Thus, the two inbred lines (2A and 5A) revealed good potential to be used as parents for hybrid.

 Key words: sunflower, diallel cross, GCA, SCA