Self-fertility (SF) is an essential trait that contributes to yield stability in sunflower (Helianthus annuus L.), particularly in the absence of pollinating insects. We used a full-diallel design with 12 sunflower parents, including confectionary and nonconfectionary types, to assess (i) combining ability for SF, (ii) the relationship between SF and other traits, and (iii) microsatellite markers for tracking self-incompatible S alleles. Twelve parents and their 132 Fs were evaluated for SF in two environments. Self-fertility was correlated with final seed length (r = -0.57, P < 0.01), suggesting that SF was possibly influenced by floret characteristics. A genetic analysis of SF showed that both general combining ability (GCA) and specific combining ability (SCA) were significant, although after seed length was used as a covariate, the contribution of SCA effects increased to 65% of the variance and narrow-sense heritability was almost zero. The SCA effects were in part explained by the interaction of various combinations of S alleles. These results suggest that for programs targeting high-SF confectionary sunflower it would be difficult to predict the SF of hybrids based on the performance of their parents; therefore, F hybrid evaluation would be necessary. Our study suggested that factors controlling SF included GCA/SCA effects, S alleles, and floret characteristics. It also demonstrated the value of combining molecular and quantitative genetics for elucidating the inheritance of a complex trait.
