Gene Action and Heterosis for Oil Yield and Component Characters in Sunflower*

The type of gene action has been studied for oil yield and component characters in two crosses of sunflower involving two selections from the variety ‘Peredovick’ and a dwarf selection from variety ‘Smena’. Simple scaling tests, joint scaling tests and interaction models employing six primary generations have been used to assess the occurrence and relative contribution of different components of epistasis. Epistasis has been found to occur for all the characters in both the crosses. The type of epistasis is compared with the occurrence of heterosis. It is found that complementary or duplicate type of epistasis is not as important in the expression of heterosis as are the relative signs and magnitude of additivt, dominance and interaction parameters. Keeping in view the fact that all types of gene action, i.e., additive, dominance and epistatic have been observed in the material, reciprocal recurrent selection is recommended as the suitable breeding methodology for genetic upgrading of this crop.