General (GCA) and specific (SCA) combining abilities in sunflower

Abstract

Used in this study were 20 new Rf-lines, five A-tester lines and their 100 hybrid combinations. A large number of agronomically important traits of these genotypes have been studied. The present paper reports the results for plant height, seed yield (kg/ha), seed oil content (%), oil yield (kg/ha), and resistance to Sclerotinia head rot. In most of the hybrid combinations significant heterosis of various intensity levels was found for all the above traits. Analysis of the combining abilities for the traits concerned has shown that there are significant differences among the Rf-lines and A-tester lines regarding the values of the general combining ability (GCA). In some of the lines highly significant positive and negative GCA effects were observed. Analysis of the components of genetic variance has shown both additive and nonadditive gene action to be responsible for the inheritance of the traits. Still, the contribution of the nonadditive component was more significant. This is supported by the GCA/SCA ratio values, which were lower than 1 and as such indicative of the higher importance of nonadditive genes in the expression of the traits. The largest contribution to the traits’ expression was that of the A-testers. The contributions of the Rf-lines and tester/line interactions were smaller. Based on the study’s results, it can be concluded that the following lines have the largest practical value in breeding terms: PR-ST-3A, Ha-26A, RHA-N-92, and RUS-RF-100.