Analysis of Combining Ability of Sunflower (Helianthus annuus) Seed Yield under Normal and Water Stress Conditions

Production of high sunflower yield is important in sunflower breeding programs. With regards to the importance of estimation of general combining ability (GCA) and specific combining ability (SCA), genetic evaluation of sunflower seed yield was carried out in normal and water stress conditions using biplot analysis of 6×6 diallel design. Parental lines and their progenies were investigated using a randomized complete block design with three replications in each condition in greenhouse. According to the separate analysis of variance, mean squares of genotypes were significant for seed yield in 0.01 probability level in both conditions. The first two principal components explained 77.9% and 82.5% of the variation for seed yield in normal and stress conditions respectively. Therefore, it is possible to extract any information by using graphical method of biplot. Among studied parental lines, LR25 had the positive and the highest general combining ability in both states. RHA266 had positive and the highest specific combining ability in water stress condition and genotype LR4 had the negative and the highest specific combing ability in normal condition. Considering the polygon graphs of biplot, cross LR25 × LR4 in normal condition and crosses including LR25 × C104, LR55 × RHA266 and C100 × RHA266 in water stress condition, depicted high level of heterosis for sunflower yield. Results revealed that genotype C104 is suitable tester for recognition of general combining ability of studied genotypes.