Diallel Analysis of Yield and It’s related Traits in Sunflower (Helianthus annuus L.) under Well-watered and Water-stressed Conditions

Drought stress is one of the factors which influence sunflower production. Hence, breeding for tolerance to drought stress has become a major focus. In this paper, combining ability, gene action and genetic analysis of several characteristics were studied for five sunflower inbred lines and their ten hybrids (fifteen genotypes). The materials were evaluated in two separate experiments using a Randomized Complete Block Design (RCBD) with three replications in well-watered and waterstressed states and in field condition. Data were analyzed by Griffing’s diallel analysis model 1 (fixed effects) and method 2 (parents and crosses). Combined analysis of experiments revealed significant differences among genotypes for all studied traits. Combining ability analysis revealed that in well-watered conditions, general and specific combining abilities (GCA and SCA) effects were significant for all studied traits except for the leaf number. In water-stressed condition, GCA and SCA effects were significant for all studied traits except for the head and stem diameter. The Griffing diallel analysis showed that the genotype LR4 could be considered as the best combiner with the highest GCA effect for seed yield per plant, number of filled seed, stem diameter and head diameter in the sunflower breeding programs. In both water treatment conditions the cross ‘RHA266xLR4’ showed the highest positive SCA effects and the highest mean value for seed yield per plant.