Relationships of Heterosis and Specific Combining Ability with Genetic Distance among Lines of Sunflower and Their Single Crosses for Grain Yield of Plant


This investigation was carried out in a farm at Al-hawija, west of Kirkuk Governorate and that the pure lines of sun flower EMB, EUR, L3, L6, L10 and PERE12, and all possible single, three-way and double crosses among them were planted using randomized complete block design with three replications, and based on the means of characters: height, number of leaves per plant, stem diameter, leaf area, head area, number of seeds per head, fertility percent, 100 seeds weight, grains yield per plant and the percent of oil and protein, the cluster analysis was performed to put the lines (parents of single crosses), lines and single hybrids (parents of three-way hybrids) and single crosses (parents double cross hybrids) separately in groups and estimation of the genetic distance between any of them, in order to determine the relationship of genetic distance with means performance, heterosis (based on the mid parents, better parent and the commercial variety Eur flower) and the specific combining ability for grains yield per plant in the case of each of the three types of hybrids. The results showed in the case of single hybrids that correlation coefficients between genetic distance values and all of the values of the means performance, heterosis and the specific combining ability were all positive, but it did not reach the significance limits. In the case of three-way hybrids triple genetic distance was non significantly negatively correlated with means performance, heterosis based on commercial variety and special ability, while significantly positively correlated with heterosis based on mid or better parents, and in the case of double cross hybrids, the genetic distance was positively and significantly correlated with the values of heterosis based on mid or better parents, non significantly positively correlated with means performance and heterosis based on commercial variety and correlated weakly with specific combining ability values. It is concluded in the case of the three types of hybrids access to genetic distance in prediction of heterosis based on mid or better parents because their relationship was more pronounced.