Heterosis and combining ability analysis for oil yield and its components in rapeseed

The occurrence of heterosis for oil percent, oil yield and some yield components has been studied in 36 F-1 combinations derived from nine parental genotypes (from France, Denmark, Sweden, Germany and Iran) of rapeseed according to a diallel design. In the 2008 and 2009 seasons the F-1 hybrids and the parental genotypes were sown according to simple lattice design. In both years, the mean squares due to general combining ability (GCA) and specific combining ability (SCA) were also highly significant. SCA genetic variances were greater than GCA and more important for the traits, showing the predominance of non-additive gene action. The results of combined analysis over year indicated SCA x year interactions were significant sources of variation in the inheritance of all traits while GCA x year interactions were significant only for number of seeds per pod of plant and oil percent. Significant positive heterotic effects including mid-parent and high parent heterosis were observed for all the triats studied but for different number of crosses. Parental genotypes with best GCA (Opera and Talaye) and its utilization as one of the parents produced excellent hybrid combinations having valuable SCA determination for oil yield. F-1 hybrids like Orient x Zarfam, Orient x Talaye, Opera x Talaye performed well in GCA and SCA determination and heterosis. This outcome could be a good indicator to identify the most promising genotypes to be utilized either as F-1 hybrids or as a resource population for further selection in rapeseed improvement.