A half diallel set of six parents was used in this study to estimate general and specific combining ability along with heterosis in some important traits of flax. The six parents and their 15 single crosses were evaluated in 2013/ 2014 winter season in a randomized complete block design with four replications. General and specific combining ability were evaluated according to Griffing (1956), method 2 and Model I. Results indicated that genotypes along with crosses mean squares were significant for all studied traits. Parent P1 was among the highest mean values for most studied traits. The single cross P1 x P2 gave the highest significant mean values for stem diameter, number of fruiting branches/ plant, number of seeds/ capsule, seeds yield/ plant, and oil %. The cross P1 x P3 expressed the most desirable mean values for days to flowering and straw yield/ plant. General and specific combining ability were significant for all studied traits and the GCA/ SCA ratio revealed the predominance of additive and additive x additive gene action in controlling most traits. Parent P1 seemed to be the best general combiner for flowering date, stem diameter, total length, number of fruiting branches, No. of capsules/ plant, number of seeds/ capsule, seed yield/ plant and straw yield/ plant. The most desirable SCA effects were detected for the crosses P1 x P2 for stem diameter, No. of seeds/ capsule, seed yield/ plant and oil %, the cross P1 x P5 for straw yield/ plant.
The cross P1 x P2 gave the most desirable heterotic effects for stem diameter, seed yield/ plant and oil% relative to mid parent and better parent heterosis. The best heterotic values for straw yield/ plant were obtained for the cross P1 x P5 (mid parent) and P1 x P3 (better parent).
Key words: Flax, Diallel analysis, combining ability, flax
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