Genetic analysis of some agronomic traits in flax (Linum usitatissimum L.)

A complete diallel cross using eight flax genotypes including four Iranian breeding lines and four Canadian genotypes was carried out to estimate genetic parameters for days to flowering, days to maturity, plant height, primary branches per plant, number of capsules per plant, number of seeds per capsule, seed yield per plant, 1000-seed weight, seed yield and harvest index. Analysis of variances for the studied traits indicated highly significant differences among the genotypes. Significant general combining ability (GCA), specific combining ability (SCA) and reciprocal effects revealed meaningful contributions of additive, non-additive type of gene actions and maternal influence in governing the traits. The results showed that additive gene actions had greater effects on inheritance of days to flowering, days to maturity, plant height, primary branches per plant and 1000-seed weight. However, number of capsules per plant and number of seeds per capsule were largely controlled by dominance genetic effects, whereas both additive and non-additive gene actions were important in genetic control of harvest index, seed yield per plant and seed yield. The parental lines KH124, KO37, AH92 and SE65 exhibited positive and significant GCA effect on both seed yield per plant and seed yield. Parent KO37 also had the highest negative GCA for early flowering, early maturity and plant height. A considerable heterosis was also observed for the studied traits in some cross combinations and the highest heterobeltiosis values of 64.1, 35.2, 21.6, 77.2 and 91.3% were obtained for number of capsules per plant, number of seeds per capsule, 1000-seed weight, seed yield per plant and seed yield, respectively. These results imply the potential of producing superior cultivars through selection in segregating populations or heterosis breeding, providing that the technical problems hampering economical production of hybrid seeds in flax could be overcome.