Diallel analysis of metric traits in sesame (Sesamum indicum L.)
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Sesame in Kenya is mainly produced by peasant farmers. Production has mainly been limited by poor soils, erratic rainfall amounts, pest and disease attack, poor agronomic practices and use of unimproved cultivars. This study was thus conducted to determine the nature of gene action for yield, yield components and other traits and the association of componental characters with yield. Nine sesame (Sesamum indicum L.) cultivars and their 36 F1 progeny were evaluated for yield per plant, capsules per axil, branches per plant, days to 50% flowering, height to first branch, 1000-seed weight, seeds per capsule, capsule length, capsules per plant, height ~t maturity, height to first capsule and locules per capsule in a diallel cross at the University of Nairobi Dryland Field Station, Kibwezi in 1993. The experimental design was a randomised complete block design with three replications. General and specific combining abilities were determined by Griffing's (1956) method 2, Modell. Additive gene effects were more significant for days to 50% flowering, height to first capsule and 1000-seed weight. Non-additive gene effects were more conspicuous for seeds per capsule, capsule length, capsules per plant and height to first branch. SPS SIK 50/1 was the best general combiner for yield per plant, 1000-seed weight and capsule length. The crosses SPS SIK 114 x SPS SIK 111, SIK 131 x SPS SIK 111, SIK 131 x SPS SIK 114, SIK 131 x SPS SIK 6 and SPS SIK 50/1 x SPS SIK Z2 were the most promising, with high specific combining ability for yield per plant, capsules per plant, seeds per capsule, capsule length and 1000-seed weight. Yield heterosis of the F1 over the better-parent ranged from -48.45% to 115.02%. Crosses involving SIK 131 showed negative better-parent heterosis for capsules per- axil while the rest of the crosses showed no heterosis. Crosses involving SPS SIK 6 showed negative better-parent heterosis for locules per capsule while the rest showed no heterosis. All crosses except SPS SIK 6 x SPS SIK 111 showed a reduction in height to first branch. The parental cultivars SIK 131 and SPS SIK 004/1 were found to impart earliness to their progeny. Capsule length, 1000-seed weight, seeds per capsule and capsules per plant were positively and significantly correlated with yield per plant. From the path coefficient analysis seeds per capsule, 1000-seed weight and capsules per plant exerted the greatest direct influence on yield.