Analysis of genetic architecture for some physiological characters in sesame (Sesamum indicum L.)

Combining ability for some important physiological parameters in sesame were examined to understand the nature of gene action and to identify parents for breeding programme. Seven diverse genotypes of sesame, their 21 F(1)s and 21 F(2)s were grown in summer, 2003, in a randomized complete block design with three replications. Data were collected on leaf area index (LAI) at 30, 45, 60 and 75 days after sowing (DAS), crop growth rate (CGR) estimated between 30-45 DAS, 45-60 DAS and 60-75 DAS, days to peak flowering (DPF), duration of flowering (DF), duration from peak flowering to maturity (DFM), oil content in percentage (OC) and oil yield (OY) plant(-1). Analysis of combining ability was done on the above physiological characters following Method-2, Model-I of Griffing (Aust J Biol Sci 9:463-493 1956). Variances due to general combining ability (GCA) and specific combining ability (SCA) for all the physiological traits were highly significant in both F-1 and F-2 generations indicating importance of both additive and non-additive gene actions for the inheritance of all the physiological characters in both F-1 and F-2 generations. Preponderance of non-additive gene action was recorded for CGRs, LAI 3, LAI 4, DPF, DF and OY in both the F-1 and the F-2 generations. For OC additive gene action was predominant in F-1 while non-additive gene action in F-2. The genotype OS-Sel-2 appeared as best overall general combiner in both the F-1 and the F-2 generations. For DPF, DF and DFM, the variety B 67 was best general combiner, followed by CST 2002, which could be utilized for developing early flowering and early maturing lines with determinate growth habit. Association between GCA-effects and mean performance of the parents suggested that the performance per se could be a good indicator of its ability to transmit the desirable attributes to its progenies. Crosses CST 2002 x TKG 22, CST 2002 x MT 34, MT 34 x AAUDT 9304-14-4, AAUDT 9304-14-4 x B 67, TKG 22 x Rama and TKG 22 x B 67 which showed high SCA-effect for OY, also exhibited positive and significant SCA-effects for other physiological component characters in F-1 generation. The overall results indicated that crosses CST 2002 x TKG 22 and MT 34 x AAUDT 9304-14-4 could be utilized for development of high oil yielding hybrids. The crosses OS-Sel-2 x AAUDT 9304-14-4, AAUDT 9304-14-4 x B 67 and MT 34 x OS-Sel-2 could be promising for isolation of superior recombinants for high oil yield coupled with early maturity and other growth characters in advanced generations of segregation.