Electronic Journal of Plant Breeding, 5(4): 688-694 (Sep 2014) ISSN 0975-928X http://sites.google.com/site/ejplantbreeding 688 Research Article Combining ability and gene action studies for seed yield and its components in sesame (Sesamum indicum L.) Vavdiya, P. A.*, Dobariya, K. L. and Babariya, C. A. Main Oilseeds Research Station, Junagadh Agricultural University, Junagadh-362001 (Gujarat) Email:pareshvavdiya@gmail.com (Received: 10 June 2014; Accepted: 20 Nov 2014) Abstract A line x tester analysis using 12 lines and three testers was carried out to study the combining ability and gene action in sesame for seed yield and 14 quantitative traits. Analysis of variance for combining ability revealed significant differences among the mean squares due to lines, testers and lines x testers for all the characters except oil content, which indicated the existence of genetic diversity among the parents and hybrids. General and specific combining ability variances showed the involvement of both type of gene actions in the inheritance of these characters. Among the lines, IC-81564, NIC-75, Borda-1 and among testers, G.Til-10 were good general combiners for seed yield per plant and some of its contributing traits. The cross combination, IC-81564 x G.Til-10 showed significant and positive sca effect for seed yield per plant and involved good x good combining parents. It was followed by AT-238 x G.Til-10, NIC-75 x G.Til-4, TNAU-12 x G.Til-4, Keriya-2 x G.Til-3 and Keriya-2 x G.Til-10 which involved either good x good, good x poor or poor x poor combining parents. These crosses have been identified as best hybrids for improving seed yield per plant and could be evaluated under different environment to confirm their superiority. Key words Sesame, combining ability, gene action, line x tester analysis Introduction Sesame (Sesamum indicum L.) is one of the most ancient and important oilseed crop grown next to groundnut and mustard in India. The oilseed crops play important role in agriculture and industrial economy of our country. It is called as the ‘queen’ of oilseeds in view of its oil and protein which are of very high quality. In India, sesame is cultivated on an area of 19.01 lakh ha with production of 8.10 lakh tonnes and productivity 426 kg/ha (Anonymous 2011). However, the productivity is low in India as compared to other countries which need to be improved. In the absence of a viable male sterility system in sesame, hybrids have to be developed exclusively by hand emasculation and pollination as done in other crops like cotton. Commercial exploitation of heterosis is feasible only if the means of producing hybrid seeds economically viable. It is possible in sesame because indeterminate plant with epipetalous nature of the flower facilitating easy emasculation, low seed rate, high seed multiplication ratio, natural out crossing, frequent visit by a large number of insects including honey bees and higher number of seeds set in a single pollination. In an often cross- pollinated crop like sesame there is a good scope for exploitation of heterosis because out crossing reached up to 68% which indicates the potentiality of the crop for improvement in yields. Further, an understanding of the combining ability and gene action is a pre-requisite for any successful plant breeding programme. Testing the parents for their combining ability is very important because many times, the high yielding parents may not combine well to give good hybrids. Line x tester analysis helps in testing a large number of genotypes to assess the gene action and combining ability. The present experiment was, therefore planned to study combining ability and gene action in sesame. Material and methods The present study on sesame was conducted at Department of Genetics and Plant Breeding, Junagadh Agricultural University, Junagadh, Gujarat. Twelve diverse lines viz., IC-205314, IC- 43063, IC-81564, IC-204983, AT-164, AT-238, AT-115, Borda-1, Patan-64, TNAU-12, Keriya-2, NIC-75 and three testers viz., G.Til-3, G.Til-4 and G.Til-10. The selected 12 lines and three testers were crossed in a line x tester design during summer 2012 to produce 36 hybrids. The resulting 36 hybrids along with 15 parents were evaluated during kharif-2012 in a Randomized Block Design with three replications. Each plot was constructed with a row length of 3m and adopted a spacing of 45 x 15cm. All need based agronomic practices were followed during the crop growth period to raise a good crop. Observations were recorded on randomly selected five plants in each entry for 15 quantitative traits viz., days to 50 % flowering, days to maturity, plant height (cm), height to first