Electronic Journal of Plant Breeding, 8(1): 226-235 (March 2017) ISSN 0975-928X http://ejplantbreeding.com 226 DOI: 10.5958/0975-928X.2017.00032.1 Research Article Combining ability and gene action study for grain yield and its attributing traits in Indian mustard V.R. Akabari, N. Sasidharan and Vipul Kapadiya Department of Genetics and Plant Breeding, Anand Agricultural University, Anand – 388 110 (Gujarat), India. E-mail: virenbreeder@gmail.com (Received: 10 April 2016; Revised: 31 Jan 2017; Accepted: 08 Feb 2017) Abstract Combining ability and nature of gene interaction that contribute to seed yield and its attributing traits in Indian mustard were investigated using 60 hybrids developed by crossing three females (lines) with twenty males (testers) in a Line x Tester mating system. The results revealed that GCA and SCA ratio (σ 2 GCA/σ 2 SCA) was less than unity for all the traits except for days to 50 % flowering. This indicated that non-additive components played relatively greater role in the inheritance of all the traits except days to 50 % flowering for which greater role of additive components was found. The estimate of GCA effects indicated that the parents GM-2, NRCM-120, PAB-9511 and IC-261670 were identified as good general combiners indicating their ability in transmitting additive genes in the desirable direction to their progenies. The hybrids viz., GM-2 x PYM-7 (10.81), GM-3 x NUDH-45-1 (10.70) and GM-3 x PAB-9511 (8.36) were found to be the best specific crosses for seed yield per plant. Among these hybrids, GM-2 x PTM-7 was also recorded significant sca effects in desired direction for number of primary branches per plant, number of secondary branches per plant and number of siliquae per plant, while GM-3 x NUDH-45-1 also exhibited significant sca effects for number of primary branches per plant, number of secondary branches per plant, number of siliquae per plant, siliquae length and oil content. Therefore, these hybrids can be further exploited for selection of transgressive segregants. Key words General combining ability (GCA), seed yield, specific combining ability (SCA), Indian mustard, yield components Introduction Indian mustard is an important rabi season oilseed crop in India and occupies a premier position among the oilseed crops. It is popularly known as rai, raya or laha in India. Among the major oilseed producing countries India contributes about 7% at the global level. India, with an area of 7.20 million hectares, 7.88 million metric tonnes production and 1094 kg/ha productivity, ranks second in area and third in production in rapeseed-mustard scenario of the world in 2014-2015 (Anonymous, 2015). To fulfill requirement of ever-increasing population of India, there is a dire need of improving genotypes for better seed yield potential per unit area basis. This could be achieved by exploring the maximum genetic potential from the available germplasm of Indian mustard. Breeders should concentrate on development of productive mustard varieties by crossing good general combining lines for seed yield and selecting transgressive segregants from the resulting hybrids. The success of any breeding programme largely depends upon the choice of parents and the breeding procedure adopted. Combining ability analysis was carried out in the present investigation to obtain useful information for selection of better parents and crosses for their future use in breeding program. In addition to this, information regarding nature and magnitude of gene action could also be obtained, which is useful in deciding breeding methodology aiming to exploit fixable (additive) and non-fixable (non- additive) genetic variances. Materials and methods The experimental material comprised of three females, twenty male parents (Table 1) and their 60 F 1 S developed by crossing three females (lines) with twenty males (testers) in a Line x Tester mating system. The seeds of 60 F 1 hybrids and 23 parents were produced by hand emasculation-hand pollination and selfing, respectively during rabi 2013-14. These 60 F 1 hybrids along with 23 parents were evaluated in randomized block design with three replications during rabi 2014-15 at Anand Agricultural University, Anand. This site located at 220 35’ North Latitude and 720 55’ East longitude at an elevation of 45.1 m above mean sea level. Inter and intra row spacing was kept 40 and 15 cm, respectively. All the recommended package of practices was adopted to raise a good crop. For recording observations, 5 competitive plants were randomly selected and tagged from each treatment in each replication and the mean value per plant was computed for various yield and its attributing traits viz., plant height (cm), number of primary branches, number of secondary branches, effective length of main branch (cm), number of siliquae on main spike, number of siliquae per plant, siliqua length (cm), number of seeds per siliqua, seed yield per plant (g), thousand seed weight (g), oil content (%) and protein content (%). The phenological characters viz., days to flowering and days to maturity were recorded on