Electronic Journal of Plant Breeding, 8(1): 51-58 (March 2017) ISSN 0975-928X http://ejplantbreeding.com 51 DOI: 10.5958/0975-928X.2017.00007.2 Research Article Studies on combining ability and heterosis using cytoplasmic male sterility system in Indian mustard [Brassica juncea (L.) Czern & Coss.] Ashutosh Kumar*, Raghvendra Tiwari, Praveen Pandey and K. Kumar Department of Genetics and Plant Breeding, Narendra Deva University of Agriculture and Technology, Kumarganj, Faizabad-224229 (U.P.) India. E-mail: ashutoshpnd07@gmail.com (Received: 16 April 2015; Revised: 03 Feb 2017; Accepted: 12 Feb 2017) Abstract A field experiment on Indian mustard consisting thirty two parents (two lines + thirty testers) and their sixty crosses was conducted to estimate general and specific combining ability of parents and crosses, respectively. The variances due to SCA were higher than GCA variances for almost all traits, confirming the presence of non-additive gene action in the inheritance of these characters. Among testers, NDRE-22, EJ-22, RH-919, Divya-22, NDRE-08-04, NPJ-135, PRE-2009-09, NPJ-148 and PRE-2007-06 were found good general combiners for seed yield. The crosses, CMSMori x NPJ-135 (13.17 %) and CMSNDRE-4 x PRE-2007-06 (12.83 %) showed significant sca effect and heterosis over standard varieties Kranti and Maya, respectively. Key words Combining ability, Indian mustard, seed yield and CMS Introduction The prime objective in Indian mustard breeding is to achieve high production and productivity. This can be achieved by successful exploitation of hybrid vigour, which would depend upon the identification of hybrids that are more productive than either of the parents and standard check cultivars. For the purpose, the availability of suitable and stable male sterility, fertility restorer system may be best tools for achieving the goal. At present, cytoplasmic male sterility system (CMS) has been discovered in B. juncea (Rawat and Anand, 1979; Pradhan et. al., 1991) and raised hope that hybrids in Brassica would soon be reality with stable performance. Combining ability analysis is useful technique for understanding the relative magnitude of GCA and SCA variances. The high yield in F 1 may be due to fixable (additive and additive x additive epitasis) or non- fixable (non-additive) type of gene actions. The selection of parents having high genetic potential is crucial as analyzing and handling of very large number of crosses resulting from numerous parents would be an unrealistic and perhaps impossible task. More than 20 % heterosis has been recorded in Indian mustard with respect to seed yield and its attribute traits has been reported with hybrids showing greater advantage under adverse environmental conditions (Banga and Labana, 1984 and Dhillon et al., 1990). Hence, the present investigation was envisaged to study the general and specific combining ability effects. Materials and methods The experimental materials comprised of two lines, 30 testers and their 60 crosses were evaluated in a randomized block design with three replications at Research Farm of Genetics and Plant Breeding of N.D. University of Agriculture and Technology, Kumarganj, Faizabad (U.P.) during Rabi 2011-12. Each entry was accommodated in a single row of 5 meter length with row to row and plant to plant distances of 30 cm and 15 cm, respectively. All the recommended package of practices were followed throughout the crop growth to establish successful crop stand. The data were recorded on five randomly selected plants leaving border plants in each replication for days to 50 per cent flowering, days to maturity, plant height (cm), number of primary branches per plant, number of secondary branches per plant, length of main raceme (cm), number of siliquae on main raceme, number of seeds per siliqua, 1000-seed weight (g), biological yield (g), harvest Index (%), oil content (%) and seed yield per plant (g). The oil content was estimated by NIR on dry seed basis. The data were subjected to „line x tester‟ analysis for combining ability (Kempthorne, 1957) and standard heterosis (Fonseca and Patterson, 1968). Results and discussion The analysis of variance revealed highly significant differences among parents as well as crosses for all the characters except number of primary branches per plant. Variances due to parents vs crosses were also highly significant for all the characters except biological yield. Variances due to lines x testers were significant for days to 50 per cent flowering, days to maturity, plant height, biological yield, oil content, number of primary branches per plant and number of secondary branches per plant. The variances due to lines revealed significant differences for days to 50 per cent flowering, number of siliquae on main raceme, biological yield and length of main raceme. The variances due to testers also revealed significant differences for all the character except