Combining ability analysis for yield and yield traits in Indian mustard (Brassica juncea L. Czern & Coss.)

Introduction

Among the oilseed crops cultivated in India, Brassica juncea holds a prominent position because of its economic value and wide adaptability. It is an important member of the rapeseed-mustard group and is extensively grown during the winter season in northern and north-western parts of the country. Globally, rapeseed-mustard ranks after soybean and palm oil crops in terms of edible oil production. Apart from household consumption, vegetable oils are increasingly used in biodiesel industries, thereby enhancing the commercial importance of oilseed crops throughout the world. The requirement of edible oils is increasing rapidly due to rising population and improved living standards. India depends heavily on edible oil imports to meet domestic demand. Indonesia and Malaysia are the principal exporters of palm oil, while Argentina plays a major role in soybean oil trade. Major biodiesel-producing countries include Brazil, Thailand, the European Union and Malaysia. During the Rabi season of 2024-25, rapeseedmustard in India produced more than 115 lakh tonnes from about 92 lakh hectares. Uttar Pradesh contributes nearly 10-15 percent of total national production. In the state, mustard cultivation is widely practiced under irrigated as well as rainfed conditions. Ballia district recorded productivity of nearly 1430 kg per hectare during 2024-25, indicating its importance in eastern Uttar Pradesh. Indian mustard seeds contain nearly 38-42 percent oil and the oil cake contains around 24 percent protein. The crop is also considered beneficial from nutritional and medicinal viewpoints because it provides vitamins, minerals and dietary fibre. Nevertheless, conventional mustard varieties contain undesirable substances such as glucosinolates and erucic acid, which reduce the nutritional quality of oil and meal and may lead to health disorders. Consequently, reduction of these antinutritional factors is one of the major aims of modern breeding programmes. Despite its importance, the average productivity of Indian mustard is still lower than its potential yield because of narrow genetic variability, susceptibility to diseases and pests and test weight (g), harvest index (%), oil content (%) and seed yield per plant (g). The mean data recorded for all characters were subjected to statistical analysis. Analysis of variance was carried out to test the significance of differences among treatments. Combining ability analysis was performed according to Griffing's (1956) method to estimate general combining ability (GCA), specific combining ability (SCA) and reciprocal effects. The statistical model used was: 𝑋 𝑖𝑗𝑘𝑙 = 𝜇 + 𝑔 𝑖 + 𝑔 𝑗 + 𝑠 𝑖𝑗 + 𝑟 𝑖𝑗 + 𝑒 𝑖𝑗𝑘𝑙 where, 𝑋 𝑖𝑗𝑘𝑙 represents the observation of the 𝑖 × 𝑗 𝑡ℎ genotype, 𝜇is the population mean, 𝑔 𝑖 and 𝑔 𝑗 denote general combining ability effects of parents, 𝑠 𝑖𝑗 represents specific combining ability effect, 𝑟 𝑖𝑗 indicates reciprocal effect and 𝑒 𝑖𝑗𝑘𝑙 denotes environmental error effect. Graphical analysis based on variance (𝑉 𝑟 ) and covariance (𝑊 𝑟 ) values was carried out according to the procedures suggested by Jinks and Hayman (1953) [3] , Jinks (1954, 1956) [4,5] and Hayman (1954, 1957, 1958) [6,7,8] . Components of variance due to additive and non-additive gene effects were estimated from mean squares. The ratio of GCA to SCA variances was used to determine the relative importance of additive and non-additive gene action for different characters. Economic heterosis and inbreeding depression were also estimated for yield and its contributing traits.

Results and Discussion

The present investigation conducted in Brassica juncea revealed significant variability among parents, F₁s and F₂ populations for all the traits studied, indicating ample scope for selection and hybrid improvement. Analysis of variance showed highly significant differences among genotypes, while non-significant replication effects confirmed the reliability of the experiment. The variation among hybrids indicated the involvement of both additive and non-additive gene action in the inheritance of yield and related traits. The estimates of GCA and SCA variances indicated predominance of additive gene effects for most characters, whereas traits like days to flowering, primary branches and test weight showed greater non-additive effects. Kranti and Urvashi were identified as good general combiners for earliness, while Maya, Aashirvaad and Azad-Mahak exhibited desirable GCA effects for seed yield per plant. Urvashi, Rohini and Varuna were superior for siliquae per plant and Aashirvaad, Basanti, Varuna and Kranti showed favourable GCA effects for oil content.

Conclusion

The present investigation in Brassica juncea revealed the presence of considerable genetic variability among parents, F₁s and F₂ populations for all the characters studied, indicating sufficient scope for selection and genetic improvement. Significant differences among genotypes confirmed the existence of wide diversity for yield and its contributing traits. The estimates of general combining ability (GCA) and specific combining ability (SCA) variances indicated the involvement of both additive and non-additive gene actions in the inheritance of different traits. Additive gene effects predominated for most characters, whereas non-additive gene action was more important for days to flowering, primary branches and test weight. These results suggested that simple selection methods may be effective for traits governed mainly by additive effects, while heterosis breeding could be more useful for traits controlled by dominance and epistatic interactions. Among the parents, Maya, Aashirvaad and Azad-Mahak were identified as superior general combiners for seed yield per plant, while Urvashi, Rohini and Varuna were found promising for siliquae per plant. Kranti and Urvashi proved useful for earliness and Aashirvaad, Basanti, Varuna and Kranti were desirable combiners for oil content. Among the hybrids, Maya × Azad-Mahak, Aashirvaad × Kranti, Azad-Mahak × Urvashi and Maya × Basanti exhibited high SCA effects for seed yield per plant and may be exploited for heterosis breeding. Crosses such as Aashirvaad × Kranti, Aashirvaad × Urvashi and Rohini × Varuna also showed superior performance for important yield contributing traits. Overall, the study indicated that both selection and heterosis breeding approaches can be effectively utilized for improvement of yield and related traits in Indian mustard. The superior parents and promising cross combinations identified in the present investigation may be used in future breeding programmes for development of high yielding, early maturing and better oil quality mustard varieties.

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