Genetic analysis of quantitative and quality traits under varying environmental conditions in bread wheat
S.K. Joshi, S.N. Sharma*, D.L. Singhania and R.S. Sain
Department of Plant Breeding and Genetics, Rajasthan Agriculture University, Agricultural Research Station, Durgapura, Jaipur 302 018, Rajasthan, India
Summary
Genetic analysis was undertaken in 10 x 10 half parental diallel progenies (F1 and F2) for quantitative and quality traits under varying environmental conditions in bread wheat (Triticum aestivum L). Genotype x environment interaction was found significant for all the characters in both F1 and F2 generations, indicating existence of non- linear response of genotypes to the varying environments. Both additive and non-additive gene effects were present in the material under study. However, the ratio of additive/non- additive genetic variance revealed that there was preponderance of additive gene effect in the expression of yield per plant, protein content and other yielding contributing traits studied. Both the gene effects were highly influenced by the environments. The parents WH 157, HD 2329 and HD 2285 were the best general combiners for grain yield and also high to average general combiners for most of the important traits. The parents HD 2285, Raj 3077, Lok-1 and Raj 1972 were the best general combiners to breed for higher protein content. The best specific cross for grain yield and protein content was Sonalika x WH 157 and Durgapura 65 x HD 2329, respectively. Biparental mating and/or diallel selective mating systems under favorable environment are suggested for a more tangible advancement in bread wheat.
Key words: bread wheat, combining ability, gene action, quantitative traits
Introduction
Wheat today occupies a unique position among cereals in India and attained a record 75.75 million tones of wheat production and continued to remain as the second largest producer of wheat in world. This achievement will go a long way in boosting the confidence of India in food security and to establish itself as a competitor in the global market. With all these achievements, the issue ahead are even more challenging. By the year 2020 India's population will be 1.3 to 1.4 billion and we visualize that to make available 180 g of wheat per person per day, the country should produce 109 million tones of wheat by 2020 (Nagarajan 2001). In India wheat grain is used by human beings mainly in the form of chapatti hence wheat cultivars with high baking quality will be preferred. The gliadin protein (a constituent of gluten) probably accounts for much of the baking differences observed among cultivars. Hence, there is need to develop high yielding wheat varieties with high protein.
An efficient breeding program is needed to break down the present plateau of productivity of wheat varieties. Grain yield, the major concerned of most crop breeders, is a complex character and is the result of interaction of many direct and indirect component traits, influenced by environmental fluctuations. As such it is difficult to manipulate yield through recording yield alone. Several workers have suggested use of component characters as selection criteria for yield improvement. However, the compensatory effects and negative correlations between these traits may nullify improvement based on individual components. The experimental evidences clearly indicated that major yield components in wheat are tillers per plant, grains per spike and 1000-grain weight (Sharma and Kaul 1986; Maloo et al. 1993). Improving these direct and some other indirect components, grain yield can be improved. For this, combining ability studies are frequently used by plant breeders to evaluate newly developed genotypes for their parental usefulness and to assess the gene action involved in various characters, so as to design an efficient plan for further genetic upgrading of the existing material. However, the combining ability studies in a single environment may not provide precise information as environmental effects play an important role and greatly influence the combining ability estimates (Singh et al. 1986; Menon and Sharma 1994). Such information on combining ability analysis of wheat under varying environmental conditions is scanty. It is, therefore, necessary to assess combining ability, components of variance and combining ability x environment interaction for grain yield and its components to ensure better production and gain under selection. Present study deals with such endeavors.