COMBINING ABILITY ANALYSIS IN DIALLEL CROSSES OF WHEAT (TRITICUM AESTIVUM L.)

Wheat is a predominant cereal crop of the world and constitutes important source of carbohydrate and protein. It is considered as king of cereals as it provides foods to 36% of the global population contributing 20% of the food calories. At global level, India rank second largest wheat producing nation with 13.43% global wheat production after China which contributes 17.7% to the world wheat production (USDA 2012). Hybridization is the most potent technique for breaking yield barriers and evolving varieties having a built in high yield potential. The understanding of various characters and identification of superior parents are important pre-requisite for launching effective and efficient breeding programme. Selection of parents on the basis of phenotypic performance alone is not a sound procedure since phenotypically superior lines may yield poor recombination. It is therefore, essential that parents should be chosen on the basis of their genetic value. Combining ability analysis provide information on additive and non-additive variances (i.e. dominance and epistasis), which are important to decide the proper parents for hybridization to produce superior hybrids. The performance of parent may not necessarily reveal it to be a good or poor combiner. Therefore, gathering information on nature of gene effects and their expression in terms of combining ability is necessary. At the same time, it also elucidates the nature of gene action involved in the inheritance of characters. The information regarding general combining ability (gca) effects of the parents is of prime importance because it helps in successful prediction of genetic potentiality which would give desirable individuals in subsequent segregating populations. However, specific combining ability is associated with interaction effects which may be due to dominance and epistatic components of variation that are non-fixable in nature thus it would be worthful for commercial exploitation as hybrids. General combining ability effects often are larger than specific combining ability effects, but enough exceptions exist to make further use of hybrids worthwhile. Thus, gene action and combining ability relation to heterosis lies in determining whether heterosis is fixable or predictable. Busch et al. (1974), Bailey and Comstock (1976) and Cox and Murphy (1990) claimed that in some cases, possibility of developing predominant genotype is greater if both parents have similar performance instead of one parent being inferior or superior in terms of one or more traits. The performance of parent may not necessarily reveal it to be a good or poor combiner. Therefore, gathering information on nature of gene effects and their expression in terms of combining ability is necessary. At the same time, it also elucidates the nature of gene action involved in the inheritance of characters. General combining ability (GCA) is attributed to additive gene effects and additive x additive epistasis and is theoretically fixable. On the other hand, specific combining ability attributable to non-additive gene action may be due to dominance or epistasis or both and is non-fixable. The parents which are genetically superior and diverse in the traits of interest are utilized for varietal development programme. The choice of parental material used in the hybridization scheme does contribute significantly for the development of a suitable genotype. In systemic breeding programme, selection of parents with desirable characterisABSTRACT In order to realize the combining ability of wheat, 15 hybrids were synthesised in a 6 x 6 diallel fashion excluding reciprocals and to isolate the good combiner for various yield component traits. Results on gene action and combining ability indicated that both additive and non-additive gene effects are importance in governing the expression of these yield component traits. Single seed descent method can be applied to exploit additive gene effects whereas non-additive gene effects could be valuable in hybrid wheat breeding programs. Three parents viz.; K-8962, Kalyansona and Sonalika were identified as most promising parents due to having good general combining ability for grain yield and some of the other important traits. Among the crosses significant and desirable sca effects in order of merit for yield and yield contributing traits were exhibited by HUW 510 x PBW 373, HUW 510 x HUW 234, Sonalika x K-8962,Sonalika x HUW 234 and Kalyansona x K-8962. Therefore, these crosses could be utilized for further selection of high yielding progenies to achieve a quantum jump in improvement of wheat crop.