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A perusal of the general combining ability (gca) estimates over the environments showed that parents HD 2285, HD 2329 and Raj 1972 were good general combiner for grain yield per plant in both the generations under all the three planting dates (Table 4). The parent Durgapura 65 also emerged as good general combiner for grain yield per plant. Results further indicated that parents HD 2285, Raj 3077, Lok-1 and Raj 1972 were the best general combiners to breed for higher protein content (Table 4). The general combining ability analysis estimates of yield contributing traits over environments further depicted that WH 157 emerged as good general combiner for flag leaf area, tillers per plant, spike length, grain yield per spike and grains per spike. Similarly parent HD 2329 and HD 2285 were suitable for earliness, plant height, flag leaf area, grain yield per spike, 1000-grain weight and harvest index, and HD 2285 and Raj 3077 were also good combiner for grains per spike. Sonalika was observed good general combiner for 1000-grain weight and earliness. Apparently, therefore, it is still further scope for improving upon the combining ability for component traits as none of the combiners for grain yield was a high combiner or at least an average combiner for all the desirable traits. It seems feasible that the gca rank for grain yield is related to the gca for the useful yield components. It is therefore, recommended that the breeder should breed for superior combining ability for the components traits with an ultimate objective to improve the over all gca for grain yield in wheat. The parents HD 2285, HD 2329 and Raj 1972 could be utilized intensively in hybridization program to accelerate the pace of genetic improvement of grain yield in bread wheat. The parents HD 2285, Raj 3077, Lok-1 and Raj 1972 exhibited highly significant positive gca effects in all the environments both in F1 and F2 generations and hence, they were to be considered to breed for higher protein content. The parents HD 2285 and Raj 1972 can be intensively used in the hybridization program aimed at amelioration of grain yield and protein content through development of new plant type in bread wheat.

In order to synthesize a dynamic population with most of the favorable genes accumulated, it will be pertinent to make use of the aforesaid parents, which are good general combiner for several characters, in a multiple crossing program. Apart from conventional breeding methods resting slowly upon additive or additive x additive type of gene action, population improvement appears to be a hopeful alternative. Diallel selective mating system (Jensen 1970) sounds to be a good technique, which delays quick fixation of gene complexes, permits breakdown of linkage, general fostering of recombinations and concentration of favorable genes/gene complexes, into central gene pool, by a series of multiple crosses.

Normally the sca effects do not contribute tangibly in the improvement of self-fertilizing crops, except where commercial exploitation of heterosis is feasible. Breeder's interest, therefore, vests in obtaining transgressive segregants through crosses and producing more potent homozygous lines. Jinks and Jones (1958) emphasized that the superiority of the hybrids might not indicate their ability to yield transgressive segregants, rather sca would provide satisfactory criteria.

The analysis of specific combining ability effects revealed that in the present investigation none of the hybrids showed consistency for their high sca effect for all the characters in different environments. The desirable crosses (on the basis of per se performance, high sca effects and heterosis) for grain yield per plant were Sonalika x WH 157, Lok-1 x Durgapura 65, Sonalika x HD 2285, CPAN 3004 x Raj 1972, HD 2428 x WH 157, HD 2329 x WH 157, HD 2428 x Durgapura 65, CPAN 3004 x HD 2329 and Durgapura 65 x Sonalika for either one or two environments. These crosses were also found superior for one or more yield contributing characters ie CPAN 3004 x Durgapura 65 for spike length and HD 2428 x Sonalika for tiller per plant and 1000-grain weight; Sonalika x HD 2285 for grains per spike; Lok-1 x Durgapura 65 for harvest index, spike length and grains per spike; HD 2329 x WH 157 for tiller per plant and grains per spike and HD 2428 x WH 157, for flag leaf area. The best crosses for protein content were Durgapura 65 x HD 2329, CPAN 3004 x WH 157, HD 2428 x HD 2329, Raj 1972 x WH 157, HD 2428 x Raj 1972 and HD 2329 x HD 2285. This information of the above desirable crosses may be used in making an appropriate choice of the parents in a crossing program involving multiple parents for tangible advancement of grain yield in bread wheat.

In the present study, comparison of sca effects of these top crosses and gca effects of their parents indicated that such crosses in general involved one parent with good gca effect and the other with-poor or average gca effects. Hence, the presence of at least one good general combiner appeared to be desirable for getting the better hybrids. The sca effects of the crosses under different environments were also considered for tangible advancement of various characters as well.

The sca effects for all the characters were in accordance with per se performance indicated by highly positive correlation between hybrid performance and sca effects calculated from both the generations (Table 5). However, the relative ranking of the best crosses on the basis of sca effects and per se performance exhibited slight differences. Thus, crosses which would give the highest sca effects would not necessarily give the highest mean values as later the realized value was good for all the characters, studied. Invariably the crosses showing high sca effects for grain yield revealed that higher sca effects would be observed for at least one or more of its component characters.

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