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Analysis of components of heterosis over better parent revealed that both digenic and trigenic epistatic interactions had an important role to cause significant and positive heterosis in the cross HI 8062 x JNK-4W- 128. Additive x additive x dominance (x) followed by additive x additive (i) and additive (d) frequently contributed to the expression of significant heterosis in this cross under both the environments (Table 3). Earlier Maloo (1978) and Verma (1981) also observed significant heterosis for this trait. Absence of heterosis in remaining two crosses could be attributed to internal cancellation of the components of heterosis. Significant inbreeding depression was also observed in the second and third cross (late sown) due to the dissipation of non-additive dominance effects or epistatic effects involving dominance in F2 generation.

The results of the present study revealed that as a consequence of higher magnitude of digenic and trigenic interactions, non-fixable effects were higher than the fixable effects. Naturally, the successful breeding methods will be the ones, which can mop-up the genes to form superior gene constellations interacting in a favorable manner. The breeding methods suggested to achieve this objective are restricted to recurrent selection (Joshi 1979) and diallel selective mating (Jensen 1978). Furthermore, sowing environments should also be taken in consideration before finalizing the breeding method for its improvement. Favorable environment must be considered for taking advantage of its simple inheritance to achieve desirable improvement to get high grain yield in durum wheat in future.

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