Variation of harvest index in several wheat crosses

Summary Harvest index was studied in F₁ and F₂ generations of eight wheat (Triticum aestivum L.) crosses and their reciprocals. The parental varieties involved in the crosses represented a fairly wide range of character expression for plant height, tillering potential, grain yield per plant and harvest index. Differences between reciprocal crosses were not evident for the expression of harvest index of the crosses under study. Means and degrees of dominance of F₁ and F₂ populations suggested partial dominance of high harvest index over low harvest index. The pattern of variation among F₂ segregates was quantitative and the distribution was normal. The gene action governing the expression of harvest index was largely additive. Evidence was obtained for non-additive gene action in some crosses. There was complete absence of high parent heterosis for harvest index in the F₁'s but midparent heterosis was found to be present in all crosses. Estimates of heritability and genetic advance were moderate to high. Usefulness of selecting for harvest index as a measure of yield efficiency particularly in early generations is discussed.