Genetic diversity between diverse height categories of bread wheat

Sixty four F₁’s and F₂ of wheat from a 8 × 8 diallel and 55 F₂’s from a 10 × 10 diallel (where eight parents were common) were subjected to D²-analysis to measure the genetic diversity and components of genetic variation involving different height group parents and their F₂, populations.

Tall, d₁, d₂, d₃ and d₄ semidwarf parents were distinctly delineated along with their respective hybrids and reciprocals barring a few exceptions. However, d₁ and d₂ semidwarf parents and hybrids showed minimum genetic divergence. Considerable divergence was present both within and between height groups. Culm length and 100-grain weight were the major components of divergence at both intra and inter-cluster levels. The nature of gene action for plant height, 100-grain weight, spikelets per ear and rust incidence was predominantly additive and were partially dominant in the F₁. Genes for increased plant height, more ears per plant, higher 100-grain weight and yield per plant were mostly dominant. It seems possible that seed size and spikelets per ar among semidwarfs may be improved upto certain extent (due to higher additive genetic variance, increased proportion of non-additive component to additive component, presence of only three or more genes or groups of genes for dominant gene for these characters).