Genetics of Semidwarfism in Common Bread Wheat

The genic behaviour of semidwarf clum length was studied among a number of divergent F₁ and F₂ diallel crosses, involving tall d₁, d₂, d₃ or d₄ (single, double, triple, quadruple semidwarfs respectively) height group parents of common spring bread wheat. The conclusions were drawn from means, variances, dominance values, number of effective factors, and F₂ frequency curves. The alleles for tallness were partially dominant over alleles of short culm length in tall × d₃ or d₄ crosses. However, tallness was nearly or completely dominant over d₁ or d₂ and so was d₁ over d₂. Whereas, d₁ or d₂ were partially dominant over d₃. Operation of one gene in d₁ and d₂ height groups and two genes in d₃ and d₄ height groups, with unequal effects in ‘Norrn 10’ derivatives and with equal effects in Olesen’s derivatives, was indicated along with some minor modifiers. Use of single, double, triple or quadruple semidwarf terms for classifying different height categories has been suggested in modification of one-gene, two-gene, and three-gene semi-dwarfs.