Genetic control of growth habit and awnedness in common wheat was studied by the aneuploid and the conventional methods of analysis. Using the 21 monosomic lines of the spring variety, Chinese Spring, as female parents, crosses were made with seven varieties. In addition, diallel crosses were made among the seven varieties and Chinese Spring.
Growth habit was found to be controlled by genes belonging to three allelic series Sg₁, Sg₂ and Sg₃, located on chromosomes XVIII, IX and XIII, respectively. The Sg₁ and Sg₂ series appeared to have three alleles and the Sg₃ series had two alleles; the alleles being Sg₁, Sg₁^c and sg₁, Sg₂, Sg₂^c and sg₂ and Sg₃ and sg₃ in order of dominance for each series.
Genotypes of the eight varieties are proposed, namely, sg₁ sg₂ Sg₃ for Elgin, Kharkov and Jones Fife, Sg₁^c Sg₂^c Sg₃ for Chinese Spring, Sg₁^c Sg₂ Sg₃ for Red Egyptian, Sg₁ Sg₂^c Sg₃ for S-615 and Sg₁ Sg₂ sg₃ for Prelude and Red Bobs.
All winter varieties studied carried the typical winter habit genes, sg₁ and sg₂. The gene sg₁ was much more effective than sg₂ in delaying heading. Spring varieties carried some of the less effective spring habit genes, Sg₁^c, Sg₂^c or sg₃ instead of the typical spring habit genes, Sg₁, Sg₂ or Sg₃.
Concerning awnedess, monosomic analysis revealed that awnlessness of Chinese Spring is ascribed to two inhibitors Hd and B₂ on chromosomes VIII and X, respectively while that of Red Bobs to the presence of inhibitors B₁ on chromosome IX and B₂ and the absence of the a₁ promotor on chromosome II; awnlettedness of Elgin and Jones Fife is controlled by the B₁ gene; and awnedness of Prelude, Kharkov, S-615 and Red Egyptian is due to absence of all inhibitors. Conventional analysis confirmed the results obtained by monosomic analysis and indicated that an inhibitor on chromosome XVI of Chinese Spring affected F₂ segregation of awnedness when crosses were made between Chinese Spring and other varieties.