Monosomic Analysis in Bread Wheat II. Identification of Chromosomes Carrying Genes for Awning and Glume Beak

Inheritance of awning and the shape of glume beak was studied in crosses of three varieties of wheat, E. 952 (Rio Negro), E. 220 (Kenya C 10854) and N.P. 790, with 21 different monosomic lines of Chinese Spring.

E. 952 has the recessive alleles of genes Hd and B₂, the two awn inhibiting genes present on chromosomes VIII and X of Chinese Spring. E. 220 lacks the genes Hd and B₂ on chromosomes VIII and X respectively but has the dominant awn inhibitor B₁ on chromosome IX. N.P. 790 has the recessive allele hd on chromosome VIII, Bi on chromosome IX and a gene b₂^a for half awned condition, allelic to B₂ on chromosome X. The presence of this allele, though inferred by Watkins and Ellerton (1940), has not so far been clearly demonstrated. Acuminate glume beak is associated with full beardedness and occurs only in the recessive condition of the awn inhibiting genes B₁ and B₂. B₂ individually reduces beak length and determines acute shape. B₁ also reduces glume beak and determines obtuse shape. It is epistatic over B₂. Chinese Spring has acute beak due to the presence of B₂ gene on chromosome X. E. 952 has acuminate beak being a full bearded variety with recessive alleles of awn inhibitors. Both E. 220 and N.P. 790 have obtuse beak due to the presence of gene B₁ on chromosome IX.