The genetics of β-amylase isozymes in wheat : 1. Allelic variation among hexaploid varieties and intrachromosomal gene locations.

Thirty-three β-amylase isozymes were separated in 'Chinese Spring' by IEF and the structural genes encoding seventeen of these were located by nullisomic analysis. The locations of the previously reported β-Amy-1 loci on chromosome arms 4Aβ (β-Amy-A1) and 4DL (β-Amy-D1) were confirmed and another set, β-Amy-2, was found on the group 5 chromosomes. A locus on 5AL (β-Amy-A1) was identified by nullisomic analysis and another on chromosome 5B (β-Amy-B2) was identified by analysis of inter-varietal chromosome substitution lines. The loci are complex, each coding for several isozymes, and allelic variation occurs at all four. Two alleles were identified at β-Amy-A1, five at β-Amy-D1, five at β-Amy-A2 and two at β-Amy-B2. Eleven different β-AMY phenotypes were distinguished amongst the 46 wheat varieties screened. The β-Amy-A2 locus was mapped by employing chromosome 5A recombinant lines and found to be closely linked and proximal to the awn inhibitor, B1, on the long arm. An attempt to map the β-Amy-D1 locus on chromosome 4D showed the gene to be located in the distal region of the long arm.