UC Davis

Linkages between high- and low-molecular-weight (M(r)) glutenin, gliadin and triticin loci in diploid, tetraploid and hexaploid wheats were studied by hybridization of restriction fragments with DNA clones and by SDS-PAGE. In tetraploid and hexaploid wheat, DNA fragments hybridizing with a low-M(r) glutenin clone were mapped at the XGlu-3 locus in the distal region of the maps of chromosome arms 1AS, 1BS, and 1DS. A second locus, designated XGlu-B2, was detected in the middle of the map of chromosome arm 1BS completely linked to the XGli-B3 gliadin locus. The restriction fragments mapped at this locus were shown to co-segregate with B subunits of low-M(r) glutenins in SDS-PAGE in tetraploid wheat, indicating that X Glu-B2 is an active low-M(r) glutenin locus. A new locus hybridizing with the low-M(r) clone was mapped on the long arm of chromosome 7A(m) in diploid wheat. No glutenin protein was found to co-segregate with this new locus. Triticin loci were mapped on chromosome arms 1AS, 1BS, and 1DS. A failure to detect triticin proteins co-segregating with DNA fragments mapped at XTri-B1 locus suggests that this locus is not active. No evidence was found for the existence of Gli-A4, and it is concluded that this locus is probably synonymous with Gli-A3. Recombination was observed within the multigene gliadin family mapped at XGli-A1 (1.2 cM). Although these closely linked loci may correspond to the previously named Gli-A1 and Gli-A5 loci, they were temporarily designated X Gli-A1.1 and X Gli-A1.2 until orthology with Gli-A1 and Gli-A5 is established.