Comparative Analysis of High‐Molecular‐Weight Glutenin Subunit Composition in Various Triticum Species

Variation in high‐molecular‐weight glutenin subunit composition amongst Triticum durum cvs. of different origins was investigated by SDS‐PAGE and compared with that reported for T. dicoccum and T. aestivum. Tetraploid wheat collections (408 cvs.) were found to carry nearly twice as many Glu‐A1 and Glu‐B1 alleles as a hexaploid wheat sample of comparable size. In each of the taxa considered, allelic variation at the Glu‐B1 locus was markedly greater than that observed for Glu‐A1. However, because all the Glu‐B1 subunits so far discovered exhibit a restricted and distinctive mobility range during. SDS‐PAGE, it is suggested that they are derived from a single source, possibly from Aegilops searsii. Most durum cvs. carried a ‘null’Glu‐A1 allele and therefore fewer subunits than dicoccums and common wheats. It is argued that differences in the frequency of occurrence of ‘null’Glu‐1 alleles between taxa probably resulted from random samplings made by early agriculturalists and breeders, rather than from an inherent tendency of polyploid wheats to suppress the activity of “redundant” genes.