Some intra-varietal non-uniformities in Triticum aestivum can be explained as repeated spontaneous mutations at the Gli loci

Intra-varietal non-uniformity, presumably caused by spontaneous mutations at the Gli loci, was detected by means of seed-by-seed electrophoretic analysis (APAGE) of wheat storage protein, gliadin, in two independent sets of grain samples of Triticum aestivum world-wide cultivars registered during the 20th century (in total, 12,035 seeds studied). The frequency of null alleles, which caused a loss of all gliadin electrophoretic bands encoded by one Gli locus, was found to be strongly disproportional among six Gli loci; thus, the Gli-B1null occurred 20 times more often than the Gli-B2null. The presence of the null mutation at a Gli locus was frequently accompanied by the over-production (visible as a remarkable increase of staining intensity of some APAGE bands) of gliadins encoded by other Gli loci. Nulls at the Gli-B1 locus were, as a rule, accompanied by the overproduction of omega-gliadins encoded by the Gli-D1. At the Gli-B1 locus, mutants were discovered that lacked more than one gliadin, but not all gliadins composing a block. The loss of one APAGE band, as well as an alteration of the electrophoretic mobility (EM) of one band in the electrophoregram of a given cultivar, was also observed. Alteration of the EM of one APAGE band occurred mainly among gliadins encoded at the Gli-2 loci, particularly at the Gli-B2. A frequency (obviously under-estimated in our work) of occurrence of about 1% was observed for seeds carrying any presumed spontaneous mutations at Gli loci.

Automated summary

Intra-varietal non-uniformity in wheat cultivars was observed due to spontaneous mutations at the Gli loci, leading to null alleles causing loss of gliadin electrophoretic bands. The null mutants were disproportional among different Gli loci, with some resulting in over-production of gliadins encoded by other loci. Additionally, mutations at Gli loci were found to result in loss of specific gliadins, alteration of electrophoretic mobility, and under-estimated occurrence rate of about 1%.