SOME INTRA-VARIETAL NON-UNIFORMITIES IN Triticum aestivum CAN BE EXPLAINED AS REPEATED SPONTANEOUS MUTATIONS AT THE Gli LOCI

ABSTRACT 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 over-production of ω-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.