Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 9/6/2005
Publication Date: 1/15/2006
Citation: Metakovsky, E.V., Branlard, G., Graybosch, R.A. 2006. Gliadins of common wheat: polymorphisms & genetics. Book Chapter. Pp. 35-84
Technical Abstract: Wheat gliadins are a highly polymorphic group of seed storage proteins arising from a series of complex genetic loci found on several chromosome arms. Gliadin encoding alleles are numerous, and their frequency differs amongst countries, with wheat cultivars from different countries being easily distinguished by electrophoretic analysis of gliadin proteins while cultivars from the same country often display much similar patterns. The uneven distribution of gliadin alleles in the cultivars discussed herein may result from selection during breeding programs or might have arisen as a consequence of “founder effects”, with similar patterns being due to reliance on a small number of ancestral cultivars in any given country. This chapter will discuss the genetic control, variation, origin and spread, and methodological aspects for the study of gliadin proteins of wheat grain. Gliadin (Gli) alleles were identified in 939 common wheat cultivars bred in 28 countries (http://www.aaccnet.org/); grain samples of these cultivars were obtained from different institutions from 14 countries. At least 18% of the cultivars were found to be heterogeneous and consist of two or more natural biotypes differing at their Gli loci. Various errors (admixtures, non-authenticity of grain samples, mistakes in pedigrees) were encountered. For example, 40 of 189 cultivars studied were found to be erroneous, either by pedigree or in grain samples tested. Analysis of Gli alleles was confirmed as a very precise method of wheat genotype identification. More than 1150 combinations of Gli alleles (gliadin genotypes) were found amongst the 939 cultivars studied. Allelic frequencies differed strongly in all the material and between countries. Country of origin specific genotypes was recognized and often traceable to landraces and ancestral cultivars of each nation. Winter and spring wheats were found to significantly differ in their Gli allelic compositions. Due to genetic linkage relationships, however, Gli alleles capable of always discriminating these market classes do not exist.