The Gluten Composition of Wheat Varieties and Genotypes

C. W. Wrigley1, F. Bekes2, C. R. Cavanagh2, and W. Bushuk3

1 Food Science Australia and Wheat CRC, North Ryde (Sydney), NSW 1670, Australia 2 CSIRO Plant Industry, Canberra, ACT 2600, Australia 3 Food Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

*For any comments on or additions to these databases, please contact F. Bekes (ferenc.bekes@csiro.au) or C. Cavanagh (colin.cavanagh@csiro.au)

I. Gliadin 

II. HMW Subunits of Glutenin 

III. LMW Subunits of Glutenin 

BACKGROUND

The gluten proteins are unique in their ability to provide us with leavened bread and many other foods and industrial products. The composition of the component proteins of gluten, the gliadins and glutenin subunits, is known for a large number of wheat varieties and un-named genotypes. This information is spread throughout the literature and in private listings, but it is potentially valuable for many of the purposes, e.g., pursuit of population genetics, to determine how readily a specific combination of varieties could be distinguished on the basis of analyzing specific aspects of gluten composition, and to determine the value of specific genotypes as parent lines to achieve targeted genetic potential for dough quality.

It has thus been worthwhile to provide a compilation of gluten composition for the many genotypes for which gliadin and glutenin-subunit composition is known. This compilation was to have been included in an Appendix to the book published in 2006 by AACC International, under the title “Gliadin and Glutenin: The Unique Balance of Wheat Quality”, edited by C.W.Wrigley, F.Bekes and W.Bushuk. However, the list proved to be too large to include within the covers of a book; internet publishing proved to much more suitable. This is not the only website with information regarding wheat storage-protein alleles. At least two other websites contain similar or complementary information, part of the graingenes website compiled by Bob Graybosch (http://wheat.pw.usda.gov/ggpages/gopher/Quality/Molecular/HMW/) and the website of “Genes On-Line” (http://genbank.vurv.cz/wheat/pedigree/).

Refer to the book “Gliadin and Glutenin: The Unique Balance of Wheat Quality” for information about the chemistry, genetics and nomenclature for the three classes of proteins covered in the web site list, namely, the gliadins and the subunits of glutenin, both the high- and low-molecular-weight groups (HMW- and LMW-subunits, respectively). The information is provided in the form of alleles (shown as “a”, “b”, … etc.) appropriate to the locus (e.g., Gli-1, Glu-3) for each genome (A, B or D). In the case of the gliadins, there are two loci, for both Group 1 and Group 6 chromosomes. For the HMW subunits of glutenin, nomenclature is agreed for the subunits as well as for the alleles, so both forms are provided.

Biotypes and potential errors

There are potential difficulties in compiling such tabulations. For example, polymorphisms may exist for a specific variety; that is, different grains of the same sample differ in aspects of their gluten composition, but each aspect of composition may be authentic. Such “biotypes” may arise from the original cross that produced the variety under study, being sister lines with alternative alleles that have become fixed in the process of selecting the cultivar. In such cases, the tables indicate that alternative subunits have been detected, e.g., in the form “a/b”.

On the other hand, such variations may be due to contamination with foreign seed, thus providing wrong information. In such a case, the authenticity of the sample source should be examined. Examination of the composition of the parent lines (if definitely known) may help in establishing that the apparent polymorphism is not due to contamination, but rather that valid biotypes are present. Further problems include inconsistencies between published lists, differences in the methods used in obtaining composition data, and the significant difficulties in interpreting the results of protein fractionation, e.g., gel-electrophoresis patterns versus HPLC profiles.

I. Gliadin

II. HMW Subunits of Glutenin

III. LMW Subunits of Glutenin

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