368 Allelic variation at Glu-D1 loci for HMW glutenin subunits – Quantification by multistacking SDS-PAGE of wheat grown under nitrogen fertilization.

J. ZHU (1), K. Khan (1), S. Huang (2), and L. O’Brien (3). (1) Department of Cereal Science, North Dakota State University, Fargo, ND 58105; (2) Bread Research Institute of Australia, P.O. Box 7, North Ryde, NSW 2113, Australia; (3) Plant Breeding Institute, University of Sydney, Narrabri, NSW 2390, Australia.

Two biotypes of an Australian wheat cultivar Warigal, differing only in the Glu-D1 HMW glutenin subunits 5 + 10 and 2 + 12, were used in this study. The wheats were grown with two treatments of nitrogen applications at 0 and 200 kg/ha rates to produce samples with low and high protein contents. Unreduced proteins containing the SDS-soluble glutenins and the other protein classes were analyzed by multistacking SDS-PAGE that separates the glutenin into six distinct different size aggregates. The results indicated that the SDS-soluble glutenins not only significantly increased in proportion in total SDS-soluble proteins but also increased in size distribution as protein content increased with nitrogen application. The SDS-insoluble glutenins had a greater ratio of HMW to LMW subunits indicating that they were larger polymers than the SDS-soluble glutenins. The ratio of x to y subunits was greater in the SDS-insoluble glutenins, due to a higher increase of x- than y-type subunits, especially the 1Dx subunit, than in the SDS- soluble glutenins. The biotype with HMW subunits 5 + 10 had a larger size distribution of the SDS-soluble glutenins and larger sizes of the SDS-insoluble glutenin polymers than the 2 +12 type. The 5 + 10 subunits were associated with a greater effect on Chinese steamed breadmaking quality than the 2 + 12 subunits. The ratio of HMW to LMW subunits and the ratio of x to y subunits may be used to predict the sizes of glutenin polymers, dough properties and the end-use qualities of wheat cultivars.