Allelic variation at Glu-D1 locus for high molecular weight (HMW) gluteninsubunits: Quantification by multistacking SDS-PAGE of wheat grown under nitrogen fertilization

Two biotypes of an Australian wheat cultivar, Warigal, differing only in th e Glu-D1 high molecular weight (HMW) glutenin subunits 5+10 and 2+12 were u sed in this study. The objective was to examine the effects of nitrogen fer tilization and allelic variation at the Glu-DI locus on the characteristics of glutenin polymers. Unreduced proteins containing the SDS-soluble gluten ins and the other protein classes were analyzed by multistacking SDS-PAGE w hich separates the glutenin into six distinctly different-sized aggregates. The results showed that nitrogen fertilization significantly increased pro tein quantity, ratio of polymers to monomeric proteins, and sizes of SDS-so luble glutenins. Nitrogen fertilization affected the proportions of HMW sub units in both SDS-soluble and SDS-insoluble glutenin polymers and the ratio of x to y subunits in SDS-insoluble glutenin polymers. Nitrogen fertilizat ion, however, did not cause a significant change in ratio of SDS-soluble to SDS-insoluble glutenins. SDS-insoluble glutenins had a greater ratio of HM W to LMW and x to y subunits, especially with a higher increase of 1Dx subu nits, than SDS-soluble glutenins. The HMW/LMW subunit ratio and the x/y sub unit ratio may be used to predict sizes of glutenin polymers. The biotype w ith 5+10 subunits had a greater x/y subunit ratio in the SDS-insoluble glut enins than the 2+12 type. A greater proportion of subunit 5 was formed than subunit 2 in the SDS-insoluble glutenin polymers. Both nitrogen fertilizat ion and allelic variation at Glu-DI loci could affect the characteristics o f glutenin polymers.