ADDITIVE AND EPISTATIC EFFECTS OF ALLELIC VARIATION AT THE HIGH-MOLECULAR-WEIGHT GLUTENIN SUBUNIT LOCI IN DETERMINING THE BREAD-MAKING QUALITY OF BREEDING LINES OF WHEAT

The relation has been studied between the high molecular weight glutenin (HMWg) subunit alleles and the bread-making quality of 226 lines of winter wheat (T aestivum L.), grown in The Netherlands. The lines represented a wide range of genetic backgrounds, and had not been selected for quality, in contrast to the established varieties used by other authors. The variation in HMWg subunit genotypes accounted for about 20% of the total variation in loaf volume among the lines. Most important was the allelic variation at the Glu-D1 locus. The Glu-D1 allele encoding the subunits 5 + 10 was superior to its allelic counterpart, encoding 2 + 12. The difference in average of loaf volume between groups of lines containing 5 + 10 or 2 + 12 was negatively related with protein content of the flours. When protein content was below 9.2%, no effect of allelic variation at the Glu-D1 locus was present. Epistatic effects between the Glu-I loci also contributed to the variation in loaf volume of the lines: i.e. the effect of allelic variation at Glu-A1 and Glu-B1 depended on the allele present at the Glu-D1. The contribution of the epistatic effects was about half the contribution of the additive effects, and should therefore be included in predictive models for bread-making quality.