Deficiency of individual high molecular weight glutenin subunits affords flexibility in breeding strategies for bread-making quality in wheat Triticum aestivum L.

High-molecular-weight (HMW) glutenin subunits in wheat Triticum aestivum L. , allelic variation for which affects bread-making quality, are encoded by Glu-1 homoeoloci located on the homoeologous group 1 chromosomes. Many alle les at Glu-B1 and Glu-D1 produce two subunits, an x-type of low electrophor etic mobility in polyacrylamide gels, and a y-type of high mobility. In the current study, a combination of near isogenic lines of cultivar 'Sicco' ha s been used to characterise the effect upon quality of the absence of indiv idual subunits 7 ( Glu-B1 x-type), 12 ( Glu-D1 y-type) and, assuming an add itive model of subunit action, 2 ( Glu-D1 x-type). Absence of subunit 7 gav e a moderate reduction in SDS-sedimentation volume, indicating its associat ion with lower gluten strength (confirmed by Farinogram and Extensogram stu dies), yet, from a full mixing input bake, a moderate increase in loaf volu me and a considerable improvement in loaf score (an overall evaluation of l oaf quality). Absence of subunit 12 gave a slightly larger reduction in SDS -volume, yet no change in loaf volume or score. Absence of both subunits 212 gave a larger reduction again in SDS-volume, a moderate reduction in loa f volume and a large reduction in loaf score. Absence of subunit 2 alone is therefore predicted to reduce SDS-volume, loaf volume and score such that loss of this x-type subunit would lead to larger changes in quality paramet ers than loss of y-type subunit 12. A general conclusion of the study is th at, while deficiency for HMW glutenin subunits generally leads to reduced g luten strength and viscoelasticity, the resultant intermediate gluten stren gth may on occasions lead to improvements in loaf performance in situations where the base gluten strength is high. There may, then, be contexts in br eeding programmes where selection for deficiency would be a possible strate gy for improving bread-making quality, adding to the flexibility available to the breeder. Somewhat unexpectedly, additional analysis found that, in t he genetic background of cultivar 'Sicco' used in this study, subunits 7+8 at Glu-B1 were indistinguishable from their allelic counterparts subunits 7 +9 for virtually all characters, and that subunits 2+12 at Glu-D1, while in ferior in performance for mixing properties compared to subunits 5+10, were associated with good loaf characteristics.