ROLE IN DOUGH RHEOLOGY OF HIGH-MOLECULAR-WEIGHT GLUTENIN SUBUNITS OF SOFT WHITE WINTER AND CLUB WHEATS

The effect of high molecular weight glutenin subunit (HMW-GS) composit ion of seven soft white winter (SWW) and four club wheat cultivars fro m the Pacific Northwest region on dough rheology was investigated. All samples were harvested in 1988, 1990, and 1993 (in Walla Walla, WA). Three selected SWW and three club wheats were grown in 1990, in seven locations covering broad growing conditions. The SWW and club wheats g rown under the same conditions showed similar protein content (11.70 a nd 11.65%, respectively) but distinctly different values of total area of HMW-GS (0.9-1.9 for SWW, and 0.7-1.3 for club wheat, excluding Hya k). The quality score of HMW-GS multiplied by area showed much better correlation with dough rheology (alveograph W: r = 0.905; mixograph mi xing time: r = 0.743) and SDS sedimentation volume (r = 0.883) than fo r each of these parameters separately. The increase in protein content of SWW, (from 8.5 to 12.5%) and of club wheats (from 7.5 to 11%) resu lting from growing conditions accompanies the increase of total area o f HMW-GS, from 0.85 to 1.3 and from 0.7 to 0.95, respectively. However , that increase better matched the increase in protein content of SWW wheats (r = 0.662) than club wheats (r = 0.352). If the increase in pr otein content is substantial for the cultivars with high quality score HMW-GS, it might cause an increase of gluten strength as measured by dough rheology and SDS sedimentation value. The cultivar Hyak, contain ing the subunits 7+8 in Glu-IB locus and 5+10 in Glu-ID locus, is a go od example of the latter. The club wheats (not Hyak), having a general ly low quality score of HMW-GS, preserve unique properties of weak glu ten, even with the increase of protein content.