The relationship of protein composition to end-product functionality of hard white wheat

by Gehlhar, Sarah Bronwen

Improving quality of hard white wheat (HW) cultivars in the Pacific Northwest is

important to expand exports to Asia. Asian food processors prefer HW grain that

can satisfy an array of baking needs, as well as produce superior quality noodle

products. Three experimental populations were developed from single cross and

backcross combinations of four parents with contrasting protein composition, bread-making

attributes, and noodle quality. Three hundred-sixty F?-derived F? progeny

grown in Corvallis, Oregon in 2004 were evaluated for protein content, single kernel

characteristics, milling yield, dough mixing properties, SDS sedimentation volume,

and polyphenol oxidase activity. Variation in flour protein composition was

determined by SE-HPLC and SDS-PAGE. The populations and progeny showed

wide variations in quality. Ranges in protein composition and mixing properties

exceeded those of the parents. Backcrossing had a significant influence on quality

characteristics of progeny. Progeny with the Glu-D1 HMW glutenin subunit (GS)

pair 5+10 had increased SDS sedimentation volume, mixing time, and tolerance as

compared to those with HMW-GS 2+12. At the Glu-B1 locus, HMW-GS 7+9 was

associated with improved protein quality and mixing properties as compared with

either 7+null or 6+8. The Glu-A1 HMW-GS 1 was associated with increased mixing

time and tolerance as compared with 2*; both of which had improved mixing

properties as compared with progeny carrying the null allele at this locus. Changes

in relative proportions of polymeric and monomeric proteins were associated with

variation in HMW subunit composition. Five LMW-GS were found to be

polymorphic in parents and progeny. The LMW-GS designated band-a, which had

relatively higher molecular weight, was associated with increased protein quality and

stronger dough handling properties. LMW-GS bands b and e were associated with

reduced mixing time and tolerance and lower levels of monomeric proteins.

Interactions of HMW and LMW subunits were generally associated with changes in

magnitude of effects rather than change in rank. Influences of LMW-GS were more

pronounced in progeny which carry HMW-GS associated with reduced dough

strength, such as 2+12, 7+null, or 2*. Manipulation of protein composition can be an

effective method to improve end-use quality of HW cultivars in the Pacific

Northwest.