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Biochemical Characterization of the Wheat Waxy A Protein and Its Effect on Starch Properties¹

¹NRCC No. 42618. ²National Research Council, Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, SK, S7N OW9, Canada. ³University of Saskatchewan, Crop Development Centre, 51 Campus Drive, Saskatoon, SK, S7N 5B1, Canada. ⁴USDA/ARS, Western Wheat Quality Lab, E-202 Food Quality Building, WSU, Pullman, WA 99164-6394. ⁵Corresponding author. Phone: 306-975-5574. Fax: 306-975-4839. E-mail: rchibbar@pbi.nrc.ca

Granule bound starch synthase1 (GBSS1) is a key enzyme in amylose biosynthesis and is encoded by the A, B and D GBSS1 wx loci in wheat. Wheat lines with mutations at the three GBSS1 loci have been identified. We have characterized and compared the grain starch of CDCW6 wheat line (null B and D for GBSS1) with PI235238 (null A and B for GBSS1), waxy (null A, B and D for GBSS1), and AC Reed (wild type wheat) grain starches. The grain starch of waxy, CDCW6, PI235238, and AC Reed lines contained ≈0, 12, 23, and 25% amylose (w/w), respectively. Waxy, partially waxy, and wild wheat grain starches showed significant differences in onset and peak transition temperatures as determined by differential scanning calorimetric analysis. Grain starches extracted from waxy, CDCW6, and PI235238 also had higher enthalpy of gelatinization values than did wild wheat starch. X-ray diffraction analysis revealed the highest crystallinity for starch extracted from waxy wheat, followed by CDCW6. The starch produced from the CDCW6 line may find special food and industrial applications because of its relatively low amylose concentration.