Effects of homoeologous wheat starch synthase IIa genes on starch properties.

Near-isogenic lines (NILs) of the eight haplotypes of starch synthase IIa (SSIIa) were used to analyze the effects of SSIIa gene dosage on branch chain length, gelatinization, pasting, retrogradation, and enzymatic hydrolysis of starches. Compared to wild-type, the amylopectin of lines missing one or more active SSIIa enzymes had increases in the proportion of short branch chains (DP6-10) and decreases in midlength chains (DP11-24), and the size of these differences depended on the dosage of active SSIIa enzymes. Of the three loci, SSIIa-A1 had the smallest contribution to amylopectin structure and SSIIa-B1 the largest. The different effects of the three SSIIa enzymes on starch properties were also seen in gelatinization, retrogradation, pasting, and enzymatic hydrolysis properties. Such differences in starch properties might be useful in influencing the texture and shelf life of food products.