Increased Grain Amylose and Resistant Starch in a Quintuple SBEII-Mutant Common Wheat

The starchy endosperm of the wheat kernel is a major source of carbohydrates worldwide. Starches with a higher proportion of amylose have greater content of resistant starch, a fermentable dietary fiber that can provide health benefits. A strategy to increase the levels of resistant starch is to pyramid mutations in the STARCH BRANCHING ENZYME II (SBEII) isoforms SBEIIa and SBEIIb in the three homoeologs present in the A, B and D genomes of common wheat. In this study we report the effect of four different combinations of five mutations in SBEIIa/b paralogs and homoeologs that were incorporated into the hexaploid wheat cultivar Lassik. Grain total starch content, relative amylose content, resistant starch content and starch viscosity parameters showed significant differences between mutant and wild-type genotypes. The quintuple mutant line (mutated SBEIIa/b in A and B genomes, and SBEIIa in D genome) presented 57% increases in amylose content (P < 0.01) and 1002% increases in resistant starch (P < 0.01) relative to the non-mutagenized control. In a field experiment, the quintuple mutant showed a 7.8% reduction in total starch (P < 0.01) and in a greenhouse a slight 7.0% reduction in kernel weight that was not significant. The quintuple mutant line also presented significant differences in starch viscosity parameters. The release of common wheat germplasm combining five SBEII mutations is expected to expedite the development of varieties with increased amylose and resistant starch content.