Starch is the major component of the wheat grain. It is composed of amylopectin ("70-80%) and amylose ("20-30%). The ratio of these two glucan polymers, along with morphological traits, have an effect in its digestibility. Starches that are resistant to digestion are an important component of dietary fibre capable of delivering a range of health benefits. Given that nearly 20% of the calories consumed globally come from wheat, further improvements in its nutritional value have the potential to make a large health impact. Understanding the key genetic components of starch biosynthesis is required. The amylose and amylopectin are synthesised by three groups of enzymes: starch synthases (SSs), starch branching enzymes (SBEs), and starch debranching enzymes (DBEs). While SSs are known to elongate the glucan chains, the effect of mutations in wheat SSIII genes is still poorly understood. In this study, Starch Synthase IIIa (SSIIIa) has been targeted for knockout mutations using Targeting Induced Local Lesions In Genomes (TILLING) in wheat. Different combinations of homoeologues mutations in hexaploid wheat are likely to yield starch phenotypes with novel properties and provide useful candidate germplasm for developing high-resistant starch traits. This provides an opportunity for fine-tuning the design of healthier wheat starches.

THEME 4