Combined Mutations in SBEIIa and SBEIIb Genes in Durum Wheat Increase the Amylose and Resistant Starch Content in the Grain

Wheat (Triticum aestivum L.) is an important source of carbohydrates, proteins, fats, vitamins and minerals that contribute to a healthy human diet and provides approximately 20% of the calories consumed worldwide.  Starch is the major component of the wheat kernel (~50-70% of its dry weight), thus any improvements in its nutritional composition have the potential to deliver nutritional benefits. Starch in the wheat grain consists of amylopectin (~70-80%) and amylose (20-30%), which are both polymers of glucose molecules. Amylopectin is highly-branched and readily digested whereas amylose has few branches and forms complexes that resist digestion and contribute to dietary fiber (resistant starch). As with fiber, increased consumption of resistant starch has been associated with reduced risk of diseases such as diabetes, obesity, heart disease, and cancers of the colon and rectum. We previously obtained ethyl methane sulphonate mutants in the tetraploid durum wheat variety Kronos (T. turgidum ssp. durum L.) carrying mutations in the A and B genome SBEIIa and SBEIIb homoeologs and generated double SBEIIa-SBEIIb mutants to study the effect on amylose and resistant starch content.  Genotypes with both A genome SBEIIa-SBEIIb mutations in combination with B genome SBEIIa-SBEIIb mutations showed an approximately 66% increase in amylose content and approximately 680% increase in resistant starch content on average across two locations.