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Increasing resistant starch content in wheat grain using TILLING.
B. HAZARD (1), X. Zhang (1), M. Naemeh (1), J. Dubcovsky (1). (1) University of California, Davis, Davis, CA, U.S.A.

Wheat (<i>Triticum aestivum </i>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 TILLING (Targeted Induced Local Lesions IN Genomes) mutants in the tetraploid durum wheat variety Kronos (<i>T. turgidum </i>ssp. <i>durum </i>L.) carrying mutations in the A and B genome <i>SBEIIa</i> and <i>SBEIIb </i>homoeologs and generated double <i>SBEIIa-SBEIIb </i>mutants to study the effect on amylose and resistant starch content.  Genotypes with both A genome <i>SBEIIa-SBEIIb </i>mutations in combination with B genome <i>SBEIIa-SBEIIb </i>mutations showed an approximately 66% increase in amylose content and approximately 680% increase in resistant starch content on average across two locations.  We are currently testing these mutants in three yield and quality trials across California.

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