Published as: Crop Sci. 2012 ; 52(4): 1754–1766.

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Induced mutations in the starch branching enzyme II (SBEII) genes increase amylose and resistant starch content in durum wheat Brittany Hazard, Dept. of Plant Sciences, University of California, Davis, CA 95616, USA Xiaoqin Zhang, Dept. of Plant Sciences, University of California, Davis, CA 95616, USA Pasqualina Colasuonno, Dept. of Plant Sciences, University of California, Davis, CA 95616, USA

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Cristobal Uauy, Dept. of Plant Sciences, University of California, Davis, CA 95616, USA Diane M. Beckles, and Dept. of Plant Sciences, University of California, Davis, CA 95616, USA Jorge Dubcovsky* Dept. of Plant Sciences, University of California, Davis, CA 95616, USA Howard Hughes Medical Institute Chevy Chase, MD, USA

Abstract

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Starch is the largest component of the wheat (Triticum aestivum L.) grain and consists of approximately 70-80% amylopectin and 20-30% amylose. Amylopectin is a highly-branched, readily digested polysaccharide, whereas amylose has few branches and forms complexes that resist digestion and mimic dietary fiber (resistant starch). Down-regulation of the starch branching enzyme II (SBEII) gene by RNA interference (RNAi) was previously shown to increase amylose content in both hexaploid and tetraploid wheat. We generated ethyl methane sulphonate (EMS) mutants for the SBEIIa-A and SBEIIa-B homoeologs in the tetraploid durum wheat variety Kronos (T. turgidum ssp. durum L.). Single-gene mutants showed non-significant increases in amylose and resistant starch content, but a double mutant combining a SBEIIa-A knock-out mutation with a SBEIIa-B splice-site mutation showed a 22% increase in amylose content (P