Registration of Durum Wheat Germplasm Lines with Combined Mutations in SBEIIa and SBEIIb Genes Conferring Increased Amylose and Resistant Starch.

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Durum wheat [Triticum turgidum L. subsp. durum (Desf.) Husn.], used in pasta, couscous, and flatbread production, is an important source of starch food products worldwide. The amylose portion of the starch forms resistant starch complexes that resist digestion and contribute to dietary fiber. Increasing the amount of amylose and resistant starch in wheat by mutating the STARCH BRANCHING ENZYME II (SBEII) genes has potential to provide human health benefits. Ethyl methane sulfonate mutations in the linked SBEIIa and SBEIIb paralogs were combined on chromosomes 2A (SBEIIa/b-A; Reg. No. GP-968, PI 670159), 2B (SBEIIa/b-B; Reg. No. GP-970, PI 670161), and on both chromosomes (SBEIIa/b-AB; Reg. No. GP-969, PI 670160) in the tetraploid wheat cultivar Kronos, a semidwarf durum wheat cultivar that has high yield potential and excellent pasta quality. These three double and quadruple SBEII-mutant lines were compared with a control sib line with no SBEII mutations in two field locations in California. The SBEIIa/b-AB line with four mutations showed dramatic increases in amylose (average 66%) and resistant starch (average 753%) relative to the control. However, the SBEIIa/b-AB line also showed an average 7% decrease in total starch and an 8% decrease in kernel weight. The release by the University of California-Davis of the durum wheat germplasm combining four SBEIIa and SBEIIb mutations will accelerate the deployment of these mutations in durum wheat breeding programs and the development of durum wheat varieties with increased resistant starch.