|Chen, Ming Hsuan|
Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/7/2020
Publication Date: 12/7/2020
Citation: Pinson, S.R., Chen, M. 2020. Increasing resistant starch in rice through genetics and breeding. ASA-CSSA-SSSA Annual Meeting. Abstract paper number 126455. Virtual Meeting, November 8-11, 2020.
Technical Abstract: Rice is unique among the major cereals as most of the crop is used directly for human consumption in the form of whole, milled kernels. As a staple food, rice is a major daily caloric source for billions of people globally. However, high incidence of diabetes worldwide reduces consumer interest in starch-rich foods. Breeders are interested in developing cereals with lower glycemic index (GI) and increased dietary fiber to meet consumer demand for healthier food. Resistant starch (RS), a starch fraction and a type of dietary fiber, resists digestion in the small intestines of healthy humans, and passes to the colon where it promotes the growth of beneficial gut microbiota. Dietary increases in RS can improve gut health and insulin response, and decrease risk factors for colon cancer and cardiovascular disease. Rice with increased RS would have lower GI and increased fiber. We identified a novel rice mutant (KatyM) from the cultivar ‘Katy’ that increased RS content as much as 70% (from 0.88 to 1.50%, DW). Grains from KatyM differed physicochemically from grains of ‘IR36M’ (a starch branching enzyme mutant (sbe3)) with high RS of 6%), suggesting the two genetic mutations were different. With the goal of further increasing RS and understanding the impact of multiple genetic variants on RS, the mutations were combined in progeny from a KatyM x IR36M cross. Using progeny homozygous for wild-type SBE3, the recessive katyM mutation was mapped to a 0.10 cM region of chromosome 8 containing the soluble starch synthase IIIa (ssIIIa) gene. Grains from F3 progeny marker-identified as homozygous for various combinations of SBE3/sbe3, KatyM/katyM, and high-/intermediate-amylose (Wxa/Wxint) were milled, cooked, and evaluated for RS content. Increasing amylose increased RS nearly 2-fold regardless of mutation genotypes, but progeny containing sbe3 alone had higher RS than progeny containing katyM and sbe3 combined.