Genetically enhancing rice resistant starch, a dietary fiber, to combat chronic diseases

Authors: Pinson, Shannon; CHEN, MING-HSUAN - Retired ARS Employee; WANG, YA-JANE - University Of Arkansas; GONZALEZ, ANA - University Of Arkansas

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/29/2023
Publication Date: 10/29/2023
Citation: Pinson, S.R., Chen, M., Wang, Y., Gonzalez, A. 2023. Genetically enhancing rice resistant starch, a dietary fiber, to combat chronic diseases. ASA-CSSA-SSSA Annual Meeting, St. Louis, Missouri, October 29 - November 1, 2023. Meeting Abstract.

Interpretive Summary:

Technical Abstract: With increasing incidence of diabetes worldwide, rice breeders have become interested in developing varieties with lower glycemic index (GI) and increased dietary fiber to meet consumer demand for healthier food. Resistant starch (RS) resists digestion to glucose in the small intestine and passes to the colon as dietary fiber where it promotes the growth of health-beneficial microbiota. Higher RS results in lower-GI rice. Increased consumption of RS improves gut health and decreases cardiovascular disease With the goal of identifying novel genes and gene combinations that increase rice RS, we identified a novel starch mutant (KatyM) and used segregating cross progeny to evaluate its impact on RS individually, and in combination with alleles at genes previously shown to increase RS: WX-a which results in high grain amylose content, and non-functional starch branching enzyme 3 (sbe3) which results in higher average amylopectin chain-length. Using F2, F3, and F4 progeny, 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 F3:4 and F4:5 near-isogenic siblings marker-identified as homozygous for various combinations of SBE3/sbe3, KatyM/katyM, and high-/intermediate-amylose (WX-a/WX-in) were milled, cooked, and evaluated for RS content. The sbe3 mutation invoked the highest RS increase, with increased RS being related to a higher proportion of long amylopectin chains. When fixed for SBE3 and WX-a, the katyM mutation increased RS compared to KatyM/SBE3/WX-a progeny and increased RS was linked to a higher amylose:amylopectin ratio. The katyM and sbe3 mutations proved antagonistic rather than complimentary, with progeny containing both katyM and sbe3 having less RS than those containing sbe3 alone, possibly from a reduction in amylopectin with long chains. Low-GI, high-RS rice varieties can be developed using markers to select for WX-a, sbe3, and wild-type KatyM alleles.