International Rice Congress 2023
Published October 16, 2023 | Version v1
Conference paper Open

Unravelling genetic regions lowering Glycaemic Index (GI) in brown and milled rice

Authors/Creators

  • 1. International Rice Research Institute
  • 2. Swinburne University of Technology, Malborne, Australia
  • 3. IPK, Gatersleben, Germany
  • 4. Food and Nutrition Research Institute, DOST Compound Saliksik St, General Santos Ave, Taguig, 1630 Metro Manila, Philippines
  • 5. CSIRO, Canberra, Australia
  • 6. Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
  • 7. De La Salle University, Manila, Philippines
  • 8. National Institute of Agricultural Botany

Description

Developing rice varieties with low glycaemic index (GI) is vital to mitigate the spiking type II diabetes incidences in Asia where rice is staple diet. While most white rice have high GI, its whole grain form (brown rice) holds the higher nutrition offering lower GI. Employing 320 rice indica rice accessions, we integrated genome-wide association study (GWAS) with the transcriptome and methylome-wide studies to decipher the genetics of GI in brown and milled rice. In milled rice, a hotspot GI6.1 region, spanning neighbourhood genes of GBSS1 was identified differentiating the intermediate and high GI. For texture, a SNP (C˃T) at exon10 of GBSS1 showed its on influence final viscosity, independent of amylose content/GI. Gene regulatory network analysis highlighted the role of the non-starch polysaccharide pathway in lowering GI. The low GI lines were further confirmed through clinical in vivo studies. In brown rice, a unique haplotype 4 derived from Rc-IPT5 regulators (LOC_Os07g11020 and LOC_Os07g11050) spanning chromosome 7 conferring lower GI value, showing regions' significance in lowering GI within brown rice. Notably, germplasm lines containing the haplotype 4 were evidenced with higher level of true amylose (amylose 1, AM1), long chain amylopectin (AM2), while retaining the lower values of short chain amylopectins. This multi-omics approach thus allowed us to discover the varied genetic basis conferring lowering GI in brown and milled rice.

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