[P3] Abiotic Stress for Crop Production

[P3-38] Introgression of Dormant Gene Sdr4-k Improves Grain Quality of Sake Rice

*Nominated for Presentation Awards

^○Shinya Kanazawa¹, Maiko Iwano¹, Marouane Baslam², Shigeru Hanamata², Murat Aycan², Isao Hanashiro³, Kazuhiko Sugimoto⁴, Toshiaki Mitsui^1,2 (1.Graduate School of Science and Technology, Niigata University, Japan, 2.Faculty of Agriculture, Niigata University, Japan, 3.Faculty of Agriculture, Kagoshima University, Japan, 4.Institute of Crop Science, National Agriculture and Food Research Organization, Japan)

Rice is one of the most important factors in determining the quality of sake. The grain kernel of sake rice cultivars is characterized by the possession of a white cloudy tissue at the center, termed 'white core'. The white core is a critical trait that affects, among others, water absorbability for sake production, yet the mechanism of controlling the tissue formation of the white-core remains not fully understood.
In this study, we focused on Seed dormancy 4 (Sdr4-k) —derived from indica rice "kasalth"—as a potential regulator of seed dormancy as well as high temperature (HT)-induced grain chalkiness reduction at the ripening stage. Using a biotron speed-breeding system —with controlled light, temperature, tiller removal, and embryo rescue—, we precisely introgressed the Sdr4-k gene into the sake rice varieties "Koshitanrei" and "Gohyakumangoku", and we developed a BC₃ population, named "Koshitanrei Sdr4-k" and "Gohyakumangoku Sdr4-k" in six generations and 17 months.
Field assessment, gene expression, and brewing characteristics data indicated that plants carrying the Sdr4-k gene had similar brewing traits to the WT. Koshitanrei Sdr4-k subjected to HT had significantly higher grain quality and seed dormancy than the WT. Our data revealed that HT induced alteration of starch-related gene expression in Koshitanrei Sdr4-k and Gohyakumangoku Sdr4-k ripe seeds than WT.