Search

The Green Revolution gene sd1has been used extensively in modern rice breeding, especially in indicacultivars. However, elite sd1alleles and related germplasm resources used for japonicarice breeding have not been identified, and extensive efforts are needed for japonicarice breeding to obtain new dwarfing sources. Data from MBKbase-Rice revealed seven sd1haplotypes in indicaand four in japonicarice. Two new sd1alleles were identified in indicarice. In 295 japonicaaccessions from northeast Asia, except for the weak functional allele SD1-EQ, sd1-rwas the major allele, reducing plant height in comparison with SD1-EQ. Japonicagermplasm resources carrying reported sd1alleles were identified by genotype searching and further verified by literature search, genealogical analysis, and dCaps markers.Pedigrees and geographic distribution showed that sd1-ris an excellent allele widely used in northern China and Tohoku in Japan, and sd1-jis commonly used in east China and Kyushu in Japan. Dongnong- and Xiushui-series cultivars carrying sd1-rand sd1-j, respectively, are essential branches of the backbone parents of Chinese japonicarice, Akihikari and Ce21, with the largest number of descendants and derived generations. In semi-dwarf japonicarice breeding, sd1-dwas introgressed into Daohuaxiang 2 (DHX2). Dwarf and semi-dwarf lines carrying sd1-dwere selected and designated as 1279 and 1280, respectively, after withstanding typhoon-induced strong winds and heavy rains in 2020, and are anticipated to become useful intermediate materials for future genetic research and breeding. This work will facilitate the introduction, parental selection, and marker-assisted breeding, and provide a material basis for the next step in identifying favorable genes that selected together with the sd1alleles in japonicabackbone parents.