Elite sd1 alleles in japonica rice and their breeding applications in northeast China

The Green Revolution gene sd1 has been used extensively in modern rice breeding,especially in indica cultivars.However,elite sd1 alleles and related germplasm resources used for japonica rice breeding have not been identified,and extensive efforts are needed for japonica rice breeding to obtain new dwarfing sources.Data from MBKbase-Rice revealed seven sd1 haplotypes in indica and four in japonica rice.Two new sd1 alleles were identified in indica rice.In 295 japonica accessions from northeast Asia,except for the weak functional allele SD1-EQ,sd1-r was the major allele,reducing plant height in comparison with SD1-EQ.Japonica germplasm resources carrying reported sd1 alleles were identified by genotype searching and further verified by literature search,genealogical analysis,and d Caps markers.Pedigrees and geographic distribution showed that sd1-r is an excellent allele widely used in northern China and Tohoku in Japan,and sd1-j is commonly used in east China and Kyushu in Japan.Dongnong-and Xiushui-series cultivars carrying sd1-r and sd1-j,respectively,are essential branches of the backbone parents of Chinese japonica rice,Akihikari and Ce21,with the largest number of descendants and derived generations.In semi-dwarf japonica rice breeding,sd1-d was introgressed into Daohuaxiang 2(DHX2).Dwarf and semi-dwarf lines carrying sd1-d were 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 sd1 alleles in japonica backbone parents.

OsASHL1 and OsASHL2,two members of the COMPASS-like complex,control floral transition and plant development in rice

COMPASS or COMPASS-like is a highly conserved polyprotein complex in eukaryotes that is often involved in methylation of histone H3 lysine 4(H3K4).However,the biological function of this complex in rice(Oryza sativa)is unclear.Here,we report the identifiction of their functions in growth and development.The osashl1osashl2 double mutant shows a dwarf and late-flowering phenotype.Lower expression of Ehd1,OsVIL4,and OsMADS51 in the osashl1 osashl2 double mutant background accompanies a delayed vegetative growth phase and photoperiod-sensitive phase compared with that in wild type.Notably,there is less H3K4mono-,di-and tri-methylation genome-wide in the double mutant,in particular less H3K4 tri-methylation at OsVIL4.Consistent with this result,knockout of OsVIL4 gives rise to a late-flowering phenotype similar to that of the osashl1 osashl2 double mutant,suggesting that OsVIL4 is a target of the COMPASS-like complex.In addition,the expression of key genes in brassinosteroid and gibberellic acid metabolism is altered in the osashl1 osashl2 double mutant,suggesting that the COMPASS-like complex regulates plant growth and development by modulating the levels of these two phytohormones.In summary,we demonstrate that OsASHL1 and OsASHL2 are important for floral transition and plant development.