Genetic Analysis And Gene Mapping Of Three(Semi-)dwarf Genes In Rice

Plant height is one of the important agronomic traits affecting rice yield and directly affects lodging resistance of rice.The"green revolution gene"semidwarf 1?sd1?greatly increased the yield of rice.However,the single recessive dwarf gene utilization lead to the narrowness of genetic background,the limitation of heterosis and the lack of genetic diversity.Therefore,the discovery of new dwarf genes can broaden the genetic basis of rice dwarf breeding and further understand the molecular mechanism of rice plant height.The new semi-dwarf gene sdq and sde was isolated from local varieties of Qiannong and Te'ai,respectively and one unclearified dwarf gene dn from Zhejiang dwarf variety-CLA.In this study,Two near-isogenic line?NIL?of ZX5T with semi-dwarf gene sdq?t?and sde?t?were used in this research.The agronomic traits investigation,phenotypic observation,genetic analysis and gene mapping were carried out and fine mapping of semi-drawf gene sdq?t?and sde?t?were finished.The main results of this study were summarized as following:1.A semi-dwarf mutant Xinqianai with sdq?t?gene was isolated from the double dwarf mutant Qiannong.The NIL ZX5T-sdq?hereinafter referred to as sdq?was developed between high mutant ZX5T as the recurrent parent and Xinqianai as the donor parent.Compared with ZX5T,the internodes of sdq were generally shortened except the first internode,therefore,sdq was a dwarf mutant of"d6"type.Cell morphology observation showed that both the cells number and length of second internode of sdq were decreased significantly,indicating that the second internode shortening of sdq was determined by the reduction of cell number and length,and that its dwarf character was affected by cell division and elongation.Exogenous hormone treatment experiments showed that sdq was sensitive to GA₃ but not to BR.Genetic analysis revealed that the dwarf phenotype of sdq was controlled by a pair of recessive single genes.The sdq gene was further mapped to on chromosome 2 between Indel marker Q14 and I2567 at a physical distance of 99Kb through map-based cloning method.There were 12 predictive genes in the localization interval.Three variations of sdq were found in the intergenomic sequence of Os02g0480466,intron of Os02g0480800,and copy number of Os02g0479700 respectively through BSA sequencing and interparental sequencing in the located region.2.A semi-dwarf multi-tiller mutant Xinte'ai with sde?t?gene was isolated from the double dwarf mutantTe'ai.The NIL ZX5T-sde?hereinafter referred to as sde?was developed between high mutant ZX5T as the recurrent parent and XinTe'ai as the donor parent.Compared with ZX5T,the internodes of sde were proportionally shortened.Thus,sde is a semi-dwarf mutant of"dn"type.Cell morphology observation of sde internode showed that number of internode cells of sde decreased significantly,indicating that the shortening of internode cells of the mutant was caused by the decrease of cell number,and its dwarf character was affected by cell division.Exogenous hormone treatment experiments showed that sde was not sensitive to GA₃ and GR24.Genetic analysis revealed that dwarf phenotype of sde was controlled by a pair of recessive single genes.The SDE gene was finally mapped between InDel marker DE2 and dCAPS marker ME2 on chromosome 6 based on the 432 F₂ recessive plants of sde/NJ6,which physical distance is 58Kb.BSA sequencing and interparental sequencing in the located region found that only a nucleotide substitution?from C to T?at the 2102th bp in the first exon of Os06g0154200,converting the 702th arginine?R?into tryptophan?W?.In addition,Os06g0154200 has been reported as a kind of SLs-related gene D3,its mutants performed high-tillering and dwarf,which similar to sde.Therefore,we speculate that SDE is an allele of the multi-tillering dwarf gene D3.3.The dwarf gene dn?t?was derived from the local variety CongLaAi?CLA?of Zhejiang province.The NIL ZX5T-dn?hereinafter referred to as dn?was developed between high mutant ZX5T as the recurrent parent and CLA as the donor parent.The average plant height of the dwarf mutant dn was44.74cm.Exogenous hormone treatment experiment indicated that dn was sensitive to GA₃.Genetic analysis revealed that dwarf phenotype of dn was controlled by recessive gene.The dn?t?gene was preliminarily located on chromosome 3 through gene initial localization.