Application Of The Broad Affinity Gene S₅ⁿ In Interspline Hybrid Rice Of Two Lines Of Indica-japonica Subspecies

Rice is one of the world’s most important food crops,and increasing rice yields is of great significance to ensure food security.Asian cultivated rice is divided into two subspecies,indica rice and japonica rice,because of the distant kinship between indica japonica subspecies,it has a strong hybrid advantage,so that indica japonica hybrids have great yield potential,becoming one of the main ways to further increase rice yield.Reproductive isolation is prevalent among Indica japonica subspecies,and the application of the broad affinity gene S₅ⁿ located on chromosome 6 of rice can effectively overcome fertility disorders.This makes it possible to exploit the heterogeneous advantage of the Indica japonica subspecies.This study was conducted mainly by studying 253 sterile lines and 13 containing the broad affinity gene S₅ⁿ The fruiting rate of 308 F₁ combinations in the recovery line was studied,and the rice broad affinity gene S₅ⁿ was analyzed The application effect in the interspecific hybrid rice of the two lines of Indica japonica subspecies,the main results are as follows:1.N418S of the phototemperature-sensitive nuclear sterile line was normally strong with some partial japonica and indica recovery lines,and N418S was detected by the molecular marker of the broad affinity gene S₅ⁿ.N418S does not carry the broad affinity gene S₅ⁿ,and further S₅ genotyping assays were determined to be S₅ of the Indica type S₅ genotype;Then,by intersecting with the variety of the Cantonese affinity test,the fruiting rate of the intercourse was investigated,and it was found that the fruiting rate of the sterile line N418S and the typical indica rice was 70%.Above,the hybridization with typical japonica rice is generally below 40%.The experimental results show that N418S does not have wide affinity,but is an indica rice sterile line with excellent traits.2.Using the existing molecular markers,the S₅ locus japonica typing test results were carried out on the existing 253 light-temperature sensitive nuclear sterile lines and breeding intermediate materials There were 51 materials containing homozygous broad affinity genes S₅ⁿ and 31 carrying S₅ⁿHeterozygous genes,171 without the S₅ⁿ gene;further to without the S₅ⁿgene 71 material indica-japonica typing was found,of which16 contained indica-type S₅ⁱS₅ⁱ,116 are japonica S₅^jS₅^j and 39 are indica hybrid S₅ⁱS₅^j.3.Taking Fengliangyou No.4 as the control,the seed setting rate of 308 F₁combinations carrying S₅ⁿ wide affinity and recovery line was investigated,and it was found that the combination with N19S-125,N19S-126 and N19S-127 as the sterile line combination had a setting rate of more than 60%except for individual combinations,especially with the recovery line R19001、R19008 and R19038,which exceeded the average setting rate of the control Fengliangyou No.4（73%）.The four recovery lines R19152、R27、R835 and RCDS have wide affinity and strong recovery ability,especially the recovery line R835 is the most prominent,and the average seed setting rate of the combination reaches 65.43%.4.The hybrid combinations of 308 F1 populations in 13 S5n-carrying broad affinity recovery lines were comprehensively analyzed for S5 site heterozygous genotypes and homozygous genotypes.The results showed that the fertility distribution of Indica japonica hybrid rice carrying homozygous broad-affinity gene S5n genotype was less affected by the indica japonica heterozygous background,the fluctuation range was relatively narrow,and the overall setting rate was stable.The fertility distribution of Indica japonica hybrid rice carrying the heterozygous broad-affinity gene S5n genotype was greatly affected by the background of Indica japonica,with a wide fluctuation range and a large span of fruiting rate.Overall,the S5n homozygous type has an overall high setting rate.5.In order to explore the effect of male semi-sterility gene on the additive effect of S5n fertility gene,the Sa gene of male sterility gene was identified in the key hybrid combination of F1 population,and it was found that there was no obvious accumulation and cumbersome effect between Sa gene and S5n fertility gene.This study can provide a production practice basis for the breeding of hybrid rice between two lines of Indica japonica subspecies,and is of great significance for accelerating the selection and utilization of strong dominant hybrid rice combinations between two lines of Indica japonica subspecies.