Allelic Variation Analysis Of The Rf3 And Rf4 Genes On Fertility Restoration In Rice With Wild Abortive Cytoplasmic Male Sterility

Rice is one of the major food crops in world.Hybrid rice breeding technology has made great contributions to improving food production,and the three-line hybridization technology has been widely used for a long time.Cytoplasmic male sterility and fertility of restoration system is the key to the production of three-line hybrid rice,and also the basis for the utilization of heterosis,and the effect of the restorer gene directly affects the selection of restorer lines,which in turn restricts the yield of the hybrid rice F1 generation.Therefore,the identification and analysis of the allelic variation of the restorer gene and fully exploiting and utilizing the excellent alleles for breeding the elite restorer lines,which have a great significance for the application and development of hybrid rice.In this study,the abundant alleles were identified at the loci of restorer genes Rf3 and Rf4 in respectively by using singlegene restorer lines(SGRLs)from a wide range of donor sources.The main results are as follows:1.Rf3 probably can affect the WA352 expression.During the analysis of the allelic variation of the restorer gene Rf3,the expression of WA352 was detected in the seedling leaves after transplating 20 days and 3-4 mm spikelet stage of pollen mother cell meiosis.Based on the results,it was speculated that Rf3 probably can affect the gene expression of WA352 at the transcriptional level.2.Analysis of allelic variation in Rf3 and Rf4 loci.The Rf3-SGRLs and Rf4-SGRLs were used to test-crosses with HXA,a cytoplasmic male sterile line,respectively.The phenotypic traits such as pollen fertility,spikelet fertility,spikelet elongation rate and the expression of the gene WA352 were analyzed.The phenotype and molecular expression levels were evaluated for their restorer ability.Finally,three allelic types were identified in the 2 gene loci.According to the restoration effect from weak to strong,Rf31,Rf32,Rf33 at the Rf3 locus and Rf4~1,Rf4~2,Rf4~3 at the Rf4 locus,respectively.3.Cultivation and identification of new sterile lines.In the process of allelic variation analysis of Rf3 and Rf4,based on allelic variation of rice restorer genes,a number of new sterile lines were found and identified,integrated pollen fertility,spikelet fertility,the rate of spikelet elongation with WA352 expression analysis,finally,four new sterile lines S1,S2,S3 and S4 and two new sterile lines L1 and L2 were found and identified on the base of the allelic variation of Rf3 and Rf4,respectively.These new sterile lines were investigated,which characterized by stable complete sterile during the two years in three generations.In this study,we identified the allelic variation of the wild abortive type cytoplasmic male sterility restorer genes Rf3 and Rf4 in rice by comprehensively analyzing the pollen fertility,spikelet fertility,spikelet elongation rate and the expression of WA352 on the basis of SGRLs.Combine the phenotype and molecular level,the types of excellent allelic variants of different restorer ability were identified.The results provided further theoretical and material support for the use of different alleles of Rf3 and Rf4 for three lines hybrid rice design breeding.