Genetic Analysis And Mapping Of Fertility-restorer Genes For WA Type Cytoplasmic Male Sterile Line Of Japonica Rice(Oryza Sativa L.)

WA type Cytoplasmic Male Sterile (CMS -WA)lines have being widely applied to hybrids of indica rice,but restorer lines were hardly found when CMS -WA was transferred into japonica rice.In the process of screening for restorer lines for widely-compatible isonuclear-alloplasmic japonica CMS lines,a strong broad-spectrum restorer line 6078,which could well restore the fertility of CMS -WA line of indica or japonica rice ,was found by the institute of Yangzhou University.So it would provide valuable restoring resource for the breeding of hybrid of japonica rice by use of CMS -WA.In this research, the widely-compatible japonica CMS -WA line zhenqiuA and the indica CMS -WA line zhenshan97A were hybridized with 6078 respectively.The cross of F1,F2,BC1F1 and three-setting F1 was deployed to compare the the fertility inheritance of CMS -WA line of japonica rice with that of indica rice.Moreover, the restorer genes in 6078 were mapped primarily.In order to get rid of the influence of cross-sterility caused by hybrization between indica and japonica, F2 population between zhenqiuB and 6078 was studied. In addition,the proportion of Typical Abortive(TA) pollen and Normal pollen acted as the fertility indexs and typical sterile group or normal fertile group was classified in segregative population according to the pollen fertility of parent or F1 hybrid. The results were as follows:(l)The abortive-pollen type of WA zhenshan97A were dominated by TA pollen,and WA zhenqiuA's sterility was more excessive with 100% TA pollen.(2)Because of widely-compatible gene in WA zhenqiuA, cross-sterility caused by non-compability between indica andjaponica was avoided . the inheritance analysis of fertility-restorer for WA zhenqiuA/6078 wouldn't be influenced.(3)There were 3 pairs of genes responsible for the fertility inheritance of WA zhenshan97A/6078.Apart from Rf-3 and Rf-4 genes which were existing in most of other restorer lines ,there was another restoring gene Rf-a with the lowest restoring ability which only could improve the abortive degree of pollen in 6078. Rf-a gene could decreased the proportion of TA pollen but could enhance the restoring ability when it functioned together with Rf-3 and Rf-4 genes.(4)Besides the 3 pairs of restoring genes above,there was another domitant gene,inhibiting gene I in zhenqiuA which was also responsible for the fertility-restoring of WA zhenqiuA.Deduced by the proportion of typical sterile plants and normal fertile plants in segregative generations derived from WA zhenqiuA/6078 that:I gene could inhibit the expression of Rf gene completely by the heterozygosity of 1 pair of Rf in genotype;and only reduce the expression of Rf genes with two heterozygous Rf genes in genotype ;but it would never inhibit the expression of Rf genes if the genotype included 3 pairs of heterozygous Rf genes. When Rf gene was homozygous,the / gene could not inhibit the expression of it.So when a japonica CMS-WA line (rf-3rf-3rf-4rf-4 rf-arf-aII) was crossed with a normal restorer line for a indica CMS-WA line (Rf-3Rf-3Rf-4 Rf-4rf-arf-aii} ,the fertility of hybid FI (Rf-3rf-3Rf-4rf-4rf-arf-arf-ali)was not easily restored,but when the japonica CMS-WA line (rf-3rf-3rf-4rf-4 rf-arf-all) was crossed with 6078(Rf-3Rf-3Rf-4Rf-4Rf-aRf-aii),the hybid F1 could produce seeds normally.(4)By SSR analysis of the population consisting of 150 excessive sterile plants from F2(WA/6078), RM171(OSR33)which was located on the long arm of chromosome10,was linked closely to a restorer gene, the genetic distance between RM171 and therelated restoring gene was calculated as 3.67cM.Referring to the location of restorergene on chromosome 10 mapped by some other scholars ,the restoring gene might be Rf-4.