Evaluation On Stripe Rust Resistance Of Common Wheat Germplasm And Exploring The Novel Resistance Genes

Wheat stripe rust,caused by Puccinia striiformis West.f.sp.tritici,is one of the most important wheat disease.China is a big wheat-growing country,and the highly epidemic region of wheat stripe rust.Wheat production in China is threatened by stripe rust.At present,the simplicity of stripe rust resistance background in wheat cultivars have not changed although a lot of cultivars and breeding lines have been released.Identification of stripe rust resistances in wheat cultivars or breeding germplasm is very important for wheat improvment with stripe rust resistance.The objectives of this paper were to identify the seedling stripe rust resistance genes,to investigate the inheritance of stripe rust resistance and to tag the stripe rust resistance genes.The following results were obtained.1.Evaluation on stripe rust resistance of common wheat germplasm.Using three prevalent races of yellow rust CYR31,CYR32 and mixed races,which included CYR30,CYR31, CYR32,Hy46 and Shuiyuan11,the stripe rust resisitance of 106 wheat lines were evaluated by inoculated races.It was found that 20 lines showed immunity or high resistance to all the races,and 26 lines showed moderately resistance to all the races, whereas 26 lines showed moderately susceptible to one of the tested races,and 33 lines showed highly susceptible to all races.In this study,the order of the virulence of the races was Mixed races＞CY32＞CY31.2.At first,Study on slow rusting in wheat infected yellow rust in Sichuan basin.A total of 51 wheat lines were tested with the mixed yellow rust races including CYR29,CYR30, CYR 31,CYR32 and shuiyuan11 during two consecutive seasons.Based on the disease curves,these wheat lines could be divided into 5 distinct groups,designed as G1-highly resistance type with final disease severity(FDS)below 10%,G2 and G3-slow rusting type with FDS ranging from 10%to 40%,G4-highly susceptible with FDS more than 50%,and G5-high temperature resistance type.The FDS of G2,G3 and G4 types were closely related to the sowing time.Fourteen wheat lines with slow rusting and 6 lines with high-temperature resistance were indentified.FDS could be used as a reliable and simple indicator for the evaluation of slow stripe rust resistance in wheat breeding program.3.The inheritance of resistance genes in ICA31 and ICA70,which were derived from ICARDA(The international center for agricultural research in the dry areas,ICARDA, Syria),were analyzed by inoculated with the prevalent stripe rust races CYR31 and CYR32.Two sets of populations of Chuanmai28/ICA31 and Chuanmai28/ICA70 were tested with two races.The phenotype of the F₁,F₂ and BC₁ seedlings were analyzed for resistance to stripe rust races.It was observed that the resistance of ICA31 to races CYR31 and CYR32 was both controlled by one dominant gene.The resistance of ICA70 to race CYR31 was controlled by the complementary action of one dominant gene and one recessive gene,while its resistance to race CYR32 was controlled by one recessive gene. The inheritance of resistance in CI-66 and CI-9 derived from CIMMYT were analyzed. The phenotype of the F₁,F₂ and BC₁ from Chuanmai28/CI-66 and Chuanmai28/CI-9 were analyzed for resistance to CYR32.The results showed that the resistance in CI-66 was controlled by one dominant gene,and the resistance of CI-9 was controlled by a couple of recessive gene.Thus,the expression of resistance gene in ICA70 is related with physical races and background of susceptible parents.4.A novel resistance gene Yrp81 was located on 2BS.For identification of seedling resistance gene in P81,F₁ and F₂ populations of the cross P81/Chuanmai28 were inoculated with CYR32.The resistance gene in P81 was allelic analysis with Yr5,Yr10, Yr15 and Yr26.The polymorphic SSR and RGAP primers between resistant and susceptible plants were used for genotyping the F₂ populations.Linkage analysis was conducted with the Mapmarker3.0.It was showed that P81 carried a single dominant resistance gene to CYR32,designated as YrP81,and YrP81 was different from Yr5,Yr10, Yr15 and Yr26 by allelism analysis.The resistance gene YrP81 was closely linked to four SSR loci on the 2BS with genetic distances WMC25-19.7cM,Xgwm429-2.3cM, WMC770-3.5cM and Xgwm148-5.0cM.From 586 RGAP primers,we screened out two RGAP makers linked with YrP81 at genetic distance RG1(NLRR/XLRR)-3.5cM and RG2(Pto kin4/NLRR-INV2)-5.2cM,respectively.The order of centromere,markers and gene was -WMC25-RGA2-RGA1-Xgwm429-YrP81-WMC770-Xgwm148-centromere-.At present,three stripe rust resistance genes(i.e.Yr27,Yr31 and YrCN19)have been located on 2BS.Yr27 and Yr31 were viruses to CYR31 and CYR32.YrP81 was different from Yr27 and Yr31 in resistance reaction,and different from YrCN19 at molecular markers and pedigree origin,suggesting that YrP81 is a new stripe rust resistance gene.5.A new resistance gene YrICA56 was located on 2BS.There was a dominant gene in ICA56 derived from ICARDA to CYR32 by the evaluation of F₁ and F2 population from Chuanmai28/ICA56,and this gene was difference with Yr5,Yr10,Yr15 and Yr26 by allelism analysis.The resistence gene in ICA56 was designated as YrICA56,and it was tagged by using F₂ population developed from Chuanmai28/ICA56.After screening 183 wheat microsatellite primers,it was found that five markers were linked to the resistance gene YrICA56 with genetic distance Xgwm296-7.0cM,Xgwm210-14.1cM, Xgwm261-10.4cM,WMC503-16.6cM,and WMC112-4.5cM.The order among centromere, markers and gene is -WMC503-Xgwm261-Xgwm296-YrICA56-WMC112-Xgwm210 -centromere-.Based on the results of mapmaker 3.0 and MapDraw 2.0,the resistance gene-YrICA56 is located on 2DS.The stripe rust resistance genes Yr16 and YrKat had been located on 2DS,while Yr16 is an adult resistance gene and YrKat is temperature sensitive. Therefore,it suggested that YrICA56 could be a new stripe rust resistance gene.