Development Of New Wheat EST-SSR Markers And Molecular Mapping Of Salinity Tolerance Genes

Identification of salinity tolerance genes from Chinese wheat landraces and development of new wheat cultivars with tolerance is the most effective way to use the salinity soil.A group of new wheat functional markers was developed based on ESTs from NCBI databases and was mapped using a set of wheat nulli-tetra disomic lines.New wheat germplasm with salinity tolerance of some landraces from Southern China was identified and genetic polymorphism was analyzed by gSSR markers.Using BSA method,the major gene controlling salinity tolerance of Sizimai was mapped and the result was as the following. Of 81 pairs of EST-SSR primers developed from salinity stressed cDNA library etc, 67(82.72%),49(60.49%),18(22.22%) and 61(75.31%) produced stable amplicons in genomes of wheat,rye,Haynaldia villosa and barley,respectively.Additionally,22(32.83%) produced polymorphic loci between wheat Chinese Spring and Huixianhong,and 23(37.71%) between barley Silengdamai and Kuanyingluomai using a set of wheat nulli-tetrasomic lines(except N3D and N6D).43 markers with 81 loci were mapped in 18 chromosomes except 3D,4B and 6D.Of them,30 were positioned on genome B,29 on A and 22 on D,respectively.Loci mapped in different homoeologous groups showed an order as 2＞1＞7＞4＞3＞6＞5.These new markers will be very useful in comparative genetics,gene mapping and genetic diversity study in wheat and its relatives.Salinity tolerance in germination and seedling of 68 Chinese wheat landraces was identified and 3 new germplasm with tolerance in germination and 1 in seedling were found.Genetic distances of 30 landraces revealed by 40 gSSR markers varied from 0.22-0.74 averaged at 0.46.Based on this parameter,these landraces were divided into three groups after clustering analysis.The first group included 6 landraces such as Sizimai etc.The second included 21 such as Heshangmai etc.The third includes 3 ones such as Daheshangtou, Tubamai and Wugongmai.Reciprocal cross combinations were made between Sizimal and Heshangmai.Salinity test indicated that both Sizimai and the reciprocal F₁ all showed stable tolerance,while Heshangmai could not germinate at 250mmol·L^-1NaCl.Among 2441 F₂ seeds,segregation of tolerance and non-tolerance completely followed 3:1.Of 410 wheat gSSR and eSSRs, 144 markers produced polymorphic amplicons between Sizimai and Heshangmai,and 2 of them(Xgdm5 and SCM158) also showed polymorphism beween the resistance and sensitive pools while only Xgdm5-2DS showed significant correlation with salinity tolerance(r=0.49,P＜0.0001).Using Mapmaker3.0,integrated with other 2 polymorphic markers Xgwm296 and Xwmc112 of 2DS between the two parents,the major gene controlling salinity tolerance of Sizimai were preliminarily mapped on 2DS closely linked to Xgdm5 with distance 6.9 cM.