Molecular Mapping Of A Thinopyrum Ponticm-derived Gene For Resistance To Powdery Mildew In Wheat Line CH7086

Powdery mildew,caused by Blumeria graminis f.sp.tritici,is one of the major diseases of wheat worldwide.The use of resistant cultivars is the most economical,efficient and environmentally safe way to control this disease. Wild and cultivated relatives have been proven to be very useful to broadening gene pool of wheat.Thinopyrum ponticm,as a wild relatives of wheat,is a perennial decaploid species(2n = 10x = 70) in the tribe Triticeae, with a JJJJ^SJ^S of genome.It is known to possess a number of elite genes for wheat improvement,such as those for rust resistance,wheat curl mite resistance,wheat streak mosaic virus(WSMV) resistance,barley yellow dwarf virus(BYDV) resistance,and tolerance to abiotic stresses,such as salinity and drought.Th.ponticum was found to be immune to many powdery mildew isolates,but no gene introgression has been reported to date.A new wheat line CH7086 is a source of multi-resistance to both powdery mildew and yellow rust,which derived from a hybrid of wheat-Th,ponticum partial amphiploid Xiaoyan7430 with susceptible wheat cultivars.The aims of thi study were to determine the inheritance,chromosomal location,and linkage with molecular markers of genes for resistance to powdery mildew in the Th. ponticum-derived multi-resistant germplasm line CH7086.1.To determine the inheritance and chromosomal location of powdery mildew resistance gene,CH7086 was crossed with a susceptive wheat cultivars "CH5421","Jintai170"and"Mianyang11".The seedling and adult tests of F₁,F₂ progeny plus parents were inoculated with Egt isolate E09 in greenhouse.F₁ plants were consistent with their resistant parent CH7086 and resistant to Pm.In the F₂ populations,the observed phenotypic classes for powdery mildew reaction satisfactorily fitted a 3R:IS segregation ratio, suggesting that the resistance was controlled by a single dominant gene.The gene was temporarily designated as PmCH.2.By bulk segregation analysis,two microsatellite markers Xbarc159 and Xwmc149 on chromosomal arm 2BLwere found to be linked to PmCH with genetic distances of 6.7 cM and 20.1 cM respectively.The marker and the Pm gene were assigned to chromosome 2BL by means of Chinese Spring Nullitetrasomic(Nulli2B-tetra2A,Nulli2B-tetra2D,Nulli2A-tetra2B) and ditelosomic(Dt2BL) lines.A detached leaf test showed a distinctive disease reaction to two pathogen isolates among the PmCH gene,Pm6(2BL) and Pm33(2BL).Based on the chromosomal locations and the resistance patterns of the gene,it was proposed that PmCH derived from Thinopyrum ponticum, is a new gene for resistance to powdery mildew in wheat.