Genetic Analysis Of The Resistance Gene Of Wheat Germplasm N9659 To Powdery Mildew

Powdery mildew,caused by Erysiphe graminis f.sp.tritici,is one of the devastating diseases in wheat(Triticum aestivum L.em Thell.),and breeding for resistant cultivars have been proven the most effective way to control this disease.Screening for and utilization of diversified resistance genes are the foundation to carry on the resistance breeding programs successfully.The relative species of wheat are rich in resistance genes for powdery mildew disease.Understanding the inheritance of these resistance genes is essential for effective use of them.The advent of molecular markers and construction of molecular marker maps of wheat has facilitated the studies of there sistance genes.Molecular markers tightly linked to resistance genes not only facilitates the identification and mapping of resistance genes,but also can be used for markers-assisted selection(MAS)of resistant lines in breeding programs. In this paper,a powdery mildew resistance gene,originating from wild emmer(Triticum dicoccoides Thell)accession'AS846',was transferred to a common wheat line N9659.N9659 was highly resistant to the prevailing Erysiphegraminisf·sp·tritici Race in Shaanxi Province. The genetic analysis of N9659 was done in order to determine the inheritance of powdery mildew resistance in N9659.The reciprocal crosses F₁ between N9659 and the susceptible cultivar Shaan160 was highly resistant to the powdery mildew,the ratio of resistant plants and susceptible plants in F₂ progeny fitted the expected 3 to 1. All of F₁ between wheat nullisomic lines(or monosomiic lines)and N9659 were highly resistant to the powdery mildew.The ratio of resistantand susceptible plants in(Abbondanza 5BM×N9659)F₂ progeny did not fit the 3 to 1,and other F₂ progeny fitted the 3 to 1.The results indicated that the powdery mildew resistance of N9659 at seeding stage was controlled by a single dominant gene located on chromosome 5B.127 F₂ plants of the crosses Shaan 160×N9659 were used for SSR analysis,3 of 208 wheat SSR primer pairs WMS67,WMS408 and WMS604 generated polymorphic DNA fragments between the resistant plants DNA pools and susceptible plants DNA pools.By analyzing the polymorphic markers in these segregating populations,the SSR locus Xgwm67,Xgwm408,and Xgwm604 located on chromosome 5B were found to be linked to Powdery mildew resistance gene with the estimated genetic distance of 6.7cM,9.0cM and 17.3cM.Xgwm67,Xgwm408,Xgwm604 was mapped to chromosome 5BL by using C.S.ditelosomic sand nulli-tetrasomics,indicating that there cessive resistance gene in N9659 was located on the long arm of chromosome 5B.The resistance gene derived from the mother Aegilops umbelluata AS846,was different from the resistant genes reported now,so it was problely a new gene.Analysis of high molecular weight glutenin subunits compositions of N9659 and its parents by means of SDS-PAGE showed that N9659 derived elite subunits of 1 and 14+15 from its parent Shaanyou 225,thus having favorable processing quality and utilization value in production.Investigation of agronomic traits of derived lines from wild emmer wheat AS846 showed that derived lines and wild emmer wheat AS846 were featured with good agronomic traits and immunity to powdery mildew,hence having high utilization value.