Inheritance And Molecular Mapping Of Powdery Mildew Resistance Gene PmAc In Wheat-Agropyron Gaertn. Chromosome Translocation Line 5112-4

Powdery mildew, caused by Erysiphe. graminis f. sp. tritici, is one of the most important devastating diseases of common wheat worldwide. Breeding for cultivars with resistance to powdery mildew is the most economical, effective and environmentally safe way to control the disease. Wild relatives of wheat have constituted a large reservoir for powdery mildew resistance, and are a rich gene pool for disease resistance. The advent of molecular markers and construction of molecular marker maps of wheat has facilitated the studies on resistance genes. The objectives of the present study were to identify and tag powdery mildew resistance gene in 5112-4 with SSR makers. The main results obtained were as follows:1. 336 individuals a F2 population derived from between 5112-4 (resistant) and Jingshuang16 (susceptible) were analysed for the resistance pattern in 5112-4. Genetic analysis and chi-square test of phenotype of F2 population showed that the ratio of resistant and susceptible plants in F2 fitted the expected 3 to 1 ratio. The results indicated that powdery mildew resistance of 5112-4 at seeding stage was controlled by a single pair of dominant genes.2. DNA samples extracted from leaves of the F2 population were extracted and ten each of resistant and susceptible individuals DNA were pooled into two separate groups for bulked segregant analysis (BSA). PCR amplification with 513 primer pairs were used to screen polymorphic markers. Of the 36 polymorphic SSR markers, three (Xwmc219, Xwmc313 and Xbarc170) were shown linked with the powdery mildew resistance gene in 5112-4. Linkage analysis showed that these three markers have the estimated genetic distance of 17.99 cM, 16.13cM and 7.34 cM, respectively.To identify the molecular markers to the resistant gene, 36 of 513 wheat micrisatellite primer pairs generated polymorphic DNA fragments between the resistant and susceptible plants DNA pools. By analyzing the polymorphic markers in these segregating populations, the microsatellite locus located on chromosome 4A were found to be linked to the resistance gene with the estimate3. SSR markers Xwmc219, Xwmc313 and Xbarc170, were all mapped on wheat 4A chromosome and the only one powdery mildew resistance gene located on this chromosome is Pm16, but a SSR marker Xgwm159 mapped Pm16 to the short arm of 5B chromosome, with a genetic distance of 5.3 cM. The powdery mildew resistance gene in 5112-4, therefore, may be a new resistant and has the origin of Agropyon cristatum, and was designated as PmAc (Powdery mildew resistance gene from Agropyon cristatum) tentatively.