Resistance of 'Zhongmai 155' Wheat to Powdery Mildew: Effectiveness and Detection of the Resistance Gene

Powdery mildew, caused by the biotrophic parasitic fungus Blumeria graminis f. sp. tritici (Bgt), is a prevalent disease in many wheat (Triticum aestivum L.)-producing regions throughout the world. To reduce yield losses and avoid environmental pollution caused by fungicide application, growing resistant cultivars is the preferred means for managing wheat powdery mildew. 'Zhongmai 155', a commercial winter wheat cultivar released in 2012, was resistant to 92 of the 115 Bgt isolates originating from northern China. Using segregating F-2 and F-2:3 populations derived from Zhongmai 155 x 'Han 4564' cross, genetic analysis indicated that a single dominant resistance gene, tentatively designated PmZ155, was responsible for the resistance of Zhongmai 155 to the Bgt isolate E09. The gene was subsequently localized on chromosome 5DS on the basis of the results of molecular marker analysis. The flanking markers SCAR203 and Xcfd8 are linked to gene PmZ155 at genetic distances of 0.3 and 4.9 cM, respectively, and were physically mapped to the deletion bin 5DS-1-0-0.63; therefore, PmZ155 is located in this region of chromosome 5DS and shares the same molecular markers as Pm2. However, Zhongmai 155 differed from Ulka/8*Cc (CI 14118), which carries gene Pm2 on chromosome 5DS, in its reactions to 26 of 111 commonly tested isolates, of which 18 isolates were avirulent on Zhongmai 155 but virulent on Ulka/8*Cc, while 8 isolates were virulent on Zhongmai 155 but avirulent on Ulka/8* Cc. Zhongmai 155 also differed from 'Tabasco' (carrying Pm48 on chromosome 5DS) in its reaction to 14 of 62 isolates. On the basis of its chromosome position, close linkage to the molecular markers Xcfd8 and SCAR203, but different responses to an array of Bgt isolates, it appears that PmZ155 is most likely an allele of locus Pm2.