Identification Of The Genes Conferring Resistance To Powdery Mildew In The Chinese Wheat Landraces

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most destructivediseases in wheat (Triticum aestivum L.). Host plant resistance is the most cost-effective and sustainablemeasure to control this disease. The development of powdery mildew resistant cultivars relies on theavailability of resistance genes. Chinese wheat landraces are rich in genetic diversity, which constitutesan important resource of powdery mildew resistance genes. The main objectives of this study were toidentify and localize effective genes for resistance to powdery mildew in Chinese wheat landraces forproviding potential new powdery mildew resisrant germplasms that can be used in wheat breeding.1. Using an F2population (264plants) derived from a cross between the wheat landraceHongyanglazi and the susceptible cultivar Zhongzuo9504and210corresponding F2:3families, geneticanalysis indicated that Hongyanglazi carried a single recessive gene, tentatively designated PmHYLZ,for its resistance to the Bgt isolate E09. PmHYLZ was flanked by microsatellite marker Xgwm46andEST marker BE606897on chromosome7BS at genetic distances of3.6cM and1.7cM, respectively.This gene differed from Pm40, also located on7BS, by origin, linked markers, and reactions to13isolates of Bgt. Based on these findings, the new powdery mildew resistance gene PmHYLZ has beenpermenantly designated Pm47.2. Genetic analysis and molecular mapping of powdery mildew resistance gene in the landraceJiantouhong were conducted on an F2population and the corresponding F2:3families derived from thecross Jiantouhong×Zhongzuo9504. A single recessive gene in Jiantouhong, temporarily designatedPmJ, conferred its resistance to Bgt isolate E09. This gene was flanked by microsatellite markerXgwm533and cfp1347on chromosome3BS at genetic distances of0.7cM and2.2cM, respectively.Since these markers were located in the distal bin3BS-9-0.57-0.75, PmJ must be located in the samechromosomal region. This gene differed from Pm13originated from Aegilops longissima, also locatedon3BS, in their origins, the modes of inheritance, and reactions to16Bgt isolates. Thus, PmJ is a newrecessive gene that is responsible for the resistance to powdery mildew in Jiantouhong.3. Using an F2population and the corresponding F2:3families derived from the crossBensanyuehuang×Zhongzuo9504, genetic analysis and molecular mapping were carried out toidentify the powdery mildew resistance gene in the wheat landrace Bensanyuehuang. A single recessivegene, PmB, proved to control the resistance of Bensanyuehuang to the Bgt isolate E09. By means ofSLAF-seq and Super-BSA, this gene was flanked by microsatellite marker Xbarc151and dCAPSmarker ESNP2on chromosome5AL at genetic distances of1.9cM and0.7cM, respectively. PmB wasco-segregated with the dCAPS marker ESNP1. This result demonstrates that SLAF-seq is fast andacurate means to localize the genes for disease rsistance in wheat.