Microsatellite Mapping of a Powdery Mildew Resistance Gene in Wheat Landrace Xiaobaidong

Xiaobaidong, a Chinese landrace of wheat (Triticum aestivum L.), is resistant to a wide spectrum of powdery mildew (Blumeria graminis f. sp. tritici, Bgt) races, especially effective to currently prevalent races. This variety shows a response pattern that is different from the varieties possessing the documented Pm genes after inoculation with 10 isolates of different virulence. Genetic analysis indicated that the single recessive gene, mlxbd, was responsible for the powdery mildew resistance at seedling stage. The adjacent molecular markers of the gene was located using 2 mapping populations derived from the reciprocal crosses between Xiaobaidong and a susceptible cultivar Chancellor with 125 and 107 individuals of the F2 generation. The resistance gene mlxbd was found between the microsatellite markers Xgwm577 and Xgwm1267 on chromosome 7B, and located on the distal bin of chromosome 7BL-10 (Bin 0.78–1.00) using the Chinese Spring nullisomic-tetrasomic, ditelosomic, and deletion lines. To verify the efficiency of the microsatellite markers that might be used in molecular marker-assisted selection (MAS), genomic DNA of 23 wheat genotypes with known resistance genes were amplified by Xgwm577, the proximal marker of mlxbd. The result showed that Xgwm577 was able to differentiate resistance genes originated from Chinese varieties with Pm5a and Pm5b except for PmH; however, resistance genes near Pm5 locus were not identified with Xgwm577. This indicates that Xgwm577 should be combined with other markers in MAS.

摘 要小麦农家品种小白冬麦对小麦白粉病具有良好抗性, 对病原菌拥有较广的抗谱, 并与其他已知抗白粉病基因的抗谱不同, 遗传分析证实小白冬麦的苗期抗性由一个隐性抗白粉病基因控制。为了寻找与小白冬麦所携带抗白粉病基因连锁的分子标记, 采用小白冬麦和感病品种Chancellor (CC)正反交组合, 在2个F2群体125和107个单株上进行验证。结果显示, 抗白粉病基因mlxbd与引物Xgwm577、Xgwm1267等紧密连锁, 通过中国春及其第7部分同源群缺体-四体系, 双端体系和缺失系将其定位在7B染色体长臂末端区域(7BL-10, Bin 0.78∼1.00), 利用与mlxbd最近的引物Xgwm577扩增23个含有已知抗白粉病基因的小麦品种, 检测发现这个引物不能单独用于分子标记辅助选择育种。