The effectiveness of wheat cultivar Liangxing 99 against powdery mildew was shown to be controlled by a single dominant gene located on a new locus of chromosome 2BL in the bin 2BL2-0.35-0.50. Liangxing 99, one of the most widely grown commercial cultivars in the winter wheat (Triticum aestivum) producing regions in northern China, was shown to provide a broad spectrum of resistance to Blumeria graminis f. sp. tritici (Bgt) isolates originating from that region. Using an F2 population and F2:3 lines derived from a cross of Liangxing 99 × Zhongzuo 9504, genetic analysis demonstrated that a single dominant gene, designated MlLX99, was responsible for the resistance of Liangxing 99 to Bgt isolate E09. The results of molecular analysis indicated that this gene is located on chromosome 2BL and flanked by the SSR marker Xgwm120 and EST-STS marker BE604758 at genetic distances of 2.9 and 5.5 cM, respectively. Since the flanking markers of MlLX99 were previously mapped to the bin 2BL2-0.36-0.50, MlLX99 must be located in this chromosomal region. MlLX99 showed a different resistance reaction pattern to 60 Bgt isolates from Pm6, Pm33, and PmJM22, which were all previously mapped on chromosome 2BL, but differed in their positions from MlLX99. Due to its unique position on chromosome 2BL, MlLX99 appears to be a new locus for resistance to powdery mildew. Liangxing 99 has shown superior yield performance and wide adaptation to different agricultural conditions, which has resulted in its extensive use as a wheat cultivar in China. The identification of resistance gene MlLX99 facilitates the use of this cultivar in the protection of wheat from damage caused by powdery mildew.
Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is one of the most important diseases that damages wheat (Triticum aestivum L.) production in China. Analysis of virulence structure and effectiveness of resistance genes is important in controlling powdery mildew with host resistance. This study was conducted to test virulence structures of 41 isolates collected from Shandong and Hebei provinces in 2011. The genetic diversity of these isolates was also analyzed using SSR markers. The virulence frequencies of isolates tested ranged from 0.35 (Bg40-2, Yantai, Shandong) to 0.74 (Bg46-1, Pingdu, Shandong). The mean virulence frequency for the isolates from Shandong Province was not significantly different from that of the isolates from Hebei Province. Except for a few resistance genes such as Pm17, the virulence frequencies of isolates from Shandong and Hebei provinces on most resistance genes were not different. None of the isolates tested was virulent on Pm24 carried by the Chi-1378 作 物 学 报 第 39 卷
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