YU25是从八倍体小偃麦TAI7047与小麦栽培品种川麦107杂交后代中选育出的对白粉病免疫的小麦育种新材料。以感白粉病小麦品种MY11与YU25杂交和回交的后代F1、F2、BC1F1和BC2F1为材料，采用四川省当前流行的小麦白粉病优势生理小种人工接种，对YU25的白粉病抗性进行了遗传分析。结果表明，YU25含有2对表现免疫反应和高抗反应的显性抗病基因，暂命名为PmE(免疫)和PmYU25(高抗)。用294对小麦微卫星引物和221个F2植株，对这2个基因进行连锁分析，发现小麦微卫星标记Xgwm-297-7B与PmE基因的遗传距离为13.0 cM，而Xgwm-210-2D与PmYU25基因的遗传距离为16.6 cM，因此将PmE和PmYU25分别定位在7BS和2DL上。根据系谱和基因位点分析，推断PmE和PmYU25均为起源于中间偃麦草、不同于已知的抗小麦白粉病基因的2个新基因。小麦育种新材料YU25含有可能来源于小麦-中间偃麦草的染色体多重易位，其细胞学基础和在实际育种中的应用值得进一步研究。
Powdery mildew, caused by Erysiphe graminis f. sp. tritici, is a major wheat (Triticum aestivum L. em Thell) disease in the world. The use of resistant cultivars is the most economical, effective and environmentally safe way to control this disease. A new wheat line YU25, which derived from a wide cross between a wheat cultivar CM107 and octoploid Trititrigia TAI7047 (Taiyuan 768/ Elytrigia intermedium//76(64)), exhibit immune to wheat powdery mildew. In the present study, for genetic analysis of its resistance to powdery mildew, the line YU25 was crossed with a susceptive wheat cultivar Mianyang 11 (MY11) and backcrossed both with MY11 and YU25 to produce their F1 (25 individuals), F2 (352 individuals), BC1F1 (55 individuals) and BC2F1 (80 individuals) populations, which were grown in greenhouse and inoculated by the epidemic predominant race of powdery mildew in Southwest China. The response patterns of F2 population showed that the I (immune):R (resistant):S (susceptible) segregation ratio closely fit to 12:3:1, suggesting that the wheat line YU25 carried two different dominant resistance genes to powdery mildew, one of them exhibited immune and the other showed highly resistant. The results was also supported by the 2:1:1 segregation ratio of I:R:S in the BC1F1 population. F2 population consisting of 221 individuals was screened with 294 wheat microsatellite primer pairs to detect molecular markers linked to genes responsible for powdery mildew resistance. The results indicated that the microsatellite marker Xgwm297-7B on chromosomal arm 7BS and Xgwm210-2D on chromosomal arm 2DL were linked with the immune gene and highly resistant gene to wheat powdery mildew, with the genetic distance 13.0 cM and 16.6 cM, respectively. So far, there is no reported resistant gene to powdery mildew on chromosome arm both 7BS and 2DL. Moreover, there are also no genes conferring resistance to wheat powdery mildew with the origin of E. intermedium. Hence, pedigree analysis of YU25 and chromosomal location of the genes afforded a persuasive evidence to support the conclusion that the immune gene and highly resistant gene in YU25 derived from E. intermedium, are new genes for resistance to powdery mildew in wheat and are temporarily designated PmE and PmYU25, respectively. It could play an important role in wheat breeding programs for powdery mildew resistance. The application value of the line YU25 in wheat breeding, which should contain double translocation between wheat and E. intermedium chromosomes, was discussed in this paper.
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