Abstract:

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.

Key words: Wheat (Triticum aestivum), Powdery mildew(Erysiphe graminis f. sp. tritici), Resistance genes, SSR, Gene location