| Wheat powdery mildew and stripe rust, caused by Blumeria graminis f.sp.tritici (syn. Erysiphe graminis f.sp.tritici) and Puccinia striiformis Westend, respectively, are two damaging and strongly epidemic diseases of wheat occuring around the world. It is a complexity and long work to control these diseases. As the new virulence pathogen occurred, many resistant varieties were lost their resistance to the two diseases. Screening and identification of new resistance are of major importance in breeding for an efficient genetic control strategy. In this study, the genetics of the resistance genes in a new wheat line 101-3 which were immune to both predominant powdery mildew and stripe rust in southwest of China were carried out. 101-3, a stable wheat line, was derived from the progenies of wild cross between wheat and a hexaploid amphiploid of T.durum-Dasypyrum. The result through in situ hybridization indicated that there not were any chromosomal changes in 101-3, suggesting that the resistance genes for powdery mildew and stripe rust in this line might produced by mutation or small fragment translocation between alien chromosome fragment and wheat chromosomes. The main results were list follows:1. The wheat line 101-3 was immune to powdery mildew and stripe rust which were predominant in the field of southwest, China.2. No visible symptoms for powdery mildew and stripe rust were found in the two F1 hybrid plants of 101-3×MY11 and SY95-71×101-3 while the parents of MY11 and SY95-71 were highly susceptible for both diseases. The two F2 populations were segregated resistant and susceptible and showed a good fit of 3:1 ratios for powdery mildew and stripe rust respectively. These results showed that the resistances for wheat powdery mildew and stripe rust might be controlled by a different single dominant gene.3. F2 progenies from the crosses of Chinese spring monosomic lines with the wheat line 101-3 showed a ratio of 3:1 resistant to susceptible in 19 cross-combinations when inoculated with mixed powdery mildew races except the monosomic 6B as one of parents. The segregation of F2 plants from the cross of monosomic 6B with 101-3, however, deviated significantly from the 3:1 ratio with 94 resistant to 7 susceptible plants. This verified that the wheat line 101-3 possessed a single dominant gene conferring the resistance of powdery mildew and the resistance gene of powdery mildew was located on chromosome 6B.4. The segregation results of resistance and susceptible for wheat stripe rust in F2 progenies from the crosses of 21 Chinese Spring monosomic with line 101-3 using mixed stripe rust races of CYR31 and CYR32 infection indicated that the ratio between resistance and susceptible plants deviated significantly from 3:1 only with monosomic 1B, while the other combinations showed a good fit for 3:1 ratios, which suggested that the single dominant resistance gene for wheat stripe rust in line 101-3 was on chromosome 1B.5. The two resistant genes in line 101-3 was immune to the widespread predominant epidemic races of stripe rust and powdery mildew and has different origin as known genes on chromosome 1B for stripe rust and 6B for powdery mildew, respectively. These results showed that the two genes are both new genes. However, it is uncertain whether the two genes are allelic or lined with other resistance genes located on Chromosome 6B for powdery mildew and 1B for stripe rust. Further allelism tests are necessary to determine the relationships between the resistance gene and other genes located on chromosome 6B for powdery mildew and 1B for stripe rust through molecular markers. |
