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Identification and Molecular Mapping of New Powdery Mildew Resistance Genes in Common Wheat

Author: MaHongQi
Tutor: MaZhengQiang
School: Nanjing Agricultural College
Course: Biochemistry and Molecular Biology
Keywords: Common wheat powdery mildew-resistance gene molecular mapping PmD57-5D PmD57-6D PmD29
CLC: S512.1
Type: Master's thesis
Year: 2010
Downloads: 10
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Abstract


Powdery mildew, caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici (Bgt), is a serious foliar disease of wheat (Triticum aestivum L.) worldwide. Utilization of disease-resistant cultivars is the most efficient and environmentally friendly approach to control this disease. Strategy for breeding powdery mildew-resistant wheat mainly employs race-specific resistance genes, which could be overcome in a short period of time when being extensively used due to the co-evolution of pathogen virulence and host resistance. Thus, a long-term objective for wheat geneticists and breeders is to identify and utilize new powdery resistance genes.Common wheat germplasms D57 and D29 showed a high level of resistance to powdery mildew. In this study, we studied the inheritance of their resistance, mapped the resitance genes and evaluated the resistance genes’spectra.Genetic analysis performed with the F2 population and F2:3 families derived from cross Yangmail58×D57 showed that D57 contains two dominant resistance genes evaluated with powdery mildew isolates Bgt18 and Bgt19. The segregated F3 families responsed by a single restance gene were selected and used as the mapping populations, and the two genes were mapped seperately with molecular markers. The first gene was located on chromosome 5DS, and was temperately named PmD57-5D, which was flanked by Xgwm205 and Xmag6137 with genetic distance of 8.3 cM and 2.8 cM, respectively. The second one was located on 6DS, and was designated as PmD57-6D. This gene was flanked by Xmag6139 and Xmag6140 with genetic distance of 0.7 cM and 2.7 cM, respectively. In addition, the RFLP probe BCD 1871 and ESTs BE498794, BG262421 and BE445201 were converted to STS markers, and the first two were linked with PmD57-5D, the last two were linked with PmD57-6D. PmD57-5D was in close proximity to Pm2, and there was no difference of resistance spectrum to 15 powdery mildew isolates between them. PmD57-6D was a new powdery mildew resistance gene, which has not been reported up to now. F2 and F2:3 populations were also constructed from cross Yangmai158 and D29. Genetic analysis showed that D29 contains a dominant powdery mildew resistance gene, which was temperately designated as PmD29. Two STS markers Xsts_bed1231 and Xp9-7 were co-segregated with PmD29, and four SSR markers Xhbg327, Xgdm93, Xgwm526 and Xgwm356 were closely linked with it. The location of PmD29 was similar to Pm4, and allelism test was confirmed that PmD29 and Pm4a were allelic each other. However, the resistance spectrum of PmD29 was distinctly different fom Pm4a, Pm4b and Pm4c. Therefore, PmD29 should be a new resistance allele of Pm4.

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