Isolation And Characterization Of Wheat Powdery Mildew Resistance Gene Homology Sequence And Study On Molecular Marker

Powdery mildew caused by Erysiphe graminis DC is a severe wheat disease in China, which has become more and more serious recently. Breeding resistant cultivars has been proved the most effective way to control this disease; however, the comprehensive understanding of disease resistance genes is the premise. Up to now, 28 loci with 45 main effective genes were identified in wheat. They were located in different chromosomes respectively. Corresponding for some of them markers had already been found, but none of the resistance genes of wheat has successfully been cloned so far. In this study, NILs of different resistance genes, such as Pm2, Pm4b and PmJ6, were used for cDNA synthesis. RT-PCR was performed by using cDNA from these NILs as template, in addition, the primers were designed based on the conserved domains of disease resistance genes already known. Furthermore, chromosomal localization and gene expression analyses were finished with some interesting cDNA clones. On the other hand, according to the SSR-marker linkage map, screening for SSR markers closely linked to the resistance genes was carried out using the relative NILs with Pm2, Pm4b, Pm21 and an unknown resistance gene for powdery mildew as plant materials. The followings were concluded: 1) Mo, Mia and NBS-LRR like expressive gene sequences were isolated from wheat genome. Their GenBank accession numbers are AY084049, AF499035 and AY084050 respectively. Ten single nucleotide polymorphism (SNPs) between the R and S were found within the NBS-LRR. Fragment patterns was differentiated between the R and S plants with the primer pair based on the SNP158. Between control harvested just before inoculation and the material of PIH (post-inoculation hour) 72 using E. Graminis as pathogen, the obvious difference in mRNA splicing of this gene is observed, implying this gene may be involved in disease resistance of wheat. Using nulli-tetrasomic lines of "Chinese Spring", the NBS-LRR like gene is located on ID chromosome of wheat. 2) A NBS-like gene, which is in the forms of genomic DNA clone and cDNA clone, was isolated from wheat genome. It showed 99% homology to the Cre3 gene. However, there was no difference found between the R and S plants. Whether this fragment is related tothe disease resistance of wheat or not should be further testified. 3) One candidate gene sequence of ADP-ribosylation factor was isolated from wheat genome using primer pair of RPW81C. It showed 92% homology to the ADP-ribosylation factor gene from rice and 86% homology to the ADP-ribosylation factor gene from wheat. 4) Fifty pairs of SSR primers, which are located on 5DS, 2AL, 6A and 4D respectively, were screened. It is found those two pairs of primers: WMC201 and Xgwm570, on 6AL of wheat were suitable for differentiating the R and S pools. The linkage distance is 27.1cM between the WMC201 and the Pm21gene using (R43/5*Bainong3217) NIL F, segregated population.