Dissertation
Dissertation > Agricultural Sciences > Plant Protection > Pest and Disease Control > Crop pests and diseases and their prevention > Cereal crop pests and diseases > Wheat pests and diseases > Disease > Transgression ( pass ) an infectious agent harmful

Population Genetic Diversity Analysis of Puccinia Triticina in Some Regions of China Based on SSR

Author XuMinQing
Tutor MengQingFang; LiuDaQun
School Agricultural University of Hebei
Course Plant Pathology
Keywords Puccinia triticina SSR marker Virulence Genetic diversity Genentic recombination
CLC S435.121.4
Type Master's thesis
Year 2012
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Wheat leaf rust caused by Puccinia triticina is one important epidemic disease that occurs regularly where the wheat is grown, and also is a major disease of wheat in China. Studying the population genetic structure of P. triticina is benefit for understanding the genetic variability of P. triticina populations, and it is also very important for the deployment of resistant cultivars.In the research, all the Chinese P. triticina samples collected from Hebei, Henan, Shandong and Sichuan provinces in 2009 were analyzed by SSR marker to understand the molecular genetic diversity. The main results were as follows:1. Single uredinial isolates (120 in total) were isolated from the collections and tested for virulence phenotype on near-isogenic lines with known leaf rust (Lr) resistance genes and other lines with known Lr genes. Dendrogram analysis showed that there was high virulence similarity among regions, and similarity coefficients were 0.74-1.00, indicating that there were little differences on virulence genes contained in P. triticina. The isolates from different regions had the same virulence phenotype.2. One hundred and twenty single uredinial isolates were analyzed with 30 simple sequence repeat (SSR) markers, 25 of them could produce steady and clear polymorphic bands. Eighty-five DNA fragments were produced by 25 SSR primers among 120 isolates, including 64 polymorphic fragments, accounting for 75.29% of the total fragments. The number of alleles per locus ranged from 2 to 8, with an average of 3.4 alleles/locus. Dendrogram analysis showed that genetic similarity coefficients were 0.74-1.00, SSR genetic polymorphisms had some correlation with isolates origin. The isolates from different regions had the same genotype, which demonstrated the gene flow among the regions.3. Dendrogram of virulence was compared with the dendrogram of SSR, indicating no relationship between them was found. The MXCOMP module in NTSYS-pc2.10e was used to analyze the relationship between virulence and SSR marker. The result showed that the coefficient was 0.04. 4. The six virulence phenotypes with high frequency including 59 isolates were analyzed for their molecular polymorphisms and virulence polymorphisms. Virulence phenotypes had high level of genetic diversity. Virulence phenotypes had no relationship with SSR genotypes. Different virulence and different genotypes might be present in the same pathotype. The same or near genotypes might be present in the different pathotypes.5. Genetic analysis was conducted by POPGENE version1.32 based on SSR datas. The result showed that the populations of P. triticina were considerably genetic diversified and the genetic diversity level of P. triticina in Hebei, Henan, Shandong were higher than that in Sichuan. UPGMA cluster analysis showed that 4 populations were clustered into 2 groups at similarity coefficient 0.96, Henan, Shandong and Sichuan clustered in group 2, Hebei clustered in group 1, and the closest genetic relationships were found between Henan and Shandong, indicating that there was high genetic similarity among regions, and the genetic relationships were associated with graphical distribution. Genetic differentiation was investigated by AMOVA, the results showed that there were about 8.93% of the total variations among populations and about 91.07% of the total variations within populations. The main genetic variation came from the same population. The Nm was 6.10, indicating that migration of pathogen among the regions was presented.6. Primer RB8 could detect the recombinant among the P. triticina populations. The percent of recombinant was 82.5%, which were different among regions. This study revealed genetic recombination by SSR markers.

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