Genetic Polymorphism Differentiation From’Xanthomonas Axonopodis Pv. Citri’ In China

Citrus bacterial canker disease, caused by Xanthomonas axonopodis pv. citri, is one of the most destructive diseases and most important quarantine target on citrus industry in the world. Major quarantine are mainly focused on infect Rutaceae Citrus, Poncirus and other plants in domestic and abroad, the disease is mainly distributed in the main citrus producing areas in Asia, Africa and the Americas.Based on the difference among pathogenicity, host specialization and DNA hybridization homology, Xanthomonas axonopodis pv. citri could be categoried into five strains/three pathotypes:X. axonopodis pv. citri pathotype Ⅰ （strain A）, X. axonopodis pv. aurantifolia pathotype Ⅱ （strain B, C, D） and X. axonopodis pv. citrumelo pathotype Ⅲ （strain E）. The occurrence of Citrus canker in China’s Guangdong, Guangxi, Fujian, Jiangxi, Zhejiang, Hunan, Yunnan, Guizhou and other citrus-growing province （region） is more frequent in Sichuan, Hubei and other provinces that have a sporadical distribution.Assess the genetic diversity of the pathogen has become an important research direction pathogen, which not only facilitates the understanding of the genetic structure of populations and disease epidemiology law, but also provides a sensitive and specific method for the pathogen determination, disease diagnosis and risk management. This dissertation was maily funded by the National Public Service Sectors （agriculture） Research and Special （No.201003067-02） and Changjiang Scholars and Innovative Research Team （No. IRT0976）. In this thesis, different citrus canker strains from different geographic origins in China were genetically analyzed, a large number of polymorphic sites were chosed, amplified and evaluated. In this study, the followings are main results: In this study, X. axonopodis pv. citri str.306lines （NC₀03919.1） was chosed, from which18tandem repeat loci were selected to design appropriate primers for PCR amplification, the experimental results showed that the different strains of between the number of points exhibited significant polymorphism. In this study18tandem repeat loci primers while6primers did not.12pairs of primers can simultaneously amplify and laboratory strains Jiangxi samples, with four pairs of amplified target marketing repeat primer sites of amplification products showed significant differences in polymorphic bands by agarose gel electrophoresis with EB imaging. The samples were colletcted from Jiangxi provinces in southeastern China, save sample collection and laboratory collected before the Chongqing region, the two regions relative geographical isolation, a significant difference from the agarose gel electrophoresis analysis of samples with type PCR from four sites amplification Analytical brought with such sites may be present sequence deletions or insertions. These results suggested that differences between the sites in the differentiation of the population may be very valuable as sites of differentiation of populations and polymorphism analysis for further analysis and evaluation.This study samples collected from Guizhou, Hunan, Guangxi, Zhejiang and other provinces citrus canker four suspected samples, samples collected using primers for PCR analysis of xac01/xac02,collected162samples were positive samples. The results showed that the acquisition of citrus canker pathogen strains can detect the target gene. In this study tandem repeat loci amplified samples collected target gene loci differences fragments. Hunan, Zhejiang, Guizhou, Guangxi, Jiangxi detection rates exist some differences between them, the detection rate of change in the three regions overall trend is decreasing （from100%to90.1%）. Repeat the number of repeating units appear in different provinces vary in all strains of the same province, the difference between the strains is not too large, the general difference is therefore presumed to be sequenced more strains may also find other big difference TRNs strains. It is suggested that the mechanism of different strains TRNs through successive changes tend to be more repeating units produced.Through the sample sequence alignment sequence analysis using molecular evolutionary genetic analysis software MEGA phylogenetic analysis, phylogenetic analysis using UPGMA construct phylogenetic trees, each samples province roughly classified as a family, a big difference sample northwest Hunan and Guangxi, Guizhou, Jiangxi and Zhejiang, guess the reason but due to geopolitical factors, northwest Hunan and Chongqing, Hubei, bordering mostly mountainous, therefore, the sample may formation of a specific geographic specifically resistance. From the analysis of the evolutionary tree populations citrus canker pathogen, Guizhou and Jiangxi province differentiate differences are more obvious. In this paper, differential expression was conducted to analyze the potential polymorphic loci in samples infected citrus canker. Citrus canker pathogens were treated at28℃/200mM CuSO4·5H2O with Oh,1h,2h,3h,4h and5h, and ultraviolet light treatment of0min,15min,30min,45min and60min, respectively. Expression levels of XAC0922, XAC1380, XAC1682, XAC2191, XAC3788, XAC3824, XAC1319, XAC1933, XAC3989and XAC4912and other10genes were measured. Results showed XAC4912turened out a most dramatic changes in the gene polymorphisms, which had a potential utility to study the license citrus canker bacteria.