【作者】 王子迎；

【导师】 郑小波；

【作者基本信息】 南京农业大学 ， 植物病理学， 2006， 博士

【摘要】 大豆疫霉Phytophthora sojae是一种极为重要的植物病原菌，由其引起的大豆根腐病是大豆生产上的毁灭性病害之一。目前，利用大豆抗性是控制大豆疫霉根腐病最为经济有效的措施，但是，在实践中往往会出现新的毒性群体重新发展为优势群体而造成抗病品种失去作用的现象。研究大豆疫霉的群体遗传结构特征和致病性变化的分子机制，有助于揭示大豆疫霉的群体遗传结构变化的分子机理，从而有利于病害的控制。 就大豆疫霉的土壤诱捕方法进行了改进。改进措施主要是使用青霉素、利福平、五氯硝基苯和多菌灵等药剂(使用终浓度分别为50、20、25和25mg／L)控制诱捕大豆疫霉过程中的杂菌污染。采用改良的诱捕方法，从含有100个卵孢子的10g土样中诱捕到大豆疫霉菌的几率为100％。应用改良方法对采自中国黑龙江大豆田的土样和美国、巴西等进口大豆夹带的土样进行了大豆疫霉诱捕，结果显示，黑龙江土样的大豆疫霉的分离率为53％，而进口大豆夹带土样的大豆疫霉分离率为75％。 用SSR和RAPD两种分子标记对来自中国和美国的111个大豆疫霉菌株进行了DNA指纹分析。结果显示，20对SSR引物共扩增出113条条带，其中多态性条带比例为100％，而21条RAPD引物共扩增出223条条带，多态性条带比例为89％。SSR和RAPD分析都表明：在88％的相似性水平上可将111个菌株划分为7个遗传聚类组，且美国群体分布于更多的聚类组，显示更高的遗传变异度；中国福建的大豆疫霉群体与美国的大豆疫霉群体的遗传相似性最高，而福建群体与黑龙江群体的遗传相似性最低；此外，结果还发现，福建和黑龙江两群体的遗传多样性低于美国群体的遗传多样性。综合分析，美国的大豆疫霉不可能起源于中国黑龙江或福建；福建的大豆疫霉来自黑龙江的可能性较小，而来自美国的可能性更大；而黑龙江的部分大豆疫霉群体可能起源于美国，或者与美国大豆疫霉都起源于同一个起源中心。 采用在大豆植株上继代式连续接种大豆疫霉的方法研究了大豆疫霉与其寄主互作过程中毒力变化的现象。结果表明，大豆疫霉的毒力具有一定的可变性，但不同菌株毒力变异的能力存在差别；经过14代次的连续接种，得到了比出发菌株PS2的毒性明显增强的菌株PS2-vir。PS2-vir在卵孢子产量上明显低于PS2；毒力结构测定显示，PS2-vir与PS2的毒力公式都为1b，1d，2，3a，3b，4，5，6，7；RAPD分析表明，PS2-vir与PS2在DNA指纹上没有检测到差异。更多还原

【Abstract】 Phytophthora sojae is a major challenge to the production of soybean in the world. Plant resistance is currently the major control method for P. sojae root rot on soybean. However, resistant cultivars can promote the buildup of new virulent populations. Naturally virulent populations have been recovered from cultivated fields and natural areas; these infestations have resulted in the failure of resistant soybean cultivars. Therefore, genetic diversity in P. sojae population was studied to facilitate the soybean breeding for durable resistance and the disease integrated management. Moreover, studies on the pathogenicity mechanisms of oomycetes including P. sojae will help us to find special molecular targets of controlling the oomycete diseases.A simple and effective method to isolate P. sojae from soils was established. Penicillin, rifampicin, quintozene and carbendazim were used on the stages of oospore germination and zoospore baited by soybean leaf discs in the isolation of P. sojae from soil. These chemicals can most effectively eliminate Pythium and baterial contamination, and the pure isolates of P. sojae can be easily obtained. Under the control of chemical, the rate of baiting p. sojae from soils contained 100 oospores was 100%. Using this method, P. sojae was baited from soils collected from Heilongjiang province, soybeans imported from both Brazil and USA. The results showed that the rate of baiting p. sojae in soil samples from Heilongjiang province was 53%, and in soil samples collected from soybeans imported was 73%.The genetic diversity of three geographic populations of P. sojae from China and USA was determined using simple sequence repeats (SSRs) and random amplified polymorphic DNA (RAPD). Twenty pairs of SSR primers amplified 113 bands (alleles), of which all bands were polymorphic. Twenty-one of totally 200 random primers were selected were screened. A total of 223 reproducible RAPD fragments were scored among 111 individuals, of which 199 (89.23%) were polymorphic. Genetic similarity analysis based on SSR and RAPD fingerprints showed that the P. sojae populations of Fujian province and the United States were more similar to each other than to populations from Heilongjiang province. Cluster analysis with the unweighted pair group method revealed that the 111 isolates of P.更多还原