中国热带、亚热带森林生态系统中疫霉菌的分类及分子系统学研究

Phytophthora species are important plant pathogens with world-wide distribution, and the vast majority of them are notorious pathogens. With the increased attention given to the genus Phytophthora in the last decade in response to the ecological and economic impact of several invasive species (such as P. ramorum, P. kernoviae, and P. alni), there has been a significant increase in the number of described species. In the last decade, about 20 new Phytophthora species or taxa were recovered from forests and natural ecosystems. In China, there are currently 28 described species of Phytophthora, most of which are pathogens of agricultural crops or ornamental plants. So far there are few reports of Phytophthora diseases of trees or of Phytophthora surveys in the forests in China, and the species or molecular systematics are unknown to all. Therefore, the objectives of this study were to isolate and identify Phytophthora species by baiting techniques from canopy-drip,streams, soil and trees in tropical and subtropical forests by ITS rDNA sequences and morphological features, to know the hosts, pathogenicity and phylogeny of these species, to predict the potential geographic distribution, to analyze the risk and their ecological roles in forest ecosystem , and to evaluate the genetic diversity of Phytophthora populations using a combination of morphological and molecular tools. These Phytophthoras will be classified into known species or new species in the ITS clades or subclades,and the origin and hosts of these pathogens will be clear. The results of this study will contribute the research about contol and ocurrence of Phytophthora disease.

疫霉菌（Phytophthora de Bary）是一类重世界性分布的重要植物病原菌，其绝大多数种类对寄主植物具有严重的危害性和破坏性。但迄今为止，我国对由疫霉菌引起的林木病害的研究报道很少，缺乏对森林疫霉病菌种类、分布、寄主范围的调查，更缺少对森林疫霉分类及其系统发育的研究。本研究利用多种调查监测方法，通过ITS、Cox I、β-tubulin等多个基因序列分析和SRAP分子标记技术，结合选择性分离培养、形态观察、致病性测定等常规方法对在我国热带、亚热带森林中的疫霉菌进行系统调查和鉴定，摸清其中的疫霉菌种类，掌握其致病性、寄主范围、潜在分布区和风险性，分析其系统发育关系及与国外已报道疫霉菌之间的亲缘关系，探讨重要种群在森林中的时空分布格局和其遗传多样性。该研究不仅对我国森林疫霉菌的科学分类研究和外来疫霉菌的防控具有推动作用，还将为我国森林疫病的防治提供科学依据。

项目对我国海南、云南、四川等9个省区森林生态系统中的疫霉菌进行了采样和调查，累计采集疑似疫霉危害症状的植物材料888份、土壤样品1347份、溪流监测样品2347份和林冠穿透水监测样品1145份；利用选择性培养基，通过实验室内常规植物组织分离法，从采集或诱捕收集的植物样品上，总共分离获得了2256株疫霉菌的纯菌株，并用CMA培养基对其进行了保存；通过形态学特征观察和rDNA ITS等序列分析相结合的方法，对项目所收集的疫霉菌株进行了鉴定，初步摸清了我国热带、亚热森林生态系统中疫霉菌的种类有27种，其中包括我国已有记录种12个，新纪录种9个，另外还发现了归属于ITS Clade 2、6和9中的疫霉新种6个；发现了栎树疫霉猝死病菌（Phytophthora ramorum），并对其致病性、国内寄主范围进行了初步研究，分析了其与欧美菌株之间的系统发育关系及亲缘关系；另外，本项目还初步建立了中国森林疫霉菌数据库和构建完成了重要森林疫霉菌多寄主疫霉（P. plurivora）的SARP分析体系，探讨其种群在森林中的时空分布格局和其遗传多样性与致病性、寄主、地理来源等因素之间的关系，进一步揭示了我国热带、亚热带森林中疫霉菌的多样性，推动了我国森林疫霉菌的科学分类研究，为我国森林疫病的防治和检疫提供了科学依据。