欧美杨细菌性溃疡型烂皮病病组织微生物多样性及其协同致病机制研究

A new disease of poplar trees (Populus×euramericana) showing serious bark cankers with copious exudations was first oberved in China in 2005. And no related reports obout the disease were found in all the world. The disease extended at a very fast speed, and the large area of rotten bark would be oberved within 2-3 weeks from the very beginning. What is mechanism the pathogen? Are there other pathogenic microbiology? To understanding key issues, two studies will be carried out in present project. .1) Micorbial diversity of barker canker tissues, including micorbial diversity of different parts of canker tissues and fluctuations of microbial diversity of the tissue after inoculation of pathogen, will be performed by the integration of 16S rRNA and 18S rRNA gene libary - and culture-based approaches. And, the unpublished bacterial species will be classified. .2) The potential roles of the micorbiology in the canker tissue and their pathogenesis will be analyzed by the integration of metagenomics- and inoculation-based approaches with the poplar trees. The present research will ascertain how many species are potential pathogen, and what are their collaborative roles. And the results of this study will contribute the research about disease contol and ocurrence of disease.

2005年，我国欧美杨上发现一种新的危害非常严重的溃疡病，国内外均无相关报道，为区别于传统的杨树溃疡病，现将其命名为欧美杨细菌性溃疡型烂皮病。该病害不仅病斑扩展速度快，且2-3周内能导致树皮的大面积腐烂，其如何致病？机制是什么？是否存在多种协同致病菌？为回答上述问题，本项目将开展以下两方面的研究：.1)利用分离鉴定和现代分子生物学技术（基因文库分析）相结合的方法分析病组织中微生物多样性状况,包括以下3项研究内容：①病组织不同部位的微生物多样性分析；②接种病原细菌的植株病组织中微生物多样性随时间的动态变化分析；③可培养未知种细菌的分类鉴定。.2)利用接种和宏基因组学方法开展病组织中各类微生物的作用及其协同致病机制研究。.本研究旨在弄清欧美杨细菌性溃疡型烂皮病病组织中协同致病菌的种类及其在致病作用，探明其致病机制，为该病害防治方法和针对性地防治对策的制定奠定基础。

染病组织微生物物种多样性丰富，27个病斑样品中共测得370个细菌out，210个真菌out，说明该环境微生物种类繁多。利用传统的分类培养的方法获得细菌500余株，属于130余种，发现潜在细菌新物种20余种，已发表命名新属种12个，其中包括新属5个。分离方法和高通量测序方法分析结果一致，不同部位优势种群存在明显差异，病健交界处优势种群为Lonsdalea populi、Lactobacilus等，腐烂部位绝对优势种群则变为发酵相关微生物（如Lactobacilus）和真菌为镰刀菌（Fusarium solani），L. populi数量有所下降。通过接种和高通量测序的方法明确了病斑中微生物的随时间演替规律，病原菌L. populi从非优势变为优势、绝对优势、变非优势的过程。根据宏基因组结果发现病斑微系统中优势菌群具有协同致病的能力，特别是镰刀菌能明显的加重病害危害程度。这些微生具有果胶降解酶、纤维素降解酶、木栓和蜡质降解相关功能，它们通过降解病斑的微环境中的纤维素、果胶和木栓加重病害的危害程度。