空间和气候对桉树斑点溃疡病原T. zuluensis遗传多样性和繁殖方式影响的研究

Eucalypt plantations make up 5.8% of the whole plantation area of China, while 20% of timber is obtained from eucalypt trees in this country. Eucalypt Teratosphaeria stem spot canker is one of the most serious diseases of eucalypt trees in 12 countries and regions in the world. In China, ten percent of eucalypt plantations were threatened by this canker disease caused by Teratosphaeria zuluensis. Previous studies had shown the population genetic diversity in China was the highest for the population from eucalypt plantations in several countries in the world, and sexual reproduction was only presented in the population from eucalypt plantations in China. In this project, the gene diversities, genotype diversities and population structures of twelve T. zuluensis populations collected from twelve regions in five Provinces, which represent five different climate types in southern China will be determined by using microsatellite markers. This research can help to elucidate the genetic mechanisms about spatial and climatic factors on influencing the genetic diversity, reproduction, recombination mode of T. zuluensis. Furthermore, this project also can provide a theoretical basis on reveal the potentially original region and spatial genetic structure of T. zuluensis, these research results will provide important information on controlling the spread of the pathogen, and provide a foundation for management of disease caused by T. zuluensis on eucalypt plantations in different spatial regions and different climate types in China.

桉树占全国人工林面积的5.8%，提供了20%的木材产量。桉树Teratosphaeria斑点溃疡病严重危害着世界十二个国家和地区的桉树人工林，由T. zuluensis引起的该病害威胁着我国桉树人工林10%的种植区域。本课题组前期研究表明世界范围内我国T. zuluensis种群的遗传多样性最高，且唯一存在有性重组现象。本项目拟采用微卫星探针对华南五省份-十二地区，分布于五个气候亚类的十二个T. zuluensis种群进行扩增，来分析和阐明T. zuluensis不同种群的基因多样性、基因型多样性和种群结构。本项目将为揭示T. zuluensis的潜在起源地，为阐明空间和气候因素对T. zuluensis遗传多样性、繁殖方式、遗传重组模式的影响机制提供思路。此外，本项目对控制T. zuluensis的传播、建立适地适气候类型的有针对性的T. zuluensis病害防控策略具有重要指导意义。

由Teratosphaeria zuluensis病原真菌引起的桉树斑点溃疡病是危害我国南方地区桉树人工林健康的重要病害之一。本项目对华南地区12个地区18个采样地点的桉树斑点溃疡病进行了系统的病害调查和样品采集。对引起桉树斑点溃疡病的病原菌、伴生菌以及桉树人工林中与桉树亲缘关系相近存在病原菌寄主转移的其他桃金娘科植物的溃疡病原菌进行分离。对分离到的病原菌根据分子系统发育分析，鉴定了病原菌的种类，并进行了致病性测试。采用ITS序列，针对10个区域，选择各个区域内包含所有基因型的代表性菌株，与世界范围内各个国家（或地区）T. zuluensis的所有ITS基因型序列进行比对，并进行系统发育分析，阐明了我国T. zuluensis菌株的多样性以及在世界范围内的进化地位。随后对引起桉树斑点溃疡病的T. zuluensis病原菌根据其分离地域的地理位置和气候差异分为10个种群，采用9对多态性微卫星引物对10个种群的485株T. zuluensis菌株进行扩增并对扩增产物进行基因扫描，进而进行种群分析。分析结果表明我国所有T. zuluensis种群的基因多样性较高，不同种群之间基因多样性差异不大；大多数种群的基因型多样性较高，大多种群之间基因型多样性差异不大；我国T. zuluensis种群间的遗传差异比较小，种群内的遗传变异比种群间的要大；分布于气温较低的亚热带中部和北部的部分种群存在遗传重组。本项目研究结果表明空间和气候因素对T. zuluensis的遗传多样性影响不大，气候因素对T. zuluensis的繁殖方式影响较大。本项目的研究结果对阐明我国桉树斑点溃疡病流行的成因具有一定的意义。