油茶炭疽病是我国油茶产区的一种重大病害，造成严重经济损失。我们前期的研究发现：①油茶炭疽病由多种炭疽属真菌引起，并且这些炭疽属真菌种内存在重组、种间存在杂交现象；②海南五指山的油茶（油茶苗购于江西长埠）炭疽病菌具有独特的基因型，但与江西长埠或中国内陆其它油茶炭疽病菌共享部分等位基因。我们据此提出一种假说：当地植物（包括当地油茶）炭疽病菌转移到油茶树上，或当地植物炭疽病菌与油茶炭疽病菌之间存在重组或杂交。目前，除了已知油茶组织中潜伏的炭疽病菌能再次引起病害发生外，其它寄主植物的炭疽病菌是否也可以侵染油茶，以及这些病菌之间的遗传关系尚不清楚。为了证明提出的假说，本项目采用多基因序列分析和微卫星标记方法，研究我国油茶及其它寄主植物炭疽病菌群体内和群体间以及种内和种间的基因交流和遗传变异规律，探明油茶炭疽病菌潜在侵染源植物种类，揭示此类病菌的分子进化机制，为可持续控制油茶炭疽病提供理论依据。

Anthracnose is a major disease of tea-oil trees in China, causing enormous economic losses. The major casual agents are species in the fungal genus Colletotrichum. Our recent preliminary results based on sequences at four gene fragments indicated that at least five species in this genus could cause anthracnose on tea-oil trees. In addition, new and undescribed species may exist and there is phylogenetic evidence for hybridization between some of the species. At present, the relative virulence of these species and their hybrids on tea-oil trees are unknown. In addition, the potential sources of strains causing anthracnose on tea-oil trees remain to be defined. One potential source is other host plants in nearby fields. Understanding the potential sources of infection and the virulence properties of these pathogens will significantly enhance our ability to design sustainable control strategies against anthracnose on tea-oil trees. Here we propose to sample strains of Colletotrichum from both tea-oil trees and other host plants in nearby fields and forests, obtain their genotypes using multiple gene sequences and microsatellite markers, and conduct cross-infection experiments using representative tea-oil tree cultivars and fungal pathogen species/genotypes. Our analyses will identify genetic variation within and among populations, the intraspecific and interspecific relationships among Colletotrichum species between tea-oil trees and other host plants, and their relative specificity in host-pathogen interactions. The research results will provide the theoretical foundation for developing sustainable methods to control anthracnose in tea-oil trees. The approaches and methods developed here can also help guide our managements of other plant infectious diseases.