世界上有许多这样的事例,在某个地区病原无意中被引进来了,而且定居下来,致使感病的寄主遭受灾难性损失。在植物自然社会中,病原和寄主趋向于通过淘汰感病性的个体和自然选择抗病的个体以达到生物平衡。然而,一种外来的病原,可以找到感病的寄主,而且在适宜环境条件下,可以引起 There are many such cases in the world that have inadvertently been introduced to a pathogen in a certain area and have settled down, causing catastrophic losses to susceptible hosts. In plant natural societies pathogens and hosts tend to achieve biological balance by eliminating susceptible individuals and naturally selecting resistant ones. However, an alien pathogen can find susceptible hosts and, under suitable environmental conditions, can cause