Among the emerging fungal diseases threatening food security, the Pseudocercospora fijiensis fungus causing black leaf streak disease of banana is one of the most marked examples of a recent worldwide pandemic on a major crop. We assessed how this pathogen spread throughout the latest invaded region, i.e. Central America and the Caribbean. We retraced its population history combining detailed monitoring information on disease outbreaks and population genetic analyses based on large-scale sampling of P. fijiensis isolates from 121 locations throughout the region. The results first suggested that sexual reproduction was not lost during the P. fijiensis expansion, even in the insular Caribbean context, and a high level of genotypic diversity was maintained in all the populations studied. The population genetic structure of P. fijiensis and historical data showed that two disease waves swept northward and southward in all banana-producing countries in the study area from an initial entry point in Honduras, probably mainly through gradual stepwise spore dispersal. Serial founder events accompanying the northern and southern waves led to the establishment of two different genetic groups. A different population structure was detected on the latest invaded islands (Martinique, Dominica and Guadeloupe), revealing multiple introductions and admixture events that may have been partly due to human activities. The results of this study highlight the need to step up surveillance to limit the spread of other known emerging diseases of banana spread mainly by humans, but also to curb gene flow between established pathogen populations which could increase their evolutionary potential.

在威胁粮食安全的新出现的真菌病害中，引起香蕉黑叶条病的斐济假尾蚴真菌是近期全球主要作物流行病的最显着例子之一。我们评估了这种病原体如何在最近入侵的地区，即中美洲和加勒比地区传播。我们根据对整个地区 121 个地点的斐济假单胞菌分离株的大规模采样，结合疾病爆发的详细监测信息和种群遗传分析，追溯了其种群历史。结果首先表明，在斐济对虾期间并没有丧失有性生殖扩张，即使在加勒比海地区，并且在所有研究的人群中都保持了高水平的基因型多样性。斐济对虾种群遗传结构历史数据显示，研究区所有香蕉生产国的两次疾病波从洪都拉斯的初始进入点向北和向南席卷，可能主要是通过逐渐逐步的孢子传播。伴随着南北浪潮的连续创始人事件导致了两个不同的遗传群体的建立。在最近被入侵的岛屿（马提尼克岛、多米尼加岛和瓜德罗普岛）上发现了不同的种群结构，揭示了可能部分是由于人类活动造成的多次引入和混合事件。这项研究的结果强调了加强监测的必要性，以限制主要由人类传播的其他已知的香蕉新发疾病的传播，同时也需要遏制已建立的病原体种群之间的基因流动，这可能会增加它们的进化潜力。