Phytopathology. 2014 Feb;104(2):120-5. doi: 10.1094/PHYTO-06-13-0154-R.
The ecology of plant pathogens of perennial crops is affected by the long-lived nature of their immobile hosts. In addition, changes to the genetic structure of pathogen populations may affect disease epidemiology and management practices; examples include local adaptation of more fit genotypes or introduction of novel genotypes from geographically distant areas via human movement of infected plant material or insect vectors. We studied the genetic structure of Xylella fastidiosa populations causing disease in sweet orange plants in Brazil at multiple scales using fast-evolving molecular markers (simple-sequence DNA repeats). Results show that populations of X. fastidiosa were regionally isolated, and that isolation was maintained for populations analyzed a decade apart from each other. However, despite such geographic isolation, local populations present in year 2000 were largely replaced by novel genotypes in 2009 but not as a result of migration. At a smaller spatial scale (individual trees), results suggest that isolates within plants originated from a shared common ancestor. In summary, new insights on the ecology of this economically important plant pathogen were obtained by sampling populations at different spatial scales and two different time points.
多年生作物病原物的生态学受到其不活动宿主长寿命的影响。此外，病原种群遗传结构的变化可能会影响疾病的流行病学和管理实践；例如，更适合的基因型的局部适应，或通过受感染植物材料或昆虫媒介的人类活动从地理上遥远的地区引入新的基因型。我们使用快速进化的分子标记（简单序列 DNA 重复），在多个尺度上研究了导致巴西甜橙植物发病的韧皮部坏死病菌种群的遗传结构。结果表明，韧皮部坏死病菌种群在区域上是隔离的，而且相互之间相隔十年的种群也保持着隔离。然而，尽管存在这种地理隔离，但 2000 年出现的当地种群在 2009 年已基本被新基因型所取代，而这并非迁徙的结果。在较小的空间尺度（单棵树）上，结果表明，植物内的分离株源自一个共同的祖先。总的来说，通过在不同的空间尺度和两个不同的时间点对种群进行采样，我们对这种具有重要经济意义的植物病原物的生态学获得了新的认识。
