Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Blacksburg, VA, USA.
New Phytol. 2013 Aug;199(3):800-11. doi: 10.1111/nph.12316. Epub 2013 May 21.
While the existence of environmental reservoirs of human pathogens is well established, less is known about the role of nonagricultural environments in emergence, evolution, and spread of crop pathogens. Here, we analyzed phylogeny, virulence genes, host range, and aggressiveness of Pseudomonas syringae strains closely related to the tomato pathogen P. syringae pv. tomato (Pto), including strains isolated from snowpack and streams. The population of Pto relatives in nonagricultural environments was estimated to be large and its diversity to be higher than that of the population of Pto and its relatives on crops. Ancestors of environmental strains, Pto, and other genetically monomorphic crop pathogens were inferred to have frequently recombined, suggesting an epidemic population structure for P. syringae. Some environmental strains have repertoires of type III-secreted effectors very similar to Pto, are almost as aggressive on tomato as Pto, but have a wider host range than typical Pto strains. We conclude that crop pathogens may have evolved through a small number of evolutionary events from a population of less aggressive ancestors with a wider host range present in nonagricultural environments.
虽然人类病原体的环境储库的存在已得到充分证实，但对于非农业环境在作物病原体的出现、进化和传播中的作用知之甚少。在这里，我们分析了与番茄病原体丁香假单胞菌 pv.番茄（Pto）密切相关的丁香假单胞菌菌株的系统发育、毒力基因、宿主范围和侵袭性，包括从积雪和溪流中分离出的菌株。非农业环境中 Pto 相关菌株的种群数量估计很大，其多样性高于作物上 Pto 及其相关菌株的种群多样性。环境菌株、Pto 和其他遗传同态作物病原体的祖先被推断为经常重组，这表明丁香假单胞菌具有流行的种群结构。一些环境菌株具有与 Pto 非常相似的 III 型分泌效应子库，在番茄上的侵袭性几乎与 Pto 一样强，但宿主范围比典型的 Pto 菌株更广。我们得出结论，作物病原体可能是通过少数进化事件从非农业环境中存在的、侵袭性较弱但宿主范围较广的种群中进化而来的。
