Centro de Biotecnología y Genómica de Plantas UPM-INIA and E.T.S.I. Agrónomos, Universidad Politécnica de Madrid, Madrid, Spain.
J Virol. 2014 Mar;88(6):3359-68. doi: 10.1128/JVI.02980-13. Epub 2014 Jan 3.
Virus emergence is a complex phenomenon, which generally involves spread to a new host from a wild host, followed by adaptation to the new host. Although viruses account for the largest fraction of emerging crop pathogens, knowledge about their emergence is incomplete. We address here the question of whether Pepino Mosaic Virus (PepMV) emergence as a major tomato pathogen worldwide could have involved spread from wild to cultivated plant species and host adaptation. For this, we surveyed natural populations of wild tomatoes in southern Peru for PepMV infection. PepMV incidence, genetic variation, population structure, and accumulation in various hosts were analyzed. PepMV incidence in wild tomatoes was high, and a strain not yet reported in domestic tomato was characterized. This strain had a wide host range within the Solanaceae, multiplying efficiently in most assayed Solanum species and being adapted to wild tomato hosts. Conversely, PepMV isolates from tomato crops showed evidence of adaptation to domestic tomato, possibly traded against adaptation to wild tomatoes. Phylogenetic reconstructions indicated that the most probable ancestral sequence came from a wild Solanum species. A high incidence of PepMV in wild tomato relatives would favor virus spread to crops and its efficient multiplication in different Solanum species, including tomato, allowing its establishment as an epidemic pathogen. Later, adaptation to tomato, traded off against adaptation to other Solanum species, would isolate tomato populations from those in other hosts.
Virus emergence is a complex phenomenon involving multiple ecological and genetic factors and is considered to involve three phases: virus encounter with the new host, virus adaptation to the new host, and changes in the epidemiological dynamics. We analyze here if this was the case in the recent emergence of Pepino Mosaic Virus (PepMV) in tomato crops worldwide. We characterized a new strain of PepMV infecting wild tomato populations in Peru. Comparison of this strain with PepMV isolates from tomato crops, plus phylogenetic reconstructions, supports a scenario in which PepMV would have spread to crops from wild tomato relatives, followed by adaptation to the new host and eventually leading to population isolation. Our data, which derive from the analysis of field isolates rather than from experimental evolution approaches, significantly contribute to understanding of plant virus emergence, which is necessary for its anticipation and prevention.
病毒的出现是一种复杂的现象，通常涉及从野生宿主传播到新宿主，然后适应新宿主。尽管病毒占新发作物病原体的最大比例，但对它们的出现了解并不完整。我们在这里探讨了 Pepino 花叶病毒（PepMV）作为世界范围内主要的番茄病原体出现，是否可能涉及从野生植物传播到栽培植物物种和宿主适应的问题。为此，我们调查了秘鲁南部野生番茄的自然种群中 PepMV 的感染情况。分析了 PepMV 的发病率、遗传变异、种群结构和在各种宿主中的积累情况。野生番茄中 PepMV 的发病率很高，并且还鉴定出一种尚未在国内番茄中报道的菌株。该菌株在茄科中有广泛的宿主范围，在大多数测试的茄属物种中繁殖效率高，并适应野生番茄宿主。相反，来自番茄作物的 PepMV 分离株显示出适应栽培番茄的证据，可能与适应野生番茄有关。系统发育重建表明，最可能的祖先序列来自野生茄属物种。野生番茄亲缘植物中 PepMV 的高发病率有利于病毒传播到作物，并在不同的茄属物种中有效繁殖，包括番茄，从而使其成为一种流行的病原体。后来，对番茄的适应，与对其他茄属物种的适应相权衡，将番茄种群与其他宿主中的种群隔离开来。
病毒的出现是一个复杂的现象，涉及到多种生态和遗传因素，被认为涉及三个阶段：病毒与新宿主的接触、病毒对新宿主的适应以及流行病学动态的变化。我们在这里分析了 Pepino 花叶病毒（PepMV）在世界范围内最近在番茄作物中出现的情况是否属于这种情况。我们对感染秘鲁野生番茄种群的 PepMV 的一个新菌株进行了特征描述。对该菌株与来自番茄作物的 PepMV 分离株的比较，加上系统发育重建，支持了 PepMV 从野生番茄亲缘种传播到作物，然后适应新宿主，最终导致种群隔离的情景。我们的数据来自于对田间分离株的分析，而不是实验进化方法，这为理解植物病毒的出现做出了重要贡献，这是对其进行预测和预防的必要条件。
