Genome evolution of a pandemic clonal lineage of the wheat blast fungus

稻瘟病菌是引起小麦稻瘟病的病原菌，对小麦生产具有毁灭性的影响。国际玉米和小麦改良中心(CIMMYT)在一份优先简报中将小麦稻瘟病描述为“致命和令人困惑的敌人”。CIMMYT列出的四个优先事项中的两个是“全球监测疾病的外观、运动和进化”和“遗传和流行病学研究”。1985年，该疾病最初在巴西麦田中被发现，并在接下来的几年里迅速蔓延到南美大陆的大部分地区。2016年，南美以外的第一次小麦瘟疫疫情袭击了孟加拉国，影响了超过1.5万公顷的田地，造成小麦产量的巨大损失。不到两年后，赞比亚农民也受到了小麦瘟疫大流行的影响，这在非洲大陆还是第一次。直到最近，还没有证实这次大流行是由在两大洲之间传播的同一病原体引起的，还是由其他稻瘟病菌菌株将寄主物种转移到小麦上的结果。为了回答这个问题，我们在伦敦大学学院塞恩斯伯里实验室的团队和世界各地的几个合作者通过OpenWheatBlast开放科学倡议处理和分析了来自三大洲的大流行小麦瘟疫样本。分子分析将赞比亚和孟加拉国的病原菌群体与起源于南美洲的一个名为B71的大流行克隆联系在一起。我们的初步分析显示，这个大流行克隆的小麦稻瘟病菌正在进化。该项目将在未来几年继续并扩大在非洲的小麦稻瘟病基因组监测，并产生基因组学知识，以指导应对大流行。更具体地说，我们将快速识别新变异的出现，确定支撑基因变化的确切性质，并评估这些变异对疾病严重性的影响。更好地了解大流行小麦稻瘟菌是如何进化的，应该为以知识为导向的疾病管理和培育能够更好地抵御疾病的小麦植株提供指导。我们的长期目标是将基因组监测完全整合到应对植物健康紧急情况中，以提高我们保护植物免受作物疾病侵袭的能力。

Magnaporthe oryzae pathotype Triticum, the causal agent of wheat blast, is a fungus with devastating implications for the wheat crop. The International Maize and Wheat Improvement Center (CIMMYT) has described wheat blast in a Priority Brief as a "deadly and baffling foe". "Global monitoring of disease appearances, movement, and evolution" and "Genetic and epidemiological research" are two of the four priorities listed by CIMMYT.The disease was originally detected in Brazilian wheat fields in 1985 and quickly spread over most of the South American continent in the following years. In 2016, the first wheat blast pandemic beyond South America hit Bangladesh and affected more than 15 000 hectares of fields, causing huge losses in wheat yield. Less than two years later, Zambian farmers were also struck by the wheat blast pandemic, a first for the African continent. Until recently, there has been no confirmation if this pandemic was caused by the same pathogen which had travelled between the continents or if they were the result of other Magnaporthe oryzae pathogen strains shifting their host species to wheat.To answer this question, our teams at The Sainsbury Laboratory, University College London, and several collaborators throughout the world processed and analysed samples of pandemic wheat blast from the three continents through the OpenWheatBlast open science initiative. Molecular analyses linked the pathogen populations in Zambia and Bangladesh to a single pandemic clone called B71 that originated in South America.Our preliminary analyses revealed that this pandemic clone of the wheat blast fungus is evolving. This project will continue and expand wheat blast genomic surveillance in Africa over the coming years and generate genomics-informed knowledge to guide the response to the pandemic. More specifically, we will rapidly identify the emergence of new variants, determine the precise nature of the underpinning genetic changes, and evaluate the impact of these variants on disease severity. A better understanding of how the pandemic wheat blast fungus evolves should inform knowledge-guided disease management and breeding wheat plants that are better able to resist diseases. Our long-term aim is to fully integrate genomic surveillance in the response to plant health emergencies to improve our capacity to protect plants against crop diseases.