Lehsten Veiko, Wiik Lars, Hannukkala Asko, Andreasson Erik, Chen Deliang, Ou Tinghai, Liljeroth Erland, Lankinen Åsa, Grenville-Briggs Laura
Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
Dynamic Macroecology/ Landscape dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland.
PLoS One. 2017 May 30;12(5):e0177580. doi: 10.1371/journal.pone.0177580. eCollection 2017.
Late blight (caused by Phytophthora infestans) is a devastating potato disease that has been found to occur earlier in the season over the last decades in Fennoscandia. Up until now the reasons for this change have not been investigated. Possible explanations for this change are climate alterations, changes in potato production or changes in pathogen biology, such as increased fitness or changes in gene flow within P. infestans populations. The first incidence of late blight is of high economic importance since fungicidal applications should be typically applied two weeks before the first signs of late blight and are repeated on average once a week.
We use field observations of first incidence of late blight in experimental potato fields from five sites in Sweden and Finland covering a total of 30 years and investigate whether the earlier incidence of late blight can be related to the climate.
We linked the field data to meteorological data and found that the previous assumption, used in common late blight models, that the disease only develops at relative humidity levels above 90% had to be rejected. Rather than the typically assumed threshold relationship between late blight disease development and relative humidity we found a linear relationship. Our model furthermore showed two distinct responses of late blight to climate. At the beginning of the observation time (in Sweden until the early 90s and in Finland until the 2000s) the link between climate and first incidence was very weak. However, for the remainder of the time period the link was highly significant, indicating a change in the biological properties of the pathogen which could for example be a change in the dominating reproduction mode or a physiological change in the response of the pathogen to climate.
The study shows that models used in decision support systems need to be checked and re-parametrized regularly to be able to capture changes in pathogen biology. While this study was performed with data from Fennoscandia this new pathogen biology and late blight might spread to (or already be present at) other parts of the world as well. The strong link between climate and first incidence together with the presented model offers a tool to assess late blight incidence in future climates.
晚疫病（由致病疫霉引起）是一种极具破坏性的马铃薯病害，在过去几十年里，在斯堪的纳维亚半岛发现其在生长季早期出现。到目前为止，尚未对这种变化的原因进行调查。这种变化的可能解释包括气候改变、马铃薯生产变化或病原体生物学特性变化，例如致病疫霉种群适应性增强或基因流动改变。晚疫病的首次发病具有很高的经济重要性，因为通常应在晚疫病首次出现症状前两周施用杀菌剂，并且平均每周重复施用一次。
我们利用瑞典和芬兰五个地点的实验马铃薯田晚疫病首次发病的田间观测数据，这些数据涵盖了30年，并研究晚疫病发病提前是否与气候有关。
我们将田间数据与气象数据相关联，发现常用的晚疫病模型中关于该病仅在相对湿度高于90%时才会发生的先前假设必须被摒弃。我们发现晚疫病发病与相对湿度之间并非典型的阈值关系，而是线性关系。我们的模型还显示了晚疫病对气候的两种不同反应。在观测期开始时（在瑞典直到90年代初，在芬兰直到21世纪初），气候与首次发病之间的联系非常微弱。然而，在该时间段的其余时间里，这种联系非常显著，这表明病原体的生物学特性发生了变化，例如可能是主要繁殖方式的改变或病原体对气候反应的生理变化。
该研究表明，决策支持系统中使用的模型需要定期检查和重新参数化，以便能够捕捉病原体生物学特性的变化。虽然这项研究是基于斯堪的纳维亚半岛的数据进行的，但这种新的病原体生物学特性和晚疫病可能也会传播到世界其他地区（或已经存在于其他地区）。气候与首次发病之间的紧密联系以及所提出的模型为评估未来气候下的晚疫病发病率提供了一种工具。
