Skelsey P, Kessel G J T, Rossing W A H, van der Werf W
Wageningen University, Department of Plant Sciences, Crop and Weed Ecology Group, P.O. Box 430, 6700 AK Wageningen, the Netherlands.
Phytopathology. 2009 Mar;99(3):290-300. doi: 10.1094/PHYTO-99-3-0290.
A spatiotemporal, integrodifference equation model of the potato late blight pathosystem is described. Formerly, the model was used in a theoretical context to analyze and predict epidemic dynamics in spatially heterogeneous mixtures of host genotypes. The model has now been modified to reflect a research interest in interactions between genotype, environment, landscape, and management. New parameter values describing host-pathogen interactions were determined and new environment-pathogen relationships included. A new analytical equation describing lesion expansion and associated necrosis has also been developed. These changes prompted a need to assess the quality of model predictions. Cultivar-isolate-specific interactions were characterized in the model using three quantitative components of resistance: infection efficiency, lesion growth rate, and sporulation intensity. These were measured on detached potato leaflets in the laboratory. Results of a sensitivity analysis illuminate the effect of different quantitative components of resistance and initial conditions on the shape of disease progress curves. Using the resistance components, the epidemic process of lesion expansion was separated from the epidemic process of lesion propagation providing two reference curves for diagnosing observed epidemics. The spatial component of the model was evaluated graphically in order to determine if realistic rates of focal expansion for potato late blight are produced. In accordance with theory, the radius of a predicted focus increased linearly with time and a constant focal velocity was reached that compared well with published experimental data. Validation data for the temporal model came from 20 late blight epidemics observed in field trials conducted in the Netherlands in 2002 and 2004. The field data and model were compared visually using disease progress curves, and numerically through a comparison of predicted and observed t(5) and t(50) points (time in days until 5 and 50% disease severity is reached, respectively) and relative areas under the disease progress curve values. Temporal model predictions were in close agreement with observational data and the ability of the model to translate measured resistance components, weather data, and initial conditions into realistic disease progress curves without the need for calibration confirms its utility as a tool in the analysis and diagnosis of epidemics.
本文描述了马铃薯晚疫病病理系统的时空积分差分方程模型。以前，该模型用于理论分析，以预测宿主基因型空间异质混合物中的流行动态。现在，该模型已被修改，以反映对基因型、环境、景观和管理之间相互作用的研究兴趣。确定了描述宿主 - 病原体相互作用的新参数值，并纳入了新的环境 - 病原体关系。还开发了一个描述病斑扩展和相关坏死的新分析方程。这些变化促使需要评估模型预测的质量。在模型中，使用抗性的三个定量成分来表征品种 - 分离物特异性相互作用：感染效率、病斑生长速率和产孢强度。这些在实验室中对离体马铃薯小叶进行了测量。敏感性分析的结果阐明了抗性的不同定量成分和初始条件对病害进展曲线形状的影响。利用抗性成分，将病斑扩展的流行过程与病斑传播的流行过程分开，提供了两条用于诊断观察到的流行病的参考曲线。以图形方式评估了模型的空间成分，以确定是否产生了马铃薯晚疫病实际的病灶扩展速率。根据理论，预测病灶的半径随时间线性增加，并达到了一个恒定的病灶扩展速度，这与已发表的实验数据相当吻合。时间模型的验证数据来自2002年和2004年在荷兰进行的田间试验中观察到的20次晚疫病流行。使用病害进展曲线直观地比较了田间数据和模型，并通过比较预测和观察到的t(5)和t(50)点（分别为达到5%和50%病害严重度所需的天数）以及病害进展曲线值下的相对面积进行了数值比较。时间模型预测与观测数据密切吻合，并且该模型无需校准就能将测量的抗性成分、气象数据和初始条件转化为实际的病害进展曲线，这证实了其作为流行病分析和诊断工具的实用性。
