Vyska Martin, Cunniffe Nik, Gilligan Christopher
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, UK
Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, UK.
J R Soc Interface. 2016 Oct;13(123). doi: 10.1098/rsif.2016.0451.
The deployment of crop varieties that are partially resistant to plant pathogens is an important method of disease control. However, a trade-off may occur between the benefits of planting the resistant variety and a yield penalty, whereby the standard susceptible variety outyields the resistant one in the absence of disease. This presents a dilemma: deploying the resistant variety is advisable only if the disease occurs and is sufficient for the resistant variety to outyield the infected standard variety. Additionally, planting the resistant variety carries with it a further advantage in that the resistant variety reduces the probability of disease invading. Therefore, viewed from the perspective of a grower community, there is likely to be an optimal trade-off and thus an optimal cropping density for the resistant variety. We introduce a simple stochastic, epidemiological model to investigate the trade-off and the consequences for crop yield. Focusing on susceptible-infected-removed epidemic dynamics, we use the final size equation to calculate the surviving host population in order to analyse the yield, an approach suitable for rapid epidemics in agricultural crops. We identify a single compound parameter, which we call the efficacy of resistance and which incorporates the changes in susceptibility, infectivity and durability of the resistant variety. We use the compound parameter to inform policy plots that can be used to identify the optimal strategy for given parameter values when an outbreak is certain. When the outbreak is uncertain, we show that for some parameter values planting the resistant variety is optimal even when it would not be during the outbreak. This is because the resistant variety reduces the probability of an outbreak occurring.
部署对植物病原体具有部分抗性的作物品种是疾病控制的重要方法。然而，种植抗性品种的益处与产量损失之间可能会出现权衡，即在无病害情况下，标准感病品种的产量高于抗性品种。这就带来了一个两难困境：只有在病害发生且抗性品种的产量足以超过受感染的标准品种时，部署抗性品种才是明智的。此外，种植抗性品种还有一个额外的优势，即抗性品种降低了病害侵袭的概率。因此，从种植者群体的角度来看，抗性品种可能存在一个最优权衡，进而存在一个最优种植密度。我们引入一个简单的随机流行病学模型来研究这种权衡及其对作物产量的影响。针对易感 - 感染 - 移除的流行动态，我们使用最终规模方程来计算存活的寄主种群数量，以便分析产量，这种方法适用于农作物中的快速流行病。我们确定了一个单一的复合参数，我们称之为抗性效力，它综合了抗性品种在易感性、传染性和耐久性方面的变化。我们使用这个复合参数来绘制策略图，当疫情确定时，这些图可用于确定给定参数值下的最优策略。当疫情不确定时，我们表明对于某些参数值，即使在疫情期间种植抗性品种不是最优选择，但种植抗性品种仍是最优的。这是因为抗性品种降低了疫情发生的概率。
