Reynolds Gregory J, Gordon Thomas R, McRoberts Neil
Forest Health Protection, U.S. Forest Service, 333 Broadway Blvd. SE, Albuquerque, NM 87102, USA.
Department of Plant Pathology, University of California, One Shields Avenue, Davis, CA 95616, USA.
Plants (Basel). 2019 Jul 12;8(7):219. doi: 10.3390/plants8070219.
Systemic acquired resistance (SAR) is a mechanism through which plants may respond to initial challenge by a pathogen through activation of inducible defense responses, thereby increasing resistance to subsequent infection attempts. Fitness costs are assumed to be incurred by plants induced for SAR, and several studies have attempted to quantify these costs. We developed a mathematical model, motivated by game-theoretic concepts, to simulate competition between hypothetical plant populations with and without SAR to examine conditions under which the phenomenon of SAR may have evolved. Data were gathered from various studies on fitness costs of induced resistance on life history traits in different plant hosts and scaled as a proportion of the values in control cohorts in each study (i.e., healthy plants unprimed for SAR). With unprimed healthy control plants set to a fitness value of 1, primed healthy plants incurred a fitness cost of about 10.4% (0.896, = 157), primed diseased plants incurred a fitness cost of about 15.5% (0.845, = 54), and unprimed diseased plants incurred a fitness cost of about 28.9% (0.711, = 69). Starting from a small proportion of the population (0.5%) and competing against a population with constitutive defenses alone in stochastic simulations, the SAR phenotype almost always dominated the population after 1000 generations when the probability of disease was greater than or equal to 0.5 regardless of the probability for priming errors.
系统获得性抗性（SAR）是植物通过激活诱导防御反应来应对病原体初次挑战的一种机制，从而增强对后续感染的抗性。人们认为诱导SAR的植物会付出适应性代价，已有多项研究试图对这些代价进行量化。我们基于博弈论概念开发了一个数学模型，以模拟具有和不具有SAR的假设植物种群之间的竞争，从而研究SAR现象可能进化的条件。数据来自关于不同植物宿主中诱导抗性对生活史特征适应性代价的各种研究，并按每项研究中对照群体（即未进行SAR预处理的健康植物）的值的比例进行缩放。将未预处理的健康对照植物的适应性值设为1，预处理的健康植物的适应性代价约为10.4%（0.896，n = 157），预处理的患病植物的适应性代价约为15.5%（0.845，n = 54），未预处理的患病植物的适应性代价约为28.9%（0.711，n = 69）。在随机模拟中，从种群的一小部分（0.5%）开始，与仅具有组成型防御的种群竞争，当疾病概率大于或等于0.5时，无论引发错误的概率如何，SAR表型在1000代后几乎总是占据种群主导地位。
