Précigout Pierre-Antoine, Claessen David, Robert Corinne
First and second authors: Institut de Biologie de l'Ecole Normale Supérieure, CNRS-ENS-INSERM UMR8197, Ecole Normale Supérieure, 46 rue d'Ulm, 75005 Paris; and first and third authors: UMR ECOSYS INRA, AgroParisTech, Université Paris-Saclay, 78850 Thiverval-Grignon, France.
Phytopathology. 2017 Oct;107(10):1256-1267. doi: 10.1094/PHYTO-01-17-0019-R. Epub 2017 Jun 21.
Crop pathogens are known to rapidly adapt to agricultural practices. Although cultivar resistance breakdown and resistance to pesticides have been broadly studied, little is known about the adaptation of crop pathogens to fertilization regimes and no epidemiological model has addressed that question. However, this is a critical issue for developing sustainable low-input agriculture. In this article, we use a model of life history evolution of biotrophic wheat fungal pathogens in order to understand how they could adapt to changes in fertilization practices. We focus on a single pathogen life history trait, the latent period, which directly determines the amount of resources allocated to growth and reproduction along with the speed of canopy colonization. We implemented three fertilization scenarios, corresponding to major effects of increased nitrogen fertilization on crops: (i) increase in nutrient concentration in leaves, (ii) increase of leaf lifespan, and (iii) increase of leaf number (tillering) and size that leads to a bigger canopy size. For every scenario, we used two different fitness measures to identify putative evolutionary responses of latent period to changes in fertilization level. We observed that annual spore production increases with fertilization, because it results in more resources available to the pathogens. Thus, diminishing the use of fertilizers could reduce biotrophic fungal epidemics. We found a positive relationship between the optimal latent period and fertilization when maximizing total spore production over an entire season. In contrast, we found a negative relationship between the optimal latent period and fertilization when maximizing the within-season exponential growth rate of the pathogen. These contrasting results were consistent over the three tested fertilization scenarios. They suggest that between-strain diversity in the latent period, as has been observed in the field, may be due to diversifying selection in different cultural environments.
已知作物病原体能迅速适应农业生产方式。虽然品种抗性丧失和对杀虫剂的抗性已得到广泛研究，但关于作物病原体对施肥制度的适应性却知之甚少，且尚无流行病学模型探讨过这一问题。然而，这是发展可持续低投入农业的一个关键问题。在本文中，我们使用一种活体营养型小麦真菌病原体的生活史进化模型，以了解它们如何适应施肥方式的变化。我们关注病原体单一的生活史特征——潜伏期，它与冠层定殖速度一起直接决定了分配给生长和繁殖的资源量。我们实施了三种施肥方案，分别对应氮肥增加对作物的主要影响：（i）叶片中养分浓度增加；（ii）叶片寿命延长；（iii）叶片数量（分蘖）和大小增加，从而导致冠层面积增大。对于每种方案，我们使用两种不同的适合度指标来确定潜伏期对施肥水平变化的假定进化响应。我们观察到，随着施肥量增加，年度孢子产量会增加，因为这会为病原体提供更多可用资源。因此，减少化肥使用量可能会降低活体营养型真菌病害的流行程度。当在整个季节中使总孢子产量最大化时，我们发现最优潜伏期与施肥量呈正相关。相反，当使病原体在季节内的指数增长率最大化时，我们发现最优潜伏期与施肥量呈负相关。这些截然不同的结果在三种测试施肥方案中都是一致的。它们表明，田间观察到的潜伏期菌株间多样性可能是由于不同栽培环境中的多样化选择所致。
