Ramachandran Sreedevi, Renault Sylvie, Markham John, Verdugo Jaime, Albornoz Marta, Avila-Sakar Germán
Department of Biology, The University of Winnipeg, Winnipeg, MB R3B 2G3, Canada.
Department of Plant Agriculture, University of Guelph, Guelph, ON N1G 2W1, Canada.
Plants (Basel). 2020 Aug 26;9(9):1096. doi: 10.3390/plants9091096.
Soil nitrogen (N) supplementation via fertilizers may increase crop yields substantially. However, by increasing tissue N content, added N can make plants more attractive to herbivores, effectively reducing their resistance to herbivores (ability to avoid herbivore damage). In turn, greater pest infestation may cause more severe reductions in fruit production than a moderate N scarcity. In this study, we tested whether lower N supplementation results in greater resistance to whiteflies and lower fruit production in four tomato varieties. We assessed the effects of N availability on tolerance to herbivores (degree to which fitness is affected by damage) and tested for the long-hypothesized trade-off between resistance and tolerance. Plants grown at half of an agronomically recommended amount of N had greater resistance without a significant drop in fruit production. Tomato varieties differed in resistance and tolerance to whiteflies, and showed a clear trade-off between these modes of defense. Root:shoot ratios were greater at lower N, but had no clear relation to tolerance. We estimated that the economic benefit of decreasing N addition almost fully compensates for losses due to lower tomato production. Additionally, lower fertilization rates would contribute to reduce environmental costs of large-scale use of agrochemicals.
通过肥料补充土壤氮（N）可大幅提高作物产量。然而，额外添加的氮会增加植物组织中的氮含量，从而使植物对食草动物更具吸引力，有效降低其对食草动物的抗性（避免食草动物损害的能力）。反过来，虫害加剧可能比适度的氮缺乏更严重地降低果实产量。在本研究中，我们测试了较低的氮补充量是否会使四个番茄品种对白粉虱的抗性增强以及果实产量降低。我们评估了氮有效性对食草动物耐受性（适合度受损害影响的程度）的影响，并测试了长期以来所假设的抗性与耐受性之间的权衡关系。以农学推荐量一半的氮水平种植的植株具有更强的抗性，且果实产量没有显著下降。番茄品种在对白粉虱的抗性和耐受性方面存在差异，并且在这些防御模式之间表现出明显的权衡关系。较低氮水平下根冠比更大，但与耐受性没有明显关系。我们估计，减少氮添加量带来的经济效益几乎完全可以弥补番茄产量降低造成的损失。此外，较低的施肥率将有助于降低大规模使用农用化学品的环境成本。
