Hatcher P E, Paul N D
1 Department of Agricultural Botany, School of Plant Sciences, The University of Reading, 2 Earley Gate, Whiteknights, Reading RG6 6AU, UK.
New Phytol. 2000 May;146(2):325-333. doi: 10.1046/j.1469-8137.2000.00646.x.
In previously reported laboratory experiments, infection of Rumex obtusifolius by the rust fungus Uromyces rumicis was decreased on leaves which had prior herbivory by the beetle Gastrophysa viridula. In this paper we investigate whether this interaction is robust for natural infection by a variety of fungi in field experiments carried out in spring and autumn with plants given different levels of nitrogen fertilization. Grazing by G. viridula led to a decrease in lesion density of Ramularia rubella and Venturia rumicis in the spring and V. rumicis and U. rumicis in the autumn experiment. For V. rumicis and U. rumicis significant reductions in lesion density occurred on the undamaged leaves of damaged plants, compared with similar leaves on undamaged plants, suggesting systemic induced resistance. This induced resistance was usually independent of the amount of nitrogen fertilization, although the inhibitory effect of grazing on R. rubella in the spring and V. rumicis in the autumn experiment was enhanced by increasing nitrogen fertilization and was inhibited by increasing nitrogen fertilization for V. rumicis in the spring. In both experiments, the lesion density of V. rumicis was greater on leaves on which R. rubella was also present, and the presence of U. rumicis in the autumn experiment was linked to a similar but greater effect on V. rumicis lesion density. We found no evidence of induced resistance by fungi against fungi in these experiments. We highlight the complex interactions between inhibitory and facilitatory processes acting on leaf fungal infection. These results are compared with the proposed molecular mechanisms of induced resistance(s) and we consider the benefits of closer integration between molecular and ecological investigations of induced resistances that occur in the field.
在先前报道的实验室实验中，酸模叶蓼被锈菌鲁米锈菌感染的情况在被甲虫绿萤叶甲预先取食过的叶片上有所减少。在本文中，我们研究了在春季和秋季进行的田间实验中，这种相互作用对于多种真菌的自然感染是否稳固，实验中使用了施加不同水平氮肥的植物。绿萤叶甲的取食导致春季风疹柱隔孢和鲁米黑星菌以及秋季鲁米黑星菌和鲁米锈菌的病斑密度降低。对于鲁米黑星菌和鲁米锈菌，受损植株未受损叶片上的病斑密度显著低于未受损植株上的类似叶片，这表明存在系统诱导抗性。这种诱导抗性通常与氮肥施用量无关，不过在春季实验中，增加氮肥施用量增强了取食对风疹柱隔孢的抑制作用，而在春季实验中，增加氮肥施用量对鲁米黑星菌的抑制作用则受到抑制。在两个实验中，同时存在风疹柱隔孢的叶片上，鲁米黑星菌的病斑密度更大，并且在秋季实验中，鲁米锈菌的存在对鲁米黑星菌病斑密度有类似但更强的影响。在这些实验中，我们没有发现真菌对真菌诱导抗性的证据。我们强调了作用于叶片真菌感染的抑制和促进过程之间的复杂相互作用。将这些结果与提出的诱导抗性分子机制进行了比较，并且我们考虑了在田间发生的诱导抗性分子和生态学研究更紧密结合的益处。
