Plant–fungal associations are frequently key drivers of plant invasion success. Foliar fungi can benefit their invasive hosts by enhancing growth promotion, disease resistance and environmental stress tolerance. However, the roles of foliar fungi may vary when a given invasive plant faces different stresses. In this study, we designed three independent experiments to evaluate the effects of a foliar fungus, Colletotrichum sp., on the growth performance of the invasive plant Ageratina adenophora under different soil conditions, as well as the responses of A. adenophora to the foliar fungal pathogen Diaporthe helianthi and to herbivory. We found that the soil type was the most influential factor for the growth of A. adenophora. The role of the foliar fungus Colletotrichum sp. varied in the different soil types but generally adversely affected leaf development in A. adenophora. Colletotrichum sp. may be a weak latent foliar pathogen that can enhance the pathogenicity of D. helianthi on leaves of A. adenophora and marginally reduce signs of herbivory by natural insects in the wild on A. adenophora seedlings. In general, the benefits of the foliar fungus Colletotrichum to the fitness of A. adenophora are not significant in the context of this experimental design. However, our data highlight the need to consider both aboveground and belowground biota in different soil habitats when evaluating the effects of foliar fungi.

中文翻译：

---

评价叶片真菌介导的入侵植物紫茎泽兰地下和地下敌人的相互作用

植物-真菌协会通常是植物入侵成功的关键驱动力。叶真菌可以通过增强生长促进能力，抗病能力和环境压力耐受性来使入侵宿主受益。但是，当给定的入侵植物面临不同的胁迫时，叶真菌的作用可能会有所不同。在这项研究中，我们设计了三个独立的实验，以评估不同土壤条件下叶真菌真菌炭疽菌（Colletotrichum sp。）对入侵植物紫茎泽兰的生长性能以及紫茎泽兰对叶真菌的反应的影响。病原菌是菊苣和食草动物。我们发现土壤类型是影响土壤生长的最主要因素。紫茎泽兰。叶面真菌Colletotrichum sp。的作用。在不同的土壤类型中变化很大，但通常对紫茎泽兰的叶片发育产生不利影响。炭疽病菌。可能是一个潜在的薄弱叶病原体，可以提高的致病性D. helianthi上的叶紫茎泽兰和边缘自然昆虫在野外减少取食的迹象紫茎泽兰幼苗。一般来说，叶真菌炭疽菌对紫茎泽兰的适应性有益在此实验设计中并不重要。但是，我们的数据强调了在评估叶面真菌的影响时，需要同时考虑不同土壤生境中的地上和地下生物区系。