Wheat (Triticum aestivum L.) yields are commonly affected by foliar infection by fungal pathogens. Of these, three wheat leaf blotch fungal diseases, septoria nodorum blotch (SNB), tan spot (TS) and septoria tritici blotch (STB), caused by Parastagonospora nodorum (Pn), Pyrenophora tritici-repentis (Ptr) and Zymoseptoria tritici (Zt), respectively, induce major yield losses. Infection results in necrotic areas on the leaf, and it is often difficult to determine the underlying causative pathogen from visible symptoms alone, especially in mixed infections. Here, a regional survey of 330 wheat samples collected across three seasons (years 2015–2017) from four north-west European countries was undertaken. Using quantitative polymerase chain reaction (qPCR) assays specific for each pathogen, as well as disease assessment of leaf materials, distinct regional differences were identified. Two-thirds (65%) of all samples harbored at least two of the three pathogens. Norway had high SNB abundance, but also showed mixed infections of SNB, TS and STB. In Germany, TS was prevalent, with STB also common. Danish samples commonly possessed all three pathogens, with STB prevalent, followed by TS and SNB. The UK had a major prevalence of STB with minimal occurrence of TS and SNB. Across all samples, qPCR identified Zt, Pn and Ptr in 90%, 54% and 57% of samples, respectively. For each pathogen, average disease levels via visual assessment showed modest positive correlation with fungal DNA concentrations (R² = 0.13–0.32). Overall, our study highlights that the occurrence of mixed infection is common and widespread, with important implications for wheat disease management and breeding strategies.

小麦 ( Triticum aestivum L.) 产量通常受到真菌病原体叶面感染的影响。其中，小麦叶斑病真菌病害包括黑斑病菌病（SNB）、棕褐色斑病（TS）和小麦斑病菌病（STB），由结节孢子菌（Pn）、小麦核菌病菌（Ptr）和小麦黑斑病菌（Zt）引起。)，分别导致主要的产量损失。感染会导致叶片坏死区域，通常很难仅从可见的症状中确定潜在的致病病原体，尤其是在混合感染中。在这里，对来自四个西北欧国家的三个季节（2015-2017 年）收集的 330 个小麦样本进行了区域调查。使用特定于每种病原体的定量聚合酶链反应 (qPCR) 分析以及叶片材料的疾病评估，确定了明显的区域差异。所有样本的三分之二 (65%) 至少含有三种病原体中的两种。挪威有很高的 SNB 丰度，但也表现出 SNB、TS 和 STB 的混合感染。在德国，TS 很普遍，STB 也很常见。丹麦样本通常具有所有三种病原体，STB 流行，其次是TS和SNB。英国的 STB 流行率很高，TS 和 SNB 的发生率极低。在所有样本中，qPCR 鉴定Zt、Pn和Ptr 分别在 90%、54% 和 57% 的样品中。对于每种病原体，通过目测评估的平均疾病水平与真菌 DNA 浓度呈适度正相关（R ²  = 0.13–0.32）。总的来说，我们的研究强调混合感染的发生是普遍和普遍的，对小麦病害管理和育种策略具有重要意义。