Hidden in plain sight: a molecular field survey of three wheat leaf blotch fungal diseases in North-Western Europe shows co-infection is widespread

Abstract Wheat ( Triticum aestivum L.) yields are commonly affected by foliar infection fungal pathogens. Of these, three wheat leaf blotch diseases, septoria nodorum (SNB), tan spot (TS) and tritici (STB), caused Parastagonospora Pn ), Pyrenophora tritici-repentis Ptr ) Zymoseptoria Zt respectively, induce major yield losses. Infection results in necrotic areas on the leaf, it is often difficult to determine underlying causative pathogen from visible symptoms alone, especially mixed infections. Here, a regional survey of 330 samples collected across seasons (years 2015–2017) four north-west European countries was undertaken. Using quantitative polymerase chain reaction (qPCR) assays specific for each pathogen, as well disease assessment materials, distinct differences were identified. Two-thirds (65%) all harbored at least two Norway had high SNB abundance, but also showed infections SNB, TS STB. In Germany, prevalent, with STB common. Danish possessed pathogens, followed SNB. The UK prevalence minimal occurrence Across samples, qPCR identified , 90%, 54% 57% respectively. For average levels via visual modest positive correlation DNA concentrations (R 2 = 0.13–0.32). Overall, our study highlights that common widespread, important implications management breeding strategies.