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 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.

A global pangenome for the wheat fungal pathogen Pyrenophora tritici-repentis and prediction of effector protein structural homology

“…These resources can be used to monitor Ptr variations potentially involved in pathogenicity. As Ptr is commonly shown to infect wheat in combination with other necrotrophic pathogens [ 88 ], the future ability to simultaneously monitor such changes in multiple necrotrophic species may enhance pathogen monitoring activities within a wider framework of crop protection activities.…”

Air-seq: Measuring air metagenomic diversity in an agricultural ecosystem

“…The latter disease was once common in the UK but has been very largely replaced by Septoria tritici blotch caused by Z. tritici . A PCR-based analysis of leaves of wheat in the UK found up to 100 % of samples to contain DNA of Z. tritici with 20 % and 30 %, respectively containing P. tritici-repentis or P. nodorum of samples to these pathogens [49]. The detection of P. tritici-repentis and P. nodorum in the Air-seq samples indicates that these pathogens are present on alternative hosts from which spores are released and that could pose a threat to UK wheat crops if environmental conditions are conducive to infection.…”

“…The copyright holder for this preprint this version posted December 15, 2022. ; https://doi.org/10.1101/2022.12.13.520298 doi: bioRxiv preprint % and 30 %, respectively containing P. tritici-repentis or P. nodorum of samples to these pathogens [49]. The detection of P. tritici-repentis and P. nodorum in the Air-seq samples indicates that these pathogens are present on alternative hosts from which spores are released and that could pose a threat to UK wheat crops if environmental conditions are conducive to infection.…”

A global pangenome for the wheat fungal pathogen Pyrenophora tritici-repentis and prediction of effector protein structural homology

“…These resources can be used to monitor Ptr variations potentially involved in pathogenicity. As Ptr is commonly shown to infect wheat in combination with other necrotrophic pathogens (Justesen, Corsi et al 2021), the future ability to simultaneously monitor such changes in multiple necrotrophic species may enhance pathogen monitoring activities within a wider framework of crop protection activities.…”