Sammendrag
Key message A locus on wheat chromosome 2A was found to control feld resistance to both leaf and glume blotch
caused by the necrotrophic fungal pathogen Parastagonospora nodorum.
Abstract The necrotrophic fungal pathogen Parastagonospora nodorum is the causal agent of Septoria nodorum leaf blotch
and glume blotch, which are common wheat (Triticum aestivum L.) diseases in humid and temperate areas. Susceptibility
to Septoria nodorum leaf blotch can partly be explained by sensitivity to corresponding P. nodorum necrotrophic efectors
(NEs). Susceptibility to glume blotch is also quantitative; however, the underlying genetics have not been studied in detail.
Here, we genetically map resistance/susceptibility loci to leaf and glume blotch using an eight-founder wheat multiparent
advanced generation intercross population. The population was assessed in six feld trials across two sites and 4 years. Seedling infltration and inoculation assays using three P. nodorum isolates were also carried out, in order to compare quantitative
trait loci (QTL) identifed under controlled conditions with those identifed in the feld. Three signifcant feld resistance QTL
were identifed on chromosomes 2A and 6A, while four signifcant seedling resistance QTL were detected on chromosomes
2D, 5B and 7D. Among these, QSnb.niab-2A.3 for feld resistance to both leaf blotch and glume blotch was detected in Norway and the UK. Colocation with a QTL for seedling reactions against culture fltrate from a Norwegian P. nodorum isolate
indicated the QTL could be caused by a novel NE sensitivity. The consistency of this QTL for leaf blotch at the seedling and
adult plant stages and culture fltrate infltration was confrmed by haplotype analysis. However, opposite efects for the leaf
blotch and glume blotch reactions suggest that diferent genetic mechanisms may be involved.
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