Genetic mapping using a wheat multi-founder population reveals a locus on chromosome 2A controlling resistance to both leaf and glume blotch caused by the necrotrophic fungal pathogen Parastagonospora nodorum

Min Lin, Beatrice Corsi, Andrea Ficke, Kar-Chun Tan, James Cockram & Morten Lillemo

Theoretical and Applied Genetics Mrach 2020; volume 133, pages785–808

Key message

A locus on wheat chromosome 2A was found to control field 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 effectors (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 field trials across two sites and 4 years. Seedling infiltration and inoculation assays using three P. nodorum isolates were also carried out, in order to compare quantitative trait loci (QTL) identified under controlled conditions with those identified in the field. Three significant field resistance QTL were identified on chromosomes 2A and 6A, while four significant seedling resistance QTL were detected on chromosomes 2D, 5B and 7D. Among these, QSnb.niab-2A.3 for field resistance to both leaf blotch and glume blotch was detected in Norway and the UK. Colocation with a QTL for seedling reactions against culture filtrate 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 filtrate infiltration was confirmed by haplotype analysis. However, opposite effects for the leaf blotch and glume blotch reactions suggest that different genetic mechanisms may be involved.

See https://link.springer.com/article/10.1007/s00122-019-03507-w

Figure 3: Genetic map locations of all QTL detected in this study. QTL locations and interval sizes are indicated by bars on the right hand side of each chromosome and are based on the genetic marker information in Table 3. Field leaf blotch QTL are indicated in black, field glume blotch QTL in blue (N Norway, U UK, LB leaf blotch, GB glume blotch), and seedling QTL in green (Inoc: greenhouse inoculation, Infil: greenhouse infiltration). Of these QTL, those detected in more than one environment are indicated using a white bar, along with the designated QTL name assigned in this study