Min Lin, Andrea Ficke, Jon Arne Dieseth & Morten Lillemo

Theoretical and Applied Genetics December 2022; vol. 135: 4169–4182

Key message

A new QTL for SNB, QSnb.nmbu-2AS, was found in both winter and spring wheat panels that can greatly advance SNB resistance breeding

Abstract

Septoria nodorum blotch (SNB), caused by the necrotrophic fungal pathogen Parastagonospora nodorum, is the dominant leaf blotch pathogen of wheat in Norway. Resistance/susceptibility to SNB is a quantitatively inherited trait, which can be partly explained by the interactions between wheat sensitivity loci (Snn) and corresponding P. nodorum necrotrophic effectors (NEs). Two Nordic wheat association mapping panels were assessed for SNB resistance in the field over three to four years: a spring wheat and a winter wheat panel (n = 296 and 102, respectively). Genome-wide association studies found consistent SNB resistance associated with quantitative trait loci (QTL) on eleven wheat chromosomes, and ten of those QTL were common in the spring and winter wheat panels. One robust QTL on the short arm of chromosome 2A, QSnb.nmbu-2AS, was significantly detected in both the winter and spring wheat panels. For winter wheat, using the four years of SNB field severity data in combination with five years of historical data, the effect of QSnb.nmbu-2AS was confirmed in seven of the nine years, while for spring wheat, the effect was confirmed for all tested years including the historical data from 2014 to 2015. However, lines containing the resistant haplotype are rare in both Nordic spring (4.0%) and winter wheat cultivars (15.7%), indicating the potential of integrating this QTL in SNB resistance breeding programs. In addition, clear and significant additive effects were observed by stacking resistant alleles of the detected QTL, suggesting that marker-assisted selection can greatly facilitate SNB resistance breeding.

See https://link.springer.com/article/10.1007/s00122-022-04210-z

Fig.1: Manhattan plots of marker-trait associations for corrected SNB disease severity in the spring wheat panel. From top to bottom are Manhattan plots for the years 2016, 2017, 2018, and mean of the three years. The 0.1 percentile threshold is indicated as a horizontal line in each subplot. Dots above the threshold indicate significant markers; red dots indicate markers above the − log₁₀(p) 4.0 threshold. Important QTL (significant in at least two environments or one year and mean across years) are labeled with yellow rectangles