GWAS-Assisted Genomic Prediction to Predict Resistance to Septoria Tritici Blotch in Nordic Winter Wheat at Seedling Stage.

Firuz Odilbekov,Aakash Chawade,Alexander Koc,Rita Armoniené,Jan Svensson

doi:10.3389/fgene.2019.01224

Abstract

Septoria tritici blotch (STB) disease caused by Zymoseptoria tritici is one of the most damaging diseases of wheat causing significant yield losses worldwide. Identification and employment of resistant germplasm is the most cost-effective method to control STB. In this study, we characterized seedling stage resistance to STB in 175 winter wheat landraces and old cultivars of Nordic origin. The study revealed significant (p < 0.05) phenotypic differences in STB severity in the germplasm. Genome-wide association analysis (GWAS) using five different algorithms identified ten significant markers on five chromosomes. Six markers were localized within a region of 2 cM that contained seven candidate genes on chromosome 1B. Genomic prediction (GP) analysis resulted in a model with an accuracy of 0.47. To further improve the prediction efficiency, significant markers identified by GWAS were included as fixed effects in the GP model. Depending on the number of fixed effect markers, the prediction accuracy improved from 0.47 (without fixed effects) to 0.62 (all non-redundant GWAS markers as fixed effects), respectively. The resistant genotypes and single-nucleotide polymorphism (SNP) markers identified in the present study will serve as a valuable resource for future breeding for STB resistance in wheat. The results also highlight the benefits of integrating GWAS with GP to further improve the accuracy of GP.

Highlights

Septoria tritici blotch (STB) disease caused by fungal pathogen Zymoseptoria tritici is one of the devastating foliar diseases of wheat in the temperate regions worldwide
The Z. tritici isolate was evaluated on a differential set of wheat cultivars with known Stb resistance genes (Supplementary Figure 1)
Tukey multiple comparison test showed that the genotypes Kranich, Starke, Galicia, and Cymbal exhibited a higher level of resistance to STB while the lower level of resistance was found in genotypes such as Penta, Sejet, Svea I, and Gluten

Summary

Introduction

Septoria tritici blotch (STB) disease caused by fungal pathogen Zymoseptoria tritici is one of the devastating foliar diseases of wheat in the temperate regions worldwide. STB causes significant yield losses and additional fungicide expenses (Fones and Gurr, 2015; Torriani et al, 2015). The annual harvest losses reach 5% to 10% in the biggest EU wheat producing countries (Fones and Gurr, 2015). Cultivation of resistant cultivars in combination with fungicide application is the main strategy to control the disease. A major problem of the intensive use of fungicides is that many populations of Z. tritici have rapidly evolved resistance to its active agents (Torriani et al, 2009; Wieczorek et al, 2015; Cheval et al, 2017).

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