Genetic analysis of resistance in Triticum spp. to newly emerging races of wheat stem rust

Ing. Ondřej Zelba

Disertační práce

Abstract:

Stem rust of wheat (Triticum spp.) is one of the most significant fungal diseases in agriculture. Its research and breeding for resistance pays special attention to the tropics and subtropics, where yield losses are most severe. In recent years, however, the disease has also been reappearing in the European continent through incursions of novel races from tropics and subtropics and the pathogen population is adapting to the mild climate. This thesis analyses the basis of genetic resistance of cultivars grown in the Czech Republic in light of virulence of novel pathogen races. A panel of locally grown wheat cultivars is tested for presence of resistance genes using molecular markers. Results of marker assays are compared to field trials and greenhouse phenotypic tests using characterized pathogen races. Additionally, several Kompetitive allele-specific PCR (KASP) markers linked to resistance genes Sr8a and Sr11 are tested on local wheat germplasm for the first time to validate them for detection of the resistance genes. Furthermore, adult plant resistance phenotyping is undertaken with a small subset of cultivars to describe their resistance into more detail. Quantification of disease severity is done using visual assessment, image analysis with machine learning, and quantification of chitin in samples. Results of marker assays suggest that gene Sr38 is present most frequently (63.8%). While cultivars with this gene show lower disease severity in the non-race specific field trials in previous years, isolates collected in 2020 season are mostly virulent to it. Resistance genes Sr31 and Sr24 are present with 10.3% and 13.8% frequencies and are still effective towards present races. Cultivars with a combination of two out of all the tested genes show best results in field trials compared to cultivars with one or no detected resistance genes. Adult plant phenotyping demonstrated that there is adult plant resistance in some cultivars which is not otherwise discernible. Image analysis using Trainable Weka Segmentation was performed successfully with both seedling and adult plant samples and usage of this easy method of quantifying symptoms of rust disease is validated here. KASP markers linked to genes Sr8a and Sr11 show conflicting results and further phenotypic tests will have to be done to prove their applicability. This thesis uses molecular methods and disease phenotyping to provide an up-to-date overview of stem rust resistance of wheat in Czech cultivars, useful for breeders, farmers, and future researchers.

Keywords

resistance genes, fungal pathogens, stem rust, wheat, molecular markers

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 22. 3. 2024

Obhajoba závěrečné práce

• Vedoucí: Ing. Iva Viehmannová, Ph.D.
• Oponent: Jana Mazáková, Ing., Ph.D., Michaela Sedlářová, Ing., externi, Zdeněk Nesvadba, externi

Česká zemědělská univerzita v Praze

Fakulta tropického zemědělství

Doktorský studijní program / obor:
Zemědělská specializace / Tropical Agrobiology and Bioresource Management