E-mail: therese.bengtsson@slu.se

Wheat is a primary provider of daily calories and protein for humans worldwide. However, the pursuit of high yield and grain quality faces persistent challenges due to biotic and abiotic stresses adversely affecting wheat performance. For instance, the expanding organic wheat production in Europe has led to an increase in the incidences of common bunt (CB) caused by Tilletia tritici and Tilletia laevis. This disease can significantly reduce grain quality and cause yield losses of up to 40%. While chemical seed treatments are effective in conventional farming, organic agriculture relies on resistant cultivars.

The primary aim of our project is to ensure the production of bunt-free organic wheat. To accomplish this, we will undertake two main objectives: 1) study the distribution, population structure and virulence spectra of the pathogen and 2) identify resistance genes in wheat to be targeted by the national breeding program.

In collaboration with the extension service, CB-infected wheat spikes were collected from farmer’s fields and the bunts were examined under the microscope to identify the causal species based on teliospore morphology. Furthermore, species confirmation and population genetic studies were conducted through de-novo sequencing and Illumina sequencing of collected samples.

A virulence spectrum test of the collected Tilletia lineages using a CB differential set (Bt0 to Bt15 and BtP) is ongoing using accessions with one or more race-specific resistance genes (R-genes) complemented with Swedish winter wheat cultivars, including the resistant cultivars Stava, Festival and Hallfreda, and the susceptible cultivars Brons and Kranich.

Preliminary results reveal T. tritici prevalence across regions, with varying genetic diversity and demonstrated virulence against Bt2, Bt4, Bt7, Bt8, Bt9, Bt13, and Bt15. While virulence against Bt2, Bt7 and Bt13 were common among the tested Tilletia lineages, no virulence against Bt1 and Bt11 was found.

Notably, a few aggressive lineages with high infection rates in Hallfreda and Festival were observed, cultivars considered resistant to CB. The findings from this project will enhance understanding of CB epidemiology and support breeding efforts towards the development of resistant cultivars.