Organic wheat threatened by common bunt – solutions sought in genetic resistance

Common bunt affects both winter and spring wheat and, to some extent, barley. In conventional farming, the disease is managed with fungicides.

Organic farming, however, is vulnerable to common bunt. The disease renders the crop unfit for consumption.

– The seeds turn dark and smell of rotting fish, says Laurène Mailhan.

She is a doctoral student at the Department of Plant Breeding at SLU in Alnarp and studies the disease in wheat.

She explains that the most effective way for farmers to avoid the foul-smelling fungal disease is to grow resistant wheat cultivars. However, in Sweden, only one such cultivar bred for organic farming is currently known. It is called Stava and entered the market in 1995.

In her project, Laurène Mailhan will examine Stava more closely in order to understand the genetics behind its resistance. This knowledge could potentially be used in plant breeding to create more resistant cultivars in the future.

– There are different races of common bunt in Sweden, and Stava is resistant to all of them. In my project, we are trying to understand the resistance mechanisms. There are some suspicions about which genes in Stava influence resistance, but the research is not entirely conclusive, she says.

The project is important because the cultivation of organic wheat has increased in Sweden over the past twenty years – and with it, the incidence of common bunt.

– We need to understand what is happening with this disease, how we can fight against it in organic agriculture, and how it can be prevented in the long term. I hope we produce results that will be useful to farmers.

Learned about common bunt during exchange studies

Laurène Mailhan began her doctoral position at SLU a year ago. Before that, she was an exchange student at the university. She completed her master’s degree in plant breeding in Alnarp.

During her exchange studies, she worked with common bunt for the first time and took part in greenhouse experiments and field trials.

– It was exciting to see that something is going on between the different wheat genotypes that we do not fully understand. I also enjoyed the teamwork, she says.

She likes having a project to dig into and has always wanted to pursue a doctorate. Originally, however, her interests lay with animals rather than plants.

– I spent two years at a preparatory school in France to become a veterinarian. Then we had a course module where we had to dissect a flower to learn about plant families, and I found it super interesting.

A fascination with plants runs in the family, too.

– My grandmother was a pharmacist and knew everything about plants, and I loved talking to her about it. She told me she would have loved to do agronomy studies, but in her time, it was not allowed for women to do so in France.

Understanding genetic resistance in wheat

Laurène Mailhan will explore the genetic defence mechanisms in Stava and conduct microscopic studies of what happens when the cultivar encounters the disease.

– The aim is to find out which mechanisms are activated at the early stages of infection, she says.

Another part of the project involves mapping which races of common bunt occur in Sweden by collecting samples from infected fields.

– We use these infected samples to obtain spores which we use to infect different wheat cultivars. We then sow them, wait until the spikes emerge, and assess which genotypes have been infected by which races.

The pathogen’s genetics: an unexplored area

Towards the end of the project, Laurène Mailhan will also attempt to gain a better understanding of the pathogen’s own genetics.

– Almost everything we know about common bunt focuses on the plant side. We know very little about the pathogen side and which genes are involved there, so I will perform some analyses.

She expects this to be one of the most challenging parts of the project, as she enters a largely unexplored area with regards to this specific pathogen. But she is eager to try.

– In the worst case, if it does not work, that is fine too. It is a risk, but I am happy to take it.