Strawberry diseases can be tested from plants and soil

In strawberry cultivation, crop damage can be caused by plant diseases, such as crown rot and red stele. Nowadays, however, plants can be tested for diseases at the time of purchase, and it is also possible to detect diseases in a soil sample taken from the farm. The development and selection of new disease-resistant varieties also increases the yield. 

Text Marianne Mustonen Photos Harri Kokko

“Over the last few years, strawberry plant deliveries have had a number of poor plants in them, and strawberry farmers haven’t been able to identify the disease. Yields have been poor and there have also been incidents of total crop failure,” says Researcher Harri Kokko from the Department of Environmental and Biological Sciences.

“In the worst case scenario, farmers can lose half of their plants right at the beginning, with the rest dying in a couple of years’ time.”

Strawberry plants are commonly imported into Finland from the Netherlands and Poland, among other places, and 15–20 million plants are planted every year. Red stele has been discovered in plants, and many farms have also been struggling with crown rot. Furthermore, last summer’s cold and damp weather worsened the disease situation.  

 

By testing plants for diseases in their country of origin, it could be ensured that only healthy plant material ends up on farms.

“Our research has been ongoing for a year now. We are testing plants for diseases and helping farmers identify them. We’ve got some guidance for this work from the US, and we’re the only ones doing this in Finland.”

A novel testing method makes it possible to identify diseases without having to isolate the plant’s DNA. The testing device is small and portable, and it can be used out in the field. Furthermore, the test results are ready within the hour.

There are still some reservations among farmers about the new testing method, because there are so many different diseases. Moreover, it is possible farmers haven’t fully grasped the competitive advantage they could gain by testing their plants beforehand yet.

“We are also developing a method that enables the identification of hidden pathogens in the soil,” Kokko says.

 

Oospores of red stele survive in soil for 15–20 years and, in the event of heavy rain and flooding, they travel in the soil and spread disease. Planting strawberry plants is expensive, and this is why it makes sense to test the soil in advance.  

Red stele pathogen can’t be removed from the soil, either, and no biocides against these diseases exist. This is why it is important to study and develop increasingly disease-resistant varieties of strawberry.

“We study the resistance of different varieties by pot experiments and by inoculating detached leaflets in the laboratory. In pot experiments, we expose strawberry varieties to pathogenic spores and study their symptoms,” Researcher Anna Toljamo explains.  

“We produce clean runner material for our experiments, as infected material naturally can’t be used.”

Although plant diseases are widespread, the researchers are confident that a solution will be found.

“Varieties that are resistant to red stele have already been developed, but these haven’t been studied with races of red stele that are prevalent in Finland.”

“Moreover, full resistance to crown rot hasn’t been achieved yet,” Researcher Mustafa Munawar says.  

 

It is important for the researchers to be able to help farmers in their work. Curiosity drives them to uncover the genetic mechanisms behind plant diseases.

“Plant diseases are a major problem, and we need to get them under control,” Toljamo says.  

“Strawberry farmers need expert help, but this is not something we make commercially available through the university. Luckily, farmers can make use of our research findings,” says Munawar, who is mainly interested in innovative molecular biology solutions.

“It’s great that nowadays we can do research all year round, thanks to our LED-illuminated rooms and growth chambers. We are able to work on a continuous basis instead of having to wait for the growing season,” Kokko says.

UEF Bulletin 2018