Soon it will be possible to grow strawberries that withstand frost. This will lengthen their growing season in countries that must cope with cooler climates.

Strawberries are sensitive to cold. Each year, at least 20 per cent of the annual strawberry crop in countries such as Norway is lost due to frost.

Norwegian researchers are working to identify and understand the genes associated with frost tolerance in strawberries. The objective is to strengthen the plants’ immunity to frost.

“We are searching for strawberry varieties that can withstand frost and still score high for important characteristics such as taste, colour and firmness,” explains Muath Alsheikh, a researcher and strawberry breeder at Graminor AS, Norway’s national plant-breeding company.

New varieties in response to climate change

Developing new cultivars (bred plant varieties) adapted to the chilly growing conditions of the north has long been a priority of Norway’s agriculture industry. Prospective changes to the climate make it even more essential to breed new, hardier plant varieties that can withstand harsher growing conditions.

In recent years, advances in molecular genetics have expanded the range of tools available to plant breeders.

“New technology enables us to develop frost-resistant cultivars much more quickly than we can using conventional methods,” says Idun Christie, CEO of Graminor.

In collaboration with Norwegian and international players, the company is carrying out research using molecular techniques to solve the frost challenge. The projects receive funding from the Food Programme: Norwegian Food from Sea and Land under the Research Council of Norway.

Competitive international advantage

Graminor’s task is to ensure that Norwegian farmers and horticulturists have access to a diversity of disease-free plant materials suitable for Norwegian growing conditions.

“We carry out tests on good seed products or varieties from outside of Norway under Norwegian conditions,” says CEO Christie. “Currently, Norwegian farmers cultivate mostly international strawberry varieties – but these tend to be poorly suited to the winter demands of our climate. Developing new varieties can yield substantial benefits within Norway, and will have potential in the international market as well.”

Efficient new methods

It is very time-consuming to breed new strawberry varieties, particularly frost-resistant ones, using conventional methods. Each year, Graminor breeds hybrids that yield roughly 5 000 seed-producing plants . After a decade of testing and evaluation, one or maybe two of these might be approved as new varieties.

Using methods based on molecular markers, however, scientists can now more rapidly identify the genes associated with frost tolerance. Such markers are used in molecular genetics to identify a specific sequence of DNA or proteins that show heritable variation.

The researchers analyse various strawberry varieties under controlled cold-temperature trials in the laboratory to pinpoint the relevant markers. They have found a clear correlation between frost resistance and amount of proteins in the plants. Other DNA markers also play a role in a variety’s ability to withstand frost.

“The knowledge we obtain will make it possible to select frost-tolerant strawberries quickly and efficiently,” summarises Muath Alsheikh.

Benefits other berries, too

“This is research that is applicable for strawberry farmers working in frost-prone climates all over the world, for instance in all the Nordic countries,” adds Ms Christie, “so we are coordinating our efforts with other Nordic research groups. We hope that this new methodology for breeding winter hardiness in strawberries can also be applied to other kinds of berries that have difficulty surviving the winter.”

“Adapted plant material is critical for profitability in any plant production,” states Kirsti Anker-Nilssen, Adviser in the Food Programme. “The expected changes in winter climate ahead will make good winter hardiness and frost tolerance all the more important.”