Johan Schut breeding manager lettuce Rijk Zwaan

Johan Schut, breeding manager lettuce at Rijk Zwaan

Rijk Zwaan has highlighted the resistance of its lettuce range to downy mildew, on the day a new variant was officially named.

The International Bremia Evaluation Board Europe (IBEB-EU) has today (1 June) denominated the new variant of downy mildew as Bl:37EU.

The variant was identified last year, having been found in multiple regions in France and, more recently, in Spain, Portugal and Italy.

Downy mildew is a major threat in lettuce. The fungus can damage the lettuce leaves in both protected and open-field crops, resulting in a loss of yield.

The IBEB-EU said that the new Bl:37EU race was expected to spread further in the summer and autumn this year, although it was currently “difficult to predict” which areas would be affected.

Resistant varieties

According to vegetable breeding specialist Rijk Zwaan, most of its current lettuce varieties are resistant to the new race of downy mildew.

Johan Schut, breeding manager lettuce at Rijk Zwaan, said that the development of resistances against downy mildew was one of the pillars of lettuce development programme.

“Downy mildew is evolving genetically all the time and a large number of isolates of the plant fungus are already known worldwide,” Schut explained. “In our breeding programme we are continuously working on improving the traits of our lettuce varieties, including resistances to new downy mildew variants.

“The large majority of Rijk Zwaan’s current lettuce varieties are resistant to the new Bl:37EU race of downy mildew,” he added.

Sustainable solution

Rijk Zwaan stated that it was a strong advocate of an integral approach to combating plant diseases in order to reduce the use of chemicals.

Although resistant varieties play an important role in this, the company said that it also advised crop protection agents and hygiene measures to prevent new downy mildew variants from developing.

Good hygiene practices such as burying crop residues and promptly removing diseased plants help to limit the spread of downy mildew in lettuce, Rijk Zwaan confirmed.