Denomination of New Official Downy Mildew Race in Lettuce for Western US

Downy mildew can affect lettuce leaves in both protected and open-field crops, resulting in a loss of yield. A new variant of downy mildew (Bremia lactucae or Bl) has been found in California. This race has received the denomination Bl: 10US.

IBEB-US reports that the race has already become widespread and has been present for over a year. The good news is that Rijk Zwaan already has varieties with resistance against Bremia-races BI: 7 to 10US. Rijk Zwaan's crop specialists are happy to advise growers with detailed information about the company's range of lettuce varieties and their resistances against Bremia and other diseases.

Over 500 lettuce varieties have been developed at Rijk Zwaan’s research and breeding station in the Netherlands and the trial station in California, tailored to diverse cultivation methods and environmental conditions and with various resistances.

Sustainable solutions

Rijk Zwaan focuses heavily on resistance breeding to make plants resilient against diseases such as downy mildew. Rijk Zwaan strongly advocates for integrated pest and disease management to minimize the risk of plant disease outbreaks. While resistant varieties play a crucial role, the company also recommends the restrained use of appropriate crop protection agents to prevent the development of new downy mildew variants. Additionally, practicing good hygiene, such as removing diseased plants and promptly plowing crop residues into the soil, can help reduce the spread of downy mildew in lettuce.

International Bremia Evaluation Board

The International Bremia Evaluation Board (IBEB) is a joint initiative of lettuce breeding companies in the USA, France and the Netherlands, as well as the University of California-Davis, the Netherlands’ Inspection Service for Horticulture (Naktuinbouw) and the French National Seed Station (GEVES). IBEB’s mission is to identify new races of Bremia lactucae that pose a significant threat to North American or European lettuce production and to promote the use of standardized race names in communication with growers.

Races are identified and denominated by regional IBEB committees specifically for each continent.