10 May 2017

New Race of Downy Mildew in Lettuce Bl:33EU

New race of downy mildew in lettuce: Bl:33EU


The International Bremia Evaluation Board (IBEB) has officially designated a new race of downy mildew in lettuce: Bl:33EU.

In November 2016, the IBEB met in Paris to evaluate the Bremia lactucae isolates found in Europe in 2016. Once again, many outbreaks of Bremia were caused by new Bremia races with only local importance. However, one race spread in most European counties and IBEB-EU decided to denominate this isolate as the new race Bl: 33EU. Bl: 33EU is widely spread in France and was also found in Germany, the Netherlands, United Kingdom, Scandinavia and Belgium. Until now it has not spread to South European countries.

New notation
A new element added to the Bremia race code is the suffix to distinguish EU and US races, referring the distinct populations in Europe (EU) and America (US). As of 1 September 2017, all official European races will be indicated with a suffix –EU. Californian races will be indicated by Bl: and suffix –US. Detailed studies did not show long distance spread of Bremia-isolates between the two continents. Therefore, the denomination of European and American isolates is performed by two separate, closely collaborating working groups, IBEB-EU and IBEB-US.

Wide range with resistance
Rijk Zwaan has a wide range of lettuce varieties available with resistance against Bl:33EU. We are pleased that clarity has been provided about the mildew race. Now that it has officially been recognised, Rijk Zwaan can once again inform its customers clearly and fully about the resistance patterns of its varieties. To get a complete overview of Rijk Zwaan lettuce varieties and their resistance patterns, it’s best to contact a Rijk Zwaan crop advisor. Please contact Braden Hoover. b.hoover@rijkzwaan.com