Gouda, The Netherlands
March 1, 2016
The International Bremia Evaluation Board-Europe (IBEB-EU) has evaluated all Bremia isolates recently collected from lettuce fields in Europe. The Bremia pressure was relatively low in 2015. There were serious outbreaks, sometimes caused by new strains, but none of these new strains gained more than local importance. Therefore, IBEB-EU decided not to denominate a new race. The Board emphasizes the importance of chemical control and hygiene measures in addition to the use of resistant varieties to prevent the development of new races.
In November 2015, the European partners of the International Bremia Evaluation Board (IBEB-EU) met in Paris, France, to evaluate the Bremia lactucae isolates found in Europe in 2015. A total of 250 isolates were evaluated. Twenty percent of the isolates were recognized as known and already denominated Bremia lactucae (Bl:) races. Bl: 29 occurs all over Europe, Bl: 30 was also found in various regions. Bl: 31 and Bl: 32 were also found, but less frequently.
The board notices that, more often than in the past, some Bremia strains can cause serious damage locally without spreading quickly to other growing regions. Often, these strains will not survive over years. Therefore, it is decided not to denominate them yet. The trend towards greater diversity of Bremia isolates may be related to the increasingly wide range of resistance genes in many new and successful lettuce varieties, and to other integrated crop protection practices.
The board emphasizes that, although breeding companies supply growers with lettuce varieties possessing resistance to Bl: 16-32, this is not a full insurance against Bremia. Chemical control and hygiene measures are important, in addition to the use of plant resistance, even for varieties with resistance to all denominated Bremia races (Bl: 16-32). Fungicide application, especially in a young plant stage, gives additional protection to resistant lettuce crops. Proper hygiene practices, such as removal of debris and diseased plants, will also reduce the spread of Bremia in lettuce crops. Integrated crop protection will help prevent the development of new Bremia races.
Seeds of IBEB’s shared set of differentials and the reference isolates of Bremia races can be obtained at GEVES/SNES (France) and at Naktuinbouw (The Netherlands). A new, updated and streamlined set EU-C will be available from 1 April 2016. More information about the new set of differentials is provided on the IBEB webpage hosted by ISF (http://www.worldseed.org/our-work/plant-health/other-initiatives/ibeb/)
IBEB-EU consists of representatives of the Dutch and French seed business associations Plantum and UFS, and the organisations of GEVES and Naktuinbouw. IBEB-EU is supported by several Bremia investigators across Europe. The business associations were represented by lettuce breeders of Agrisemen, Enza Zaden, Gautier, Bayer CropScience Vegetable Seeds, Rijk Zwaan, Monsanto Seminis, Syngenta and Vilmorin.
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