16 Apr 2021

Denomination of Pe: 18 and 19, two new races of downy mildew in spinach

Two new races of the downy mildew pathogen (Peronospora effusa) on spinach have been denominated by the International Working Group on Peronospora in spinach (IWGP). Isolate SP1924 found in Europe, is denominated as race Pe: 18. Isolate UA202001E, found in the USA, is denominated as race Pe: 19. Rijk Zwaan’s spinach program has already a selection of varieties resistant to Pe: 18 and Pe: 19.

Both races pose a significant threat to the spinach industry in all parts of the world and resistance to these new races is important. “As vegetable breeding company, we are pleased to be able to offer a solution to spinach growers worldwide with resistant spinach varieties,” said Rijk Zwaan’s Product Co-ordinator Breeding Terra and member of the International Working Group on Peronospora (IWGP), Anne Königs. 

Rijk Zwaan’s resistant spinach varieties

Rijk Zwaan’s spinach program already has a selection of varieties resistant to Pe: 18 and Pe: 19, as well as other official strains and in some cases, to other local isolates. For the most up-to-date information on varietal performance and mildew resistances, we recommend that growers speak to their local sales representative.

Integrated resistance management

Rijk Zwaan advocates for an integrated approach to resistance management. Resistant varieties are a large part of this, but disease controls and hygiene measures are also important to help prevent the development of new mildew races. Proper hygiene practices, such as removal of debris and diseased plants, will reduce the spread of mildew in crops.

About IWGP

The International Working Group on Peronospora in spinach (IWGP) is continuously monitoring the appearance of strains of the pathogen that deviate in virulence from the known races. In this way the IWGP aims to promote consistent and clear communication between the public and private entities such as the seed industry, growers, scientists, and other interested parties, about all resistance-breaking races that are persistent enough to survive over several years, occur in a wide area, and cause a significant economic impact. 

More details can be found in the downloadable press release on our international Rijk Zwaan website

Sector collaboration

The IWGP is operating internationally and is administered by Plantum located in The Netherlands. The IWGP consists of representatives from spinach seed companies (BASF, Bayer, Bejo, DeSeed, Enza, Pop Vriend, Rijk Zwaan, Sakata, Syngenta, Takii, and Vilmorin) and Naktuinbouw, and is supported by public research at the University of Arkansas. Spinach researchers over the world are invited to join the IWGP initiative and use the common host differential set to identify new isolates. All denominated isolates and seeds of the differential set are available at Naktuinbouw (The Netherlands) and the International Seed Federation