11 May 2018

Denomination of a new official race of downy mildew in spinach

With effect from 26 April 2018, the International Working Group Perenospora in Spinach (IWGP) has named a new official strain of spinach downy mildew, Pfs:17

New official mildew strain

A new race of the downy mildew pathogen (Peronospora farinosa f. sp. spinaciae = P. effusa) on spinach was first identified in 2014 in Yuma, Arizona, U.S. This race was able to overcome the resistance of important spinach varieties.


Located in the Netherlands and administered by Plantum, the IWGP consists of representatives from major international seed companies, Naktuinbouw and various research centres.

The IWGP continuously monitors the appearance of new strains of the pathogen, and promotes clear and consistent communication of resistance breaking races of mildew. Using common differential sets IWGP members monitor outbreaks of mildew, and the appearance of new isolates.

More details can be found in an announcement on the website of Plantum, or in the downloadable press release below. 

Integrated resistance management

Rijk Zwaan’s spinach program has a range of varieties resistant to Pfs:17, other official strains, and in some cases to other local isolates. For the most up to date information on varietal performance and mildew, we recommend that growers speak to their local sales representative.

Rijk Zwaan advocates 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.


Download the Plantum Press Release