New Race Of Downy Mildew In Spinach Named Pfs: 16

A new race of the downy mildew pathogen (Peronospora farinosa f. sp. spinaciae = P. effusa) on spinach was first identified in March 2015 in Salinas, CA. This race was able to overcome most of the race 1-15 varieties evaluated.

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The isolate, originally designated UA201519B, was characterized based on disease development on a standard set of differential varieties. Subsequently, isolates with the same reaction pattern on the differential set have been found in numerous locations, according to a press release from Plantum, the Dutch association for the plant reproduction material sector.

After careful evaluation of the significance of this development to the spinach industry, the International Working Group on Peronospora (IWGP) has named isolate UA201519B race Pfs: 16.

Race Pfs: 16 is able to infect the differential cultivars ‘Viroflay,’ ‘Resistoflay,’ ‘Clermont,’ ‘Lazio,’ ‘Pigeon,’ and ‘Meerkat,’ but not able to infect ‘Califlay,’ ‘Campania,’ ‘Boeing’ (‘Avenger’), ‘Lion,’ ‘Whale,’ and ‘Caladonia.’ The IWGP is continuously monitoring the appearance of strains of the pathogen that deviate in virulence from the known races.

The group aims to promote a consistent and clear communication between 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.

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Located in The Netherlands, the IWGP is is administered by Plantum. The organization consists of spinach seed company representatives (Pop Vriend, Monsanto, Rijk Zwaan, Bayer, Takii, Sakata, Bejo, Enza, Syngenta, and Advanseed) and Naktuinbouw, and is supported by research centers at the University of Arkansas and the University of California Cooperative Extension (Monterey County) in the U.S.

Researchers all over the world are invited to join the IWGP initiative and use the common host differential set to identify new isolates.

 

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