Variety resistance stops race change challenges in spinach Varietal resistance to spinach downy mildew is now one of the most important selection criteria in variety choice for the UK’s specialist growers, according to Syngenta leafy salad specialist, Rosemary Atwood. The announcement of two new official races of the spinach downy mildew pathogen (Peronospora effusa) this season further increases the challenge for the industry and the focus for breeding programmes. The newly declared race Pe:18 has been found widely across Europe, with the strain Pe:19 predominantly in the US. However, the International Working Group on Peronospora in spinach (IWGP), has declared: ‘both races pose a significant threat to the spinach industry in all parts of the world, and resistance to these new races is important’.