Isolates sometimes have to be characterised based on a set of varieties with a well-described resistance. This may be necessary to validate a resistance test or to identify an unknown isolate. This set is indicated as a differential set. A list of differential sets used in resistance breeding can be found at the website of the International Seed Federation.
Seeds of some differential sets are available through Naktuinbouw for any organisation that has an interest and is involved in harmonising resistance tests, or to monitor how a pathogen evolves. The differentials are multiplied by partners of Naktuinbouw. Seeds of differentials are supplied free of charge.
Naktuinbouw can supply seeds of the following differential sets:
For lettuce: Bremia lactucae
For spinach: Peronospora farinosa f. sp. spinaciae
For cabbage: Plasmodiophora brassicae