Method Validation by Ringtesting to Establish International Standards for Seed Testing; a Case Study

The International Seed Health Initiative - Herbage Crops (ISHI-H) has initiated ringtesting to establish international standards for the detection of Clavibacter michiganensis subsp. insidiosus, the causal pathogen of bacterial wilt in lucerne-alfalfa [Medicago sativa) seed. Bacterial wilt of lucerne is a seedborne disease causing wilting, stunting and yellowing of plants. In the field disease symptoms are not severe until the second or third year when significant yield loss can occur. The bacterium can survive in the field for 8–10 years. Because infected seed is a possible source of international spread, phytosanitary regulations are in place in many importing countries. Currently there is no internationally accepted seed test for bacterial wilt.