Abstract
Jack bean (Canavalia ensiformis) and French bean (Phaseolus vulgaris) cv. The Prince were useful diagnostic hosts for broad bean stain virus and Echtes Ackerbohnenmosaik-Virus. Bottom and middle component of each virus complemented one another to give greatly increased infectivity but there was no complementation between components from the different viruses. Bottom and middle components of each virus were indistinguishable serologically.