Fungal Pathogens of Wasabi in British Columbia

Wasabi (Wasabia japonica L.) is a high-value crop in British Columbia and is cultivated in greenhouses where diseases cause economic losses and insect pest issues are emerging. A review of the current literature on wasabi reveals a lack of information on wasabi pest and disease management, especially in North America. The objective of this research was to identify current diseases affecting wasabi in BC isolates from plants showing symptoms of leaf blight, leaf spot, and white blister rust were identified by molecular and morphological methods. Results revealed that Botrytis cinerea, Collectotrichum higginsianum, and Albugo candida were present. Inoculation studies showed B. cinerea was weakly pathogenic, while C. higginsianum caused lesions on wasabi and Brassica juncea, but not on alfalfa (Medicago sativa). In culture, fastest growth of C. higginsianum occurred at 25 and 30°C, and the highest conidial production occurred under continuous darkness. Isolates of A. candida from shepherd’s purse (Capsella bursa-pastoris) plants were identical to those from wasabi, suggesting a source of inoculum. Disease control in an integrated pest management system will remain an important aspect of mitigating economic losses.