Abstract
An undescribed disease of giant onion (Allium giganteum Regel) was observed in Miyagi Prefecture in 1999. Disease symptoms appeared mainly on leaves and sheaths, and these symptoms were elliptical brown to purple lesions, becoming zonate with the development of the disease. Pathogenicity to the host plant was demonstrated by the inoculation of a fungus isolated from a diseased plant. The fungus was identified as Alternaria porri on the basis of morphological and cultural characteristics. To our knowledge, this is the first report on the occurrence of purple blotch in giant onion in Japan.
