Necrotic Stunt Disease of Konjak, Amorphophallus konjac, Caused by Cucumber Mosaic Virus

Konjak (Amorphophallus konjac) plants showing necrosis in leaflets and stunting of petiole have been found in Gunma Prefecture since around 1960. The causal virus was transmissible by aphids and by mechanical inoculation, but not through corms and cormlets of konjak. The virus was identified to be cucumber mosaic virus (CMV) by immunodiffusion tests. Five CMV isolates obtained from different konjak fields were compared serologically, and three of them were indistinguishable from CMV-Y whereas the other two were identical to CMV-P. All these isolates caused similar symptoms on konjak plants to those observed in the fields. We propose the name of the disease, konjak necrotic stunt disease.