Changes in phenol oxidase and peroxidase levels in cocoyam tubers of different postharvest ages infected by Sclerotium rolfsii sacc.

Crude aqueous extracts from the peripheral rot zone of cocoyam tubers infected by Sclerotium rolfsii sacc were shown to be inhibitory to dialysed in vivo polygalacturonase (PG) of the pathogen. The PG inhibitory action, phenol oxidase and peroxidase activities were higher in cocoyam tubers of the Xanthosoma sagittifolium varieties than in those of the Coolocasia esculenta varieties. The levels of phenol oxidase, peroxidase and PG inhibitory activities also decreased as the postharvest age of the tubers increased.