DETECTION AND IDENTIFICATION OF FLUORESCENT COMPOUNDS IN POTATO-TUBERTISSUE WITH CORKY PATCH SYNDROME

A corky patch syndrome that effects potato tuber tissue may be a later manifestation of pink eye disease of potato although an actual cause and effect relationship between the two diseases has not been firmly e stablished. The causal agent for pink eye of potato is unknown but the disease has been associated with the fungi Verticillium and Rhizocton ia and the bacterium Pseudomonal fluorescens. Pink eye and corky patch symptoms on the periderm of affected tubers are accompanied by a band of tissue beneath that is intensely auto-fluorescent when viewed unde r ultraviolet illumination. Studies to determine the cause of the fluo rescent reaction were performed using HPLC and a fluorescence monitor. Three phenylpropanoid compounds, chlorogenic acid, esculin and scopol etin, were found to be involved. It appears that these compounds are p roduced by tuber tissues in response to pathogen invasion and also as part of the wound healing process. Tissues with corky patch syndrome, silver scurf and root-knot nematode contained high concentrations of c hlorogenic acid and esculin and low concentrations of scopoletin. Tiss ues infected with dry rot were visibly less fluorescent, and contained less chlorogenic acid and esculin, and no detectable level of scopole tin.