Accumulation of hydroxycoumarins during post-harvest deterioration of tuberous roots of Cassava (Manihot esculenta Crantz)

The use of the root crop Cassava (Manihot esculenta Crantz) is constrained by its rapid deterioration after harvest. Chemical and spectroscopic examin ation revealed the accumulation of four hydroxycoumarins (esculin, esculeti n. scopolin and scopoletin), compounds derived from the phenylpropanoid pat hway, during the time course of post-harvest deterioration. Fluorescence-mi croscopy revealed their localization in the apoplast of the parenchyma. Sco poletin and scopolin showed the most dramatic increases in concentration, p eaking by day 2 after harvesting. A smaller secondary peak of scopoletin te nded to be more pronounced in cultivars showing lower susceptibility to det erioration. Evidence for the metabolism of scopoletin to an insoluble colou red product by means of a peroxidase is presented. This product may be the cause of the discolouration of the vascular tissue during storage. (C) 2000 Annals of Botany Company.