Metabolites accumulating in potato tubers following infection and stress.

Abstract

AbstractA broad spectrum of secondary plant metabolites are found in healthy, infected, and stressed potato tuber tissue. These include: chlorogenic, caffeic, vanillic, p‐hydroxybenzoic, and salicylic acids, scopolin, scopoletin, α‐solanine, α‐chaconine, solanidine, α‐solarnarine, β‐solamarine, rishitin, rishitinol, phytuberin, and lubimin. Infection and stress qualitatively and quantitatively influence these constituents. Chlorogenic and caffeic acids, scopolin, scopoletin, α‐solanine, α‐chaconine, and solanidine rapidly accumulate in injured tubers at or close to the sites of injury. In the 22 cultivars of potato studied α‐ and β‐solamarine were only found to accumulate in foliage or injured tubers of the cultivar Kennebec. Infection of tubers with Phytophthora infestans, the incitant of late blight, or a number of other fungi and bacteria causes accumulation at the site of infection of chlorogenic and caffeic acids, scopolin and scopoletin, rishitin, rishitinol, phytuberin, and at times lubimin. These compounds accumulate at levels that are fungitoxic and they appear part of the mechanism of disease resistance of the potato tuber. Resistant tubers infected with P. infestans accumulate more than 200 times the rishitin and related terpenoids found in uninfected tubers. Chlorogenic acid and caffeic acid, scopolin, scopoletin, α‐solanine, α‐chaconine, and solanidine are normal constituents of potato peel, and their concentration in the peel can be equal to that in injured peeled tubers. Freshly peeled healthy tubers contain little or none of the compounds. The danger of introducing substances potentially toxic to humans into food crops is suggested by tne occurrence of α‐ and β‐solamarine in aged tuber slices of the cultivar Kennebec. These substances might arise from the use of mutants or crosses with wild inedible species in breeding programs.