GLYCOALKALOID CONTENT OF NEWFOUNDLAND GROWN POTATO TUBERS AND POTATO WART TISSUE

Eight cultivars of potato tubers grown in Newfoundland were examined for total glycoalkaloids (TGA) at harvest and after 3, 6, 9 or 12 days exposure to 150 footcandles light. Freshly harvested tubers had TGA ranging from 0.9 to 15.4 mg/100 g of total tuber tissue. TGA increased as a result of long term light exposure in all cases; however, those cultivars surface-pigmented with red or blue anthocyanins were less responsive to light induction. TGA in light exposed tubers ranged from 52–71 mg/100 g for white cultivars, 26–46 mg/100 g for red varieties, and 23–40 mg/100 g for those pigmented with blue anthocyanins. Healthy tubers from plants afflicted with potato wart did not show abnormally high TGA; however, healthy cankers contained as high as 170 mg/100 g. Greening or decomposition of wart tissue was associated with a decline in TGA. Thin-layer chromatography revealed α-solanine and α-chanconine were the principal components in TGA extracts of both tubers and wart tissue.