The major glycoalkaloids, a-solanine and a-chaconine, in potato tubers were determined by LC/ESI-MS. The average recoveries from spiked samples by the method used in this study were more than 94% with RSD of analytical values less than 5% for both oe-solanine and a-chaconine. The total glycoalkaloid contents in tubers of four potato cultivars distributed in Japan, cv. Irish Cobbler, Touya, May Queen, and Sayaka, were compared. There was no significant difference in glycoalkaloid content between

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... immature and mature tubers among all the cultivars tested. There was also no significant difference among cultivars in glycoalkaloid content at either the immature or mature stage, except for May Queen, which had higher glycoalkaloid contents at both stages. Glycoalkaloid content increased significantly in cv. May Queen and Touya with 7 days of light exposure immediately after harvest. The light exposure increased glycoalkaloid content in the long-term stored tubers of all four cultivars tested and that in the short-term stored tubers, except for Sayaka.