Comparison of the calystegine composition and content of potato sprouts and tubers from Solanum tuberosum group Phureja and Solanum tuberosum group Tuberosum.

The calystegines detected in tubers from 17 Phureja (S. tuberosum Group Phureja) lines and five Tuberosum (S. tuberosum Group Tuberosum) cultivars were identified as the A3 and B2 structural types. Their concentration in whole tubers was of a similar order of magnitude in both species, as was the variability in the ratio of B2 to A3. On average, calystegine concentrations in the peel were about 13 times that found in the flesh for the five Tuberosum cultivars, and 4 times higher for four Phureja lines. Removal of the peel reduced the calystegine content by an average of over 50% in Tuberosum but by only 30% in Phureja, despite the latter having the greater proportion of peel. The calystegine content of sprouts was also determined for five Tuberosum cultivars and four Phureja lines and was found to include small amounts of four additional types, B3, B4, N1, and X2, in addition to the more abundant A3 and B2. Concentrations in the sprouts of Tuberosum were on average 100 times higher than that in the tuber flesh and 8 times higher than in the peel, whereas for Phureja, the equivalent values were 30 and 7 times higher, respectively. No correlation was found between sprout concentration and either flesh or peel calystegine concentration.