Effect of storage temperature on potato (Solanum tuberosum L) tuber glycoalkaloid content and the subsequent accumulation of glycoalkaloids and chlorophyll in response to light exposure

Tubers from six potato cultivars were placed into either 10 or 4 degrees C stores immediately postharvest. Replicated tuber samples were analyzed for glycoalkaloid (TGA) content immediately postharvest, after 6 and 14 weeks s torage at 10 degrees C and after 6 weeks storage at 4 degrees C. Subsamples from the 10 degrees C store were removed after 1, 2, 3, 4, and 8 weeks, re spectively, stored for a further 6 weeks at 4 degrees C, and again analyzed for TGA content. After each sampling date, tubers were exposed for 96 h to light and analyzed for both chlorophyll and TGA concentrations. The result s indicated that the exposure of tubers from some cultivars, such as Brodic k and Pentland Crown, to low temperatures within 2 weeks of harvest resulte d in a relatively rapid accumulation of glycoalkaloids to levels close to o r exceeding the recommended safe maximum level of 200 mg of TGA per kilogra m of fresh weight, while other cultivars, such as Eden and Torridon, appear ed insensitive to cold stress. Storage for 6 weeks at both 10 and 4 degrees C resulted in a greater accumulation of glycoalkaloids in response to ligh t exposure relative to that observed immediately postharvest, with the tube rs from all six cultivars stored at 4 degrees C producing over twice the am ount of TGA as those stored at 10 degrees C. Storage at 10 degrees C prior to 6 weeks storage at 4 degrees C resulted in smaller photoinduced increase s in TG;A content but even after 8 weeks at 10 degrees C followed by 6 week s at 4 degrees C, the photoinduced increases in all cultivars were signific antly higher than that recorded for tubers stored continually at 10 degrees C, which had values comparable to those obtained immediately postharvest; In all cultivars photoinduced chlorophyll accumulation was little affected by storage temperature but was slightly, although significantly, reduced as time in storage increased from 6 to 14 weeks. The significance of these re sults in relation to consumer safety and plant breeding are discussed.