Changes in invertase, sucrose-6-phosphate synthase and UDP-glucose pyrophosphorylase activities, and their relations to reducing sugar content in Japanese processing potato varieties stored at low temperature

Invertase, sucrose-6-phosphate synthase (SPS) and UDP-glucose pyrophosphorylase (UGPase) activities of three Japanese processing varieties, differing in susceptibility to low temperature sweetening (susceptibile : Norin-1; middle : Toyoshiro; resistant : Hokkai-82), were measured at intervals during storage at 7°C in order to investigate the role of the three enzyme activities in reducing sugar accumulation during storage. The susceptible variety dramatically increased the reducing sugar content, and invertase, SPS and UGPase activities during storage, whereas the mid-susceptible and resistant varieties progressively increased them. In the three enzymes, both invertase and SPS activities correlated significantly (p<0.01) with the reducing sugar content, implying that invertase and SPS may play an important role in the regulation of the reducing sugar accumulation of processing potatoes stored at low temperature. This information may be useful for potato breeders to develop new resistant processing varieties.