THE INFLUENCE OF TEMPERATURE ON LIGHT ENHANCED GLYCOALKALOID SYNTHESIS IN POTATO

The influence of temperature on total glycoalkaloid (TGA) synthesis in tubers exposed to light (250, mumol m-2 s-2 PAR, Photosynthetically A ctive Radiation) or dark environments for 96 h was examined in three p otato cultivars. Following 96 h light or dark the tubers were stored w ithout light at 5-degrees-C or 24-degrees-C and TGA concentrations mon itored over the subsequent 30 and 90 days. Exposure to light and culti var were found to be major factors influencing TGA concentrations; tem perature had no significant effect. TGA content in illuminated tubers of cvs 'Pentland Hawk' and 'Kerrs Pink' were significantly higher (P < 0.01) compared with tubers placed in the dark. TGA concentrations in cv. 'Desiree' increased significantly only following exposure to light at low temperatures (P < 0.05). Removal of tubers from storage at 5-d egrees-C and immediate illumination at 24-degrees-C altered the ratio of glycoalkaloids in cvs 'Pentland Hawk' and 'Kerrs Pink'. Regardless of cultivar and storage temperature TGA concentrations were higher at the end of the storage period compared with initial TGA concentrations . During storage TGA concentrations fluctuated widely and gradual accu mulation of glycoalkaloids with time was rarely demonstrated except in cv. 'Desiree'. Tubers stored at 24-degrees-C accumulated higher TGA c oncentrations than those stored at 5-degrees-C in cv. 'Kerrs Pink' but not in cvs 'Pentland Hawk' and 'Desiree'. Tubers of cv. 'Kerrs Pink' exposed to light prior to storage accumulated glycoalkaloids more rapi dly than unexposed tubers during storage at 24-degrees-C and occasiona lly at 5-degrees-C. Light enhanced glycoalkaloids are not degraded ove r time.