APPLICABILITY OF IMPEDANCE MEASURING METHOD TO THE DETECTION OF IRRADIATION TREATMENT OF POTATOES

The incubation condition of potato tubers prior to impedance measureme nt greatly influenced the reliability of detection of irradiated potat oes ; the impedance ratio at 5kHz to 50kHz (Z5k/Z50k) determined at 22 -degrees-C at an apical region of tuber which was pre-incubated at 22- degrees-C for 3 days or longer resulted in the best detection of radia tion treatment of potatoes, The impedance ratio was dependent upon dos e applied to potato tubers. Potatoes irradiated at 100 Gy could be dis tinguished from unirradiated potatoes for 10 cultivars of potatoes. Th e impedance ratio of potatoes irradiated at the same dose was little i nfluenced by the planting locality if the cultivar was the same, altho ugh the ratio varied with potato cultivars. These results indicate tha t irradiated potatoes can be detected if the potato cultivar is known. Potatoes 'Danshaku' commercially irradiated at the Shihiro Potato Irr adiation Center could be differentiated from unirradiated 'Danshaku' a t different planting localities ; the impedance ratio was lower than 2 .75 for the unirradiated potatoes and higher than 2.75 for the irradia ted ones.