Cold Resistance in Root and Cane of Own-root 'Kyoho' Grapevines

Root and cane of own-root 'Kyoho' grapevunes were tested for winter cold resistance using EC(electrical conductivity) and TTC(triphenyl tetrazorium chloride) tests, as well as anatomical observations and survival tests. Vines were exposed to various subzero temperatures for various durations in two separate experimental trials, one in December, one in January. The EC and TTC reduction of small roots (φ3-5mm)were slightly affected. After exposure to -4℃ for only 12 hours the EC markedly increased and TTC reduction decreased in both small and large roots. Cells of cortex and ray tissues in the root were ruptured. New root growth on root cuttings taken from the vine previously exposed to -4℃ was servely inhibited. These results indicate that 'Kyoho' roots cannot resist temperatures of -4℃ or lower even for a single night during winter. On the other hand, 'Kyoho' canes survived -15℃ even for 24 days. However, exposure to -20℃ or -30℃ greatly affected the EC and TTC reduction in the cane and inhibited bud bursting entirely.