Differences of In Vitro Thermotolerance to High Temperatures in Autochthonous Sweet Cherry Varieties from the Jerte Valley (Spain)

Different clones of the autochthonous sweet cherry varieties 'Ambrunes', 'Pico Negro' and 'Pico Colorado' from the 'Clonal Selection Program' were subjected to different temperature regimes to optimize in vitro heat therapy to obtain virus-free plants. These varieties were especially sensitive to high temperature treatments: 'Ambrunes and 'Pico Colorado' had similar thermotolerance, and 'Pico Negro' was less tolerant. However, one of the 'Pico Negro' clones had similar thermotolerance to 'Ambrunes' and 'Pico Colorado'. It is necessary to establish a period of adaptation to high temperatures for increasing both the plant and the isolated apex survival.