In vitro screening of cold resistant strawberry cultivars and seedlings

Cold resistance of plants and proliferating structures in vitro have been studied within nine strawberry cultivars and seedlings of 4 combinations. Cultivars, known for their characters, were used as model in order to identify the possibilities for selection of cold-resistant seedlings in vitro. Microplants and proliferating structures were hardened for maximum 35 days at 2+/-0.5 degrees C, frozen for 1-8 days at -8 degrees C, -9 degrees C, -10 degrees C, -11 degrees C, -12 degrees C, -14 degrees C in vitro in the media Murashige and Skoog with 1.5, 3, 6 or 9% sucrose. Explants were thawed at 2+/-0.5 degrees C for 1-3 days. The degree of cold injury was evaluated according to 6-point scale (0-5). The best temperatures for freezing in vitro for differentiation of cultivars for cold resistance were -9 degrees C to -11 degrees C. Explants were more viable, whem time of hardening was longer. Viability of plants also depends on sucrose amount in the media.