Long-term investigation results of low temperatures influence on apricot generative buds

Short rest period of generative buds in apricot trees causes their significant damages or total loss during winter temperature fluctuations or spring frosts. Adapting to the environment is one of the main reasons for the limited apricot introduction in different climatic zones. To solve this problem we have been investigating frost resistance of generative buds in 40 apricot cultivars and forms of different origin for 34 years by the method of artificial freezing of branches in a cooling chamber. This method allows assessing cultivars under the influence of different temperatures (from-6.5 to-24 degrees C) considering their morphogenesis that increases effectiveness of the research. 23 cultivars and breeding forms have been identified ('Semlak, `Da-Huang-Hou, '84-951, '84-952' and others) with the smallest damage of buds (0-13.5%) at the early stages of morphogenesis (sporogenous tissue or microsporocytes initiation). These genotypes are characterized with slow development that enables them to better retain the negative impact of freezing temperatures. In some cultivars buds retain their relatively high frost resistance also at the later stages of morphogenesis (microspore tetrads formation and disintegration, one-celled pollen grains formation, etc.). 8 genotypes with the highest number of undamaged buds (71.0-79.0%) were identified. Among them 5 cultivars and forms pa-Huang-Hou, 'Ladoga, 'Perekopsky 8 1/12, `Seedling Karakalinskogo, and 7apozdalyil are characterized with frost resistance of generative buds both at the later stages of development and at early ones. Thus, the results of long-term researches let to conclude the possibility of selection of genotypes with high adaptive potential selection and to demonstrate the dependence of adaptation mechanism on the rates of morphogenesis.