INFLUENCE OF THE CHANGING CLIMATE ON FLOWER BUD DEVELOPMENT OF APRICOT VARIETIES

One of the most spectacular effects of the warmer climate in Hungarian orchards is the faster bud development and earlier blooming of fruit trees, including apricots. This is extremely unfavourable, because it increases the probability of frost damage. The frost tolerance of organs changes during the winter and the rate of development is dependent on genetic properties and temperature changes. Observations on the flower bud development and blooming time in a number of apricot varieties were begun 10 years ago in the centre of Hungary, which is situated at the crossing point of the Mediterranean, Atlantic and continental climatic zones, causing very fluctuating weather conditions. The data were used to model the effect of changing temperature on phenological processes. Of these 10 years, the winter of 1995-96 was the coldest and that of 1997-98 the mildest. In the coldest winter, very slow flower bud development was observed. The varieties reached the tetrad stage by the second half of March and bloomed in the second half of April. In the mildest winter, the tetrad stage was observed between the 15th of January and the 5th of February, approximately 2 months earlier than in the coldest year. Blooming was also very early, starting in the first few days of March. There was thus a 49-day difference between the blooming time of apricot varieties in these two years. The generative organs of apricot genotypes are very sensitive to climate change, and to mild and fluctuating temperatures, particularly during the ecodormancy period. This fact must not be ignored, to ensure the efficiency of apricot production.