EFFECTS OF METEOROLOGICAL VARIABLES ON FREE AND SELF-FERTILITY OF SOUR CHERRY

We conducted an analysis of fruit set of sour cherry flowers over a 22-year period and correlated fruit set data to meteorological variables. Our analysis showed that the degree of free fertilization (combination of cross- and self-pollination) was mostly influenced by maximum temperature and sunshine duration. The rate of free fertilization increased with higher daily maximum temperatures and longer sunshine duration. The effectiveness of self-pollination significantly depended on the meteorological conditions. Degree of self-fertilization was influenced directly by temperature and indirectly by other climatic parameters. There was a significant connection between maximum and minimum temperatures during bloom and the rate of self-fertilization. Increases of maximum temperature reduced the effectiveness of self-pollination. A 1°C increase of maximum temperature reduced self-fertilization rate by 0.6%. When considering minimum temperature, the most favorable temperature was 7.5-8.5°C. If minimum temperatures were under 4°C or above 12°C, self-fertilization rate was reduced to a quarter of the value at 8°C. We believe that the effectiveness of self-fertilization can be improved considerably by placement of isolator bags within the canopy of the tree, avoiding placement on the external, western canopy surface.