Results from 13-year study of cultivar-rootstock combinations in sweet cherry

The study was carried out during the period 1999-2011 at the Institute of Agriculture - Kyustendil, Bulgaria. The growth, reproductive characteristics and fruit quality of 'Van' sweet cherry trees, grafted on clonal rootstocks: 'P-7', 'Karamy', 'Hybrid 2', 'SL-64' and seedlings from 'Vladimir' and 'Mahaleb 20-86' were studied. The trees on 'SL-64' were used as a control. The trees were planted in the spring of 1999 at distances of 5.50×5.0 m, formed in free-growing crowns and grown without irrigation. After thirteen years, the biggest trunk cross-sectional area had the trees grafted on 'Hybrid 2' and the smallest on 'Mahaleb 20-86'. The trees crown volume was reduced by 14.9% for 'Vladimir', 21.4% for 'P-7', 22.6% for 'Hybrid 2', 27.8% for 'Mahaleb 20-86', and 35.9% for 'Karamy', when compared to 'SL-64'. The row strips were not occupied by the trees, which allow optimizing planting distances. 'P-7' had the highest root-suckering ability, followed by 'Vladimir'. Trees grafted on 'Vladimir' had the best vitality, while those on 'Karamy' were with the highest mortality rate. The highest productivity had the trees on 'SL-64' and the lowest on 'Karamy'. Productivity was also good for 'P-7' and 'Vladimir', which was confirmed by the data for yield efficiency and the quantity of fruit 1 m^-3 of the crown volume. No significant differences were found in the average weight and fruit size as well as in their chemical composition (dry matter, total sugars and acids) among tested rootstocks.