PERFORMANCE OF THE SWEET CHERRY CULTIVARS 'VAN' AND 'KOZERSKA' ON CLONAL ROOTSTOCKS

A trial with ‘Van’ and ‘Kozerska’ sweet cherry cultivars, grafted on vegetative rootstocks Gisela 3, Gisela 5, Gisela 6 and Weiroot 10, was established in the spring of 2006 at the Institute of Agriculture - Kyustendil, Bulgaria. The trees were planted at distances of 4.0×2.5 m, shaped in freely growing crown and grown on leached cinnamonic forest soil with gravity irrigation. Six years after planting the largest trunk cross-sectional area had the trees grafted on Weiroot 10. Trunk thickness was reduced significantly by the rest rootstocks, especially by Gisela 3. The trees on this rootstock had a smaller stem thickening – 1.4 to 5.9 times with ‘Van’ and 1.7 to 6.1 times with ‘Kozerska’, compared to the other rootstocks. Weiroot 10 induced the strongest crown growth and Gisela 3 – the smallest. Compared to Weiroot 10, the rootstocks Gisela 3, Gisela 5 and Gisela 6 reduced the tree crowns volume of ‘Van’ by 90.74, 84.03 and 31.76%, and of ‘Kozerskа’ by 87.27, 67.02 and 29.45%, respectively. The highest 3-year accumulated yield per tree of the both cultivars was achieved from trees on Weiroot 10 while the lowest yield was harvested on Gisela 3. In ‘Van’ higher yield efficiencies were calculated for Weiroot 10 and Gisela 5. About ‘Kozerska’ the highest yield efficiency (kg/cm2 of TCSA) was obtained for trees on Gisela 5 and the lowest - on Weiroot 10. No significant differences between the tested rootstocks were found in the mean fruit weight. The rootstocks produced no suckers in the tested cultivar-rootstock combinations. The highest mortality rate with ‘Van’ and ‘Kozerska’ was observed on Gisela 3 and Weiroot 10.