Results from the 11-Year Evaluation of 10 Rootstocks of the Sweet Cherry Cultivar 'Stella'

In the years 1997-2007, the influence of the rootstocks Gisela 5, Gisela 4, Gisela 12, Weiroot 10, Weiroot 13, Weiroot 53, Weiroot 72, Weiroot 158, the elite of the series Giessen, Gi-497/8, and also of P1 (seedling of P. mahaleb L.) on the growth and fruiting of the trees of the 'Stella' cultivar, was studied. The trees were planted in December 1996 in the experimental field of the Agricultural University in Plovdiv at distances of 6.0 x 4.5 m. They were grown under conditions of irregular gravity irrigation. By the end of the 11th vegetation, the most vigorous growth was induced by P1, Weiroot 10 and Weiroot 13, the differences between them being insignificant. The trees on the remaining rootstocks (compared to the crown volume on P1) had growth vigour as follows: Weiroot 158 - 47%, Gi-497/8 - 46%, Weiroot 53 - 40%, Weiroot 72 - 38%, Gisela 4 - 37%, Gisela 12 - 33% and Gisela 5 - 10%. Based on the fact that the mean annual shoot length of the trees on Gisela 5 during the last 5-6 vegetations was proven to be the weakest (about and even below 10 cm), we could determine Gisela 5 as a typically dwarfing one, and Gisela 4, Gisela 12, Gi-497/8, Weiroot 53, Weiroot 72 and Weiroot 158 as dwarfing to semi-dwarfing. The highest suckering ability was demonstrated by Gisela 4, Weiroot 10 and Weiroot 13, and the weakest by Weiroot 53, Weiroot 72 and Weiroot 158. The rootstocks P1, Gisela 5, Gisela 12 and Gi-497/8 did not form suckers. In total for the years 1999-2007, the rootstocks induced approximately the same yield (kg/cm(2)) with the exception of Gi-497/8, which diferred to them. Certain rootstocks, however, behaved differently in specific periods. For example, Gisela 5 induced the highest yield in the years 19992001, and the lowest one during the last 3 vegetations. The smallest size of the fruit was induced by Gisela 4 and Gisela 5. Out of the 6 trees planted in every variant, the greatest number of perished ones were those on Gisela 5-50%, followed by Gi-497/8, Weiroot 53 and Weiroot 72-33%. The indicated unsatisfactory results concerning Gisela 5 indicated that the potential of these plants has almost been depleted at the end of the 11th vegetation. The exhaustion of the trees was also observed on other dwarfing rootstocks (Gisela 4, Weiroot 53 and Weiroot 72), but only by initial indications. Gisela and Weiroot 158 were distinguished by the best complex results.