Tree growth and some other characteristics of new columnar apple cultivars bred in Holovousy, Czech Republic

Several characteristics related to tree growth, their fruitage and resistance against scab and powdery mildew were assessed during 2007-2008 on five new cultivars in comparison with the ancestral McIntosh Wijcik, in which 4 out of 5 had their pedigree. In several plots established between 1998 and 2006, the trees, which were on different rootstocks predominantly planted in spacing 4 × 0.5 m, were grown as vertical cordons practically without any pruning or shaping. Besides the first years after the planting these columnar trees generated very limited side branching. The cultivars mutually differ in tree vigour, spurring density, and size of fruiting spurs. Mean annual prolongation of central axes in the case of the trees on vigorous rootstocks varied within 30.8-57.5 cm, however, on M 9 rootstock it was distinctly shorter (23.4-34.1 cm). Beyond cultivar and rootstock the length of the annual prolongation was also significantly influenced by fruit set level. Trees of the Kordona cultivar were generally the most vigorous while those of Pidi were the weakest. The biennial pattern of bearing observed to an extent on nearly all the cultivars was connected with tendency to over-crop the trees. The highest annual yield equal to 10.3 kg was generated on trees of Kordona on MM 106, which corresponds to a total harvest of 25.7 t/ha. Cultivars Herald and Slendera possessed combined resistance both to scab and powdery mildew, whereas Kordona and Cumulus were resistant only to scab, but were in different degrees susceptible to mildew.