Abstract
Long-term field trials with the apple cultivar ‘Krista’ on different vegetative rootstocks were held at the Polli Horticultural Research Centre (58°07`N, 25°32`E) in Southern Estonia in 2005-2015. Trees were grafted on 13 rootstocks: M26, M27, P59, E75, B9, B396, B491, MTT1, Supporter 1, Supporter 2, Supporter 3, Supporter 4, and MM106. The apple cultivar ‘Krista’ is well suited for growing in the climatic and soil conditions of Estonia. The cultivar performs best on vegetative rootstocks that are well-adapted to the Estonian climate: MM106, E75, B396, M26, M27, and P59. The rootstocks Supporter 1, Supporter 2, Supporter 3, and Supporter 4 did not turn out to be suited for growing in Estonia. The trees grafted on rootstocks MM106, E75, MTT1, and M26 grew taller, had a bigger crown spread and crown volume. In dense orchards with the planting scheme 4 × 1.5 m, trees with a smaller crown diameter may be grown on rootstocks MM27, P59, and Supporter 4. During the trial, the largest yields were harvested from trees grafted onto rootstocks MM106, MTT1, B396, M26, E75, and B9. Some rootstock combinations appeared to be positively related to average fruit weight in some years, but the same cannot be concluded for the whole duration of the trial.