EVALUATION OF VIGOROUS AND DWARF PLUM ROOTSTOCKS IN THE HIGH DENSITY ORCHARD IN CENTRAL POLAND

Abstract

The influence of two seedling rootstocks originated from Prunus cerasifera var. divaricata Borkh. and 'Wangenheim Prune' (P. domestica L.) as well as four clonal rootstocks (GF 655/2, 'Jaspi', 'Ishtara', St. Julien A) on the tree growth, yield and fruit weight of 'Hanita' and 'Dabrowice Prune' plum cultivars was investigated in 2000-2007. Results obtained showed that these rootstocks modified the growth intensity of trees of both investigated plum cultivars. The trees grafted on 'Ishtara' rootstock were the most vigorous in this experiment. The least growth was on trees grafted on 'Wangenheim Prune' seedlings. Trees grafted on 'Ishtara' rootstock had a significantly higher cumulative yield per tree than those on other evaluated rootstocks. It was also proved that rootstocks had an influence on the fruit weight of both cultivars. Generally, the fruits harvested from trees grafted on Wangenheim Prune seedlings had the smallest weight. The fruit weight of trees on 'Ishtara' rootstock was the largest. Health status examination of trees of both cultivars showed that some trees grafted on 'Jaspi' rootstocks were not winter hardy enough in Polish weather conditions. As a result of this many trees grafted on this rootstock were firstly attacked by fungal diseases (Leucostoma cinta Hohn., Valsa malicola Urban.) and then they died. Taking into consideration features such as the quantity and quality of fruit crop, results from the experiment with high density planting of trees showed that plum rootstocks GF 655/2, 'Ishtara' and ST. Julien A performed well in Polish climatic conditions. In contrast, plum trees grafted on 'Wangenheim Prune', a dwarfing rootstock, require fertile soil, no specific replanting problems and appropriate high mineral fertilization.