Preliminary performance of six plum rootstocks on six European plum cultivars in Latvia

The seedlings of myrobalan (Prunus cerasifera) are the most popular rootstocks for plums in Latvia and give large trees. However, dwarfing rootstocks are essential for establishing high density orchards which give earlier yields and lower production costs. An experiment at the Institute of Horticulture, Latvia University of Agriculture was planted in spring 2015 The performance of the dwarfing plum rootstocks Wangenheim prune, VVA-1, S766, M633 and Weiwa was compared against the industry standard Prunus cerasifera. Onto these rootstocks, scion cultivars ‘Victoria’, ‘Jubileum’ and the Latvian new cultivars ‘Ance’, ‘Adelyn’, ‘Sonora’ and ‘Lotte’ were grafted and assessed in a trial with six replicates. In the trial one-year-old trees were planted, the spacing of trees on P. cerasifera was 5×2.5 m while on dwarfing rootstocks it was 5×1.5 m, with two trees plot^‑1. After the first growing years there were no significant differences between trunk cross section areas, among different combinations of cultivars and rootstocks. A high number of suckers was found for all cultivars on the rootstocks P. cerasifera (1.3), M633 (1.6), S766 (1.1) evaluating in scores from 1 to 5. Only few suckers were found for all cultivars on the rootstocks Weiwa (0.3 points) and VVA-1 (0.2 points). Almost no suckers were found for all cultivars on rootstock Wangenheim (0.07 points). The highest amount of perished trees (20.8% trees in average for all cultivars) was found on the rootstock P. cerasifera while the lowest number of perished trees was on the rootstock S766 and Wangenheim prune (16.7%). Rootstocks Weiva and M633 did not show any tree loss. The cultivar ‘Victoria’ on rootstock S766 and cultivar ‘Ance’ on Wangenheim prune showed the earliest yield.