The yield and fruit quality of two plum cultivars on different rootstocks

Myrobalan (Prunus cerasifera) seedlings are the most popular rootstocks for plums in Latvia. Only recently wider investigations were begun about the vegetatively propagated rootstock suitability to conditions of Latvia, their influence on plum cultivar productivity and fruit quality. In 1996–1999 several trials were planted, where different plum cultivars were grafted on several vegetatively propagated rootstocks – vigorous AP-1 and Myruni, dwarf St. Julien A, GF 655/2 and semi-dwarf Druzhba and SVG 11-19, as well as two forms of Prunus cerasifera seedlings. The trials included several cultivars. Two of them – diploid ‘Kometa’ and hexaploid ‘Victoria’ are the most grown cultivars in Latvia and the subject of this study. In the period of full yield the data of four years were analyzed to evaluate the influence of rootstocks on yield and fruit weight of both mentioned cultivars. On the selected seedling form PU-20651 of Prunus cerasifera and on Myruni the diploid cultivar ‘Kometa’ was more productive than on the other rootstocks, which was statistically significant also. The smallest yield per tree of this cultivar was obtained on the rootstocks GF 655/2 and St. Julien A. The average fruit weight depended on the yield value. The hexaploid cultivar ‘Victoria’ yielded significantly better on rootstock AP–1 than on Druzhba and PU-20651 seedlings. Influence of yield or rootstock forms on the average fruit weight was not found.