Dzintra Dēķena, Alena V. Poukh, Kersti Kahu, Valda Laugale and Inga Alsiņa
Proper selection of rootstock that is adapted to local growing conditions and climate is one of the most important preconditions for obtaining high yield in intensive plum orchards. The aim of the investigation was to evaluate the influence of different rootstocks on the productivity of two plum cultivars: ‘Kubanskaya Kometa’ (Prunus rossica. Erem.) and ‘Victoria’ (P. domestica L.) in different climatic conditions. The following sixteen rootstocks known in Europe were used in the trial: eight vegetatively propagated (‘St. Julien A’, ‘Brompton’, ‘Ackermann’, ‘Pixy’, ‘GF 8/1’, ‘G 5/22’, ‘GF 655/2’, ‘Hamyra’) and eight generatively propagated (‘St. Julien INRA2’, ‘St. Julien d’Orleans’, ‘St. Julien Noir’, ‘Brompton’, ‘Wangenheims Zwetsche’, ‘St. Julien Wädenswil’, ‘Myrobalan’, P. cerasifera var. divaricata). The evaluation was made in experimental orchards in Latvia, Estonia and Belarus. Orchards were established in spring 2001. Trees were planted at spacing 3 × 5 m in four replications, three trees per plot. The data obtained in years 2008-2015 are presented. The yield was influenced by rootstock and differed between years, growing regions and cultivars. The meteorological conditions during wintering period had significant influence on yield for trees on all evaluated rootstocks.
Dzintra Dēķena, Ina Alsiņa, Valda Laugale and Kersti Kahu
The selection of appropriate rootstock is the main precondition for obtaining a high yielding and sustainable plum orchard. In the Northern climate, plum overwintering is especially important, where winter hardiness of flower buds is one of indicators. This investigation was carried out during three wintering periods (2010–2013) at the Institute of Horticulture in Pūre (Latvia) and the Polli Horticultural Research Centre (Estonia), in orchards planted in 2001. The aim of the investigation was to evaluate the influence of different rootstocks on the viability of flower buds during winter for two plum cultivars in two growing regions. European plum ‘Victoria’ and hybrid plum ‘Kubanskaya Kometa’ grafted on eight clonal and eight seedling rootstocks were used in the investigation. Bud samples were taken two times during winter: end of January and end of March. The viability of flower buds and flowering intensity were determined in the laboratory. The viability was determined as dehydrogenase activity using triphenyl tetrazole chloride (0.5%), where in living cells the colourless substance due to enzymatic activity turns into a brightly coloured product — formasan. The optical density of colour was determined with a spectrophotometer at 485 nm. Both cultivars ‘Kubanskaya Kometa’ and ‘Victoria’ had higher flower bud viability in Polli compare to Pūre. In both growing regions, the highest activity of dehydrogenases for cultivar ‘Kubanskaya Kometa’ was on rootstocks ‘Myrobalan’, ‘St. Julien INRA 2’, ‘Wangenheims Zwetsche’ and for cultivar ‘Victoria’ — on rootstocks ‘Ackermann’, ‘Brompton’ seedlings, and ‘St. Julien d’ Orleans’. The dehydrogenase activity of in flower buds had a tendency to decrease during winter.
Dzintra Dēķena, Jānis Lepsis, Ina Alsiņa, Līga Lepse and Kersti Kahu
The issue of the influence of rootstock on winter-hardiness of plum (Prunus × rossica Erem.) tree flower buds in the Baltic region is becoming important. The choice of rootstock is the main precondition for obtaining a high yielding and sustainable plum orchard. Freezing of flower buds is one of the most significant damages in winter for stone fruits. The aim of the investigation was to determine the relationship between concentration of dry matter and reducing sugars in annual shoots during winter and wintering ability of trees. The dynamics of reducing sugar concentration in one-year-old shoots during winter was investigated during two successive seasons in two locations. Orchards were planted in 2001 in Latvia and in Estonia. The well-known plum cultivar ‘Kubanskaya Kometa’ (Prunus rossica Erem.) was grafted on eight clonal rootstocks (‘St. Julien A’, ‘Brompton’, ‘Ackermann’, ‘Pixy’, GF8/1, G5/22, GF655/2, and ‘Hamyra’) and eight generative propagated rootstocks (‘St. Julien INRA 2’, ‘St. Julien d’Orleans’, ‘St. Julien Noir’, ‘Brompton’, ‘Wangenheims Zwetsche’, ‘St. Julien Wädenswill’, ‘Myrobalan’ and Prunus cerasifera var. divaricate). Shoot samples were harvested two times during winter — at the end of January and at the end of March. Dry matter concentration (mg·g−1) and the concentration of reducing sugars (mg·g−1 DM) by Fehling’s solution method was determined. Tree flowering intensity was scored using a scale from 1 to 5, where 1 = no flowers and 5 = abundant flowering. Dry matter concentration in plum shoots varied among rootstocks, years and growing location. In Pūre, Latvia, the largest differences in dry matter concentration were found for trees grafted on ‘St. Julien INRA2’ (in 2011–2012) and ‘Brompton’ cuttings (in 2012–2013) but in Polli, Estonia for trees grafted on G5/22 (in 2011–2012) and ‘Myrobalan’ (in 2012–2013). One of the most stable rootstock/graft combinations in the trial when GF655/2 was used as rootstock, where dry matter concentration was between 491 and 525 mg·g−1, and reducing sugars between 37.5–49.2 mg·g−1, and flowering intensity between 2.5 and 4.
Ave Kikas, Kersti Kahu, Liina Arus, Hedi Kaldmäe, Reelika Rätsep and Asta-Virve Libek
The aim of the investigation was to evaluate the effect of genotype and growing conditions on blackcurrant fruit weight and biochemical composition. The trial was carried out during the years 2011 and 2012 in South Estonia with two cultivation methods (conventional and organic) and eight genotypes of different genetic background, including two Scottish, ‘Ben Alder’ and ‘Ben Lomond’; two Swedish ‘Intercontinental’ and ‘Titania’; a Belarusian ‘Pamyati Vavilova’, and three recently selected genotypes from the Estonian blackcurrant breeding programme, ‘Karri’, ‘Asker’, and ‘Mairi’. From each genotype and in both cultivation sites 500 g of fruit at full maturity was collected in three replications. Fruit weight, soluble solids (SS), sugars, organic acids, sugar/acid ratio, and ascorbic acid (AsA) concentrations were determined. Fruits from the organic cultivation site were smaller and contained more SS and sugars, they also had a higher sugar/acid ratio than conventionally grown berries. Organic acids and AsA concentrations were higher in berries from conventional cultivation systems compared to the organic ones. ’Karri’ had the highest SS and sugar concentrations and sugar/acid ratio and the lowest concentration of acids on average over the years and cultivation methods. The highest AsA concentration was determined in ‘Asker’ and ‘Ben Lomond’.