Jānis Lepsis, Līga Lepse, Darius Kviklys and Neeme Univer
In 2001, investigations were carried out on the Latvian origin cultivar ‘Suvenîrs’ grafted on seven pear rootstocks (MA, MC, BA29, Pyrodwarf, Brokmal, Kirchensaller Mostbirne and Kazrauðu bumbiere) in Polli (Estonia), Pûre (Latvia) and Babtai (Lithuania). The aim of the investigation was to evaluate pear rootstocks in different climatic conditions in the Baltic region. In Polli, all trees were planted in a dense planting, and therefore, trunk cross section area did not differ significantly between trees on different rootstocks. The most vigorous tree habit was observed in Lithuania for trees grafted on the rootstocks Kirchensaller Mostbirne and Brokmal, but in Latvia on Kirchensaller Mostbirne and Kazrauðu bumbiere. The highest dwarfing effect was observed for rootstock MC in both places. The highest cumulative yield from the orchard area was found for trees grafted on rootstocks of the quince group in all three locations of investigation. Nevertheless, the winter hardiness of the quince group rootstocks was not sufficient for Baltic climatic conditions. Good overwintering in Latvia and Lithuania was observed for trees on Pyrodwarf. Survival rate of trees grafted on Pyrodwarf in Estonia was unsatisfactory. The worse overwintering in Lithuania was observed for trees grafted on Brokmal. There was a dwarfing effect on trees and better yield on the vegetative propagated rootstocks included in the investigation, but none one of them can be recommended as perspective for commercial orchards in Baltic agro-climatic conditions.
Valda Laugale, Sandra Dane, Līga Lepse and Sarmīte Strautiņa
Strawberry (Fragaria x ananassa Duchense ex Rozier) is an important horticultural crop grown in Latvia. The aim of this research was to evaluate some newly introduced strawberry cultivars and perspective hybrids and to evaluate the efficiency of natural calcite leaf fertiliser (Megagreen®) on strawberry fruit quality and spread of pests and diseases. The trial was established in 2012 at Pûre, Tukums Municipality. Cultivars ‘Saint Pierre’, ‘Annapolis’, ’Sonata’, ‘Chambly’, ‘Elegance’, ‘Rumba’, ‘Honeoye’, ‘Senga Sengana’ and two hybrids: 35-1 and 39-1 were included in the investigation. Calcite fertiliser was applied four times per season in 2013 and 2014 by spraying on leaves in concentration 0.5%. Strawberries were grown on two row beds with black plastic mulch and drip irrigation. The evaluation was done for two seasons. Most of the evaluated newly introduced cultivars and hybrids had better fruit quality and resistance to diseases than control cultivars. Cultivars ‘Annapolis’, ’Rumba’, ‘Sonata’, ‘Elegance’, and 39-1 were selected as the most promising related to fruit quality and resistance. The application of calcite fertiliser (Megagreen®) on leaves had no statistically significant effect on strawberry fruit quality and resistance.
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.