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Fruit set is a crucial stage in the process of yield formation, which is influenced by environmental factors, growing technologies and peculiarities of genotype. The aim of the study was to evaluate the quality of pollen (viability and germination capacity) and the effect of weather before and during flowering on fruit set in sour cherry cultivars ‘Latvijas Zemais’, ‘Zentenes’, ‘Bulatnikovskaya’, and ‘Orlica’. The research was carried out in Institute of Horticulture (Latvia University of Agriculture) in 2009-2016. Good pollen viability and germination was found for cultivars ‘Latvijas Zemais’ and ‘Bulatnikovskaya’. Negative effects of increasing air temperature (in the range of 7.7 to 17.5 °C) and relative humidity (in the range of 51.4 to 88.5%) was observed for all cultivars during flowering. The effects of diurnal temperature fluctuations, wind and the amount of days with precipitation differed depending on sour cherry cultivar.

The climate in Latvia is marginal for grape growing. Nevertheless grapes have a comparatively long cultivation history as well as diverse current developments. The 15th century can be considered as a starting point of grape growing in Latvia, while in the 17th century larger plantations were established in the western part of the country. Wine was made and some even exported. Later there were several more or less successful attempts of grape cultivar introduction, breeding and growing. Therefore diverse and locally adapted grape germplasm is available. The total area occupied by grapes in Latvia is not large (about 20 ha), but plantations are increasing and becoming noteworthy production places and tourism attractions. Several groups of grape growers should be noted: gardening enthusiasts, collectors and owners of commercial plantations (1 to 5 and more ha). The Latvian breeders have achieved good results in developing outdoor grapes for such marginal growing conditions, by using genotypes of Vitis vinifera, V. labrusca and/or V. amurensis. The main selection criteria are very early ripening, winter-hardiness, resistance to mildew (Plasmopara viticola and Erysiphe necator), good taste and appropriate sugar content in berries. Comprehensive screening of available grape germplasm and its evaluation was performed to characterize grapes grown in Latvia, identifying more than 200 genotypes in 18 collections. Available large diversity of cultivars and hybrids, which represents plant material of several Vitis species as well as interspecific crosses, may be used as valuable parent material for breeding in northern countries.

Tocochromanols profile in kernels recovered from fruit pits of seven sweet cherry (Prunus avium L., family: Rosaceae) cultivars was studied. Four tocopherol homologues (α-T, β-T, γ-T, and δ-T) were quantified in all tested samples by RP-HPLC/FLD method. The RP-UPLC-ESI/MSn analyses allowed to detect trace amounts of two tocotrienol homologues (α and γ). The concentration of individual tocopherol homologues in kernels of different sweet cherry cultivars, expressed in mg/100 g dwb, was in the follow range: 3.03–4.96 (α-T), 0.01–0.11 (β-T), 32.26–37.51 (γ-T), and 0.95–1.69 (δ-T). The γ-T was the main tocopherol homologue identified in sweet cherry kernels and constituted approximately 88 % of total detected tocochromanols. The percentage composition of the individual tocopherol homologues in kernels of different sweet cherry cultivars was comparable.

Izmēģinājums iekārtots Latvijas Valsts Augļkopības institūtā 1998. gada stādījumā ar šķirnēm ‘Iputj’ un ‘Krupnoplodnaja’. 2008. gadā uzstādot VOEN seguma sistēmu, veikta ievērojama vainaga pazemināšana un atjaunošana gan variantā ar segumu, gan arī kontrolē. Dati par saldo ķiršu augšanu, ražošanu un augļu kvalitāti variantos ar segumu un bez tā iegūti no 2009. gada līdz 2012. gadam. Segums katru pavasari, sākot ar 2009. gadu, uzklāts pirms ziedēšanas un noņemts pēc ražas novākšanas. Šķirnei ‘Krupnoplodnaja’ pēc apgriešanas zem seguma bija vērojama izteikta tendence ātrāk atjaunot vainaga tilpumu, lai gan matemātiski to pierādīt neizdevās. Seguma ietekme uz ražas lielumu nebija pierādāma, lai gan tendence bija pozitīva. Variantā zem VOEN seguma iegūti vairāk realizācijai derīgu augļu. 2012. gadā, kad ķiršu ienākšanās laikā bija sevišķi daudz nokrišņu, zem seguma 85% augļu bija derīgi realizācijai, bet bez seguma tikai 53%. Segums ievērojami samazināja puves bojāto augļu daudzumu, bet putnu bojāto augļu daudzums bija atšķirīgs pa gadiem. Pirmos divus gadus to bija vairāk zem seguma, bet 2011.-2012. gada variantā bez seguma. Šajos gados ar augstu ticamību pierādījās seguma pozitīva ietekme uz augļu vidējo svaru, zem seguma tie bija lielāki. Seguma pozitīva ietekme uz šķīstošās sausnas un fenola saturu augļos bija pierādāma tikai

A trial was established at the Latvia State Institute of Fruit-Growing to evaluate the effectiveness of woodchip mulch and drip irrigation on sour cherry growth, yield and fruit quality as compared to untreated control trees. Sour cherries are rich in biologically active compounds. Therefore the aim of this investigation was to examine the biochemical content of sour cherry fruits as influenced by growing conditions and cultivar. Fruit of the cultivars 'Bulatnikovskaya', 'Desertnaya Morozovoi', 'Latvijas Zemais', 'Orlica', 'Shokoladnica', 'Tamaris' and 'Zentenes' were analyzed for several biochemical characteristics: including soluble solids, total acids, phenolic compounds and anthocyanins. There were significant differences in fruit biochemical composition depending on cultivar and growing method. Fruit of the cultivars 'Shokoladnica' and 'Desertnaya Morozovoi' had significantly higher soluble solids content than the other cultivars. Both cultivars had a tendency to increased soluble solids content in the control treatment. The significantly highest concentrations of the anthocyanins and phenols in the fruits were recorded for the cultivar 'Tamaris'. High contents of phenols and anthocyanins were detected also in fresh fruit of the cultivars 'Shokoladnica' and 'Bulatnikovskaya'.

Twenty-five different new sweet cherry rootstocks have been tested at Dobele HPBES. The first (I) trial of 4 rootstocks (Gisela 4, Gisela 5, Weiroot 154 and F12/1) with two cultivars ('Iputj' and 'Krupnoplodnaya') was planted in 1998. The second trial (II) was established in 1999 as part of the International sweet cherry rootstock trial with 23 different rootstocks. The cultivar used was 'Lapins'. In trial I, Gisela 4 and Gisela 5 seemed to be the most promising rootstocks, as regards yield efficiency. Weiroot 154 only showed better yield efficiency than F12/1. When fertigation was used, tree size and trunk diameter were considerably larger on F12/1 than in the other rootstocks. The results of the first yields per trunk cross sectional area in trial II showed the best effect in the third year after planting when using dwarfing rootstocks PHL-B, PHL-A, Gisela 107/1, as well as Edabriz. The largest increase in trunk diameter was found in rootstocks: Weiroot 10, Gisela 4, Weirooot 158, Gisela 523/02 and Hexaploid Colt. Gisela 4, Gisela 5, Gisela 148/8 and PHL-B induced trees to crop early in their lives following planting.