Mekjell Meland

Research Professor

(+47) 906 28 538
mekjell.meland@nibio.no

Place
Ullensvang

Visiting address
NIBIO Ullensvang, NO-5781 Lofthus

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Abstract

The aim of this research was to analyze sugars and phenolics of pollen obtained from 15 different ‘Oblačinska’ sour cherry clones and to assess the chemical fingerprint of this cultivar. Carbohydrate analysis was done using high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD), while polyphenols were analyzed by ultra-high-performance liquid chromatography–diode array detector–tandem mass spectrometry (UHPLC-DAD MS/MS) system. Glucose was the most abundant sugar, followed by fructose and sucrose. Some samples had high level of stress sugars, especially trehalose. Rutin was predominantly polyphenol in a quantity up to 181.12 mg/kg (clone III/9), with chlorogenic acid (up to 59.93 mg/kg in clone III/9) and p-coumaric acid (up to 53.99 mg/kg in clone VIII/1) coming after. According to the principal component analysis (PCA), fructose, maltose, maltotriose, sorbitol, and trehalose were the most important sugars in separating pollen samples. PCA showed splitting off clones VIII/1, IV/8, III/9, and V/P according to the quantity of phenolics and dissimilar profiles. Large differences in chemical composition of studied ‘Oblačinska sour cherry’ clone pollen were shown, proving that it is not a cultivar, but population. Finally, due to the highest level of phenolics, clones IV/8, XV/3, and VIII/1 could be singled out as a promising one for producing functional food and/or in medicinal treatments.

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The objective of this study was to determine and compare the sugar profile, distribution in fruits and leaves and sink-source relationship in three strawberry (‘Favette’, ‘Alba’ and ‘Clery’) and three blueberry cultivars (‘Bluecrop’, ‘Duke’ and ‘Nui’) grown in organic (OP) and integrated production systems (IP). Sugar analysis was done using high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD). The results showed that monosaccharide glucose and fructose and disaccharide sucrose were the most important sugars in strawberry, while monosaccharide glucose, fructose, and galactose were the most important in blueberry. Source-sink relationship was different in strawberry compared to blueberry, having a much higher quantity of sugars in its fruits in relation to leaves. According to principal component analysis (PCA), galactose, arabinose, and melibiose were the most important sugars in separating the fruits of strawberries from blueberries, while panose, ribose, stachyose, galactose, maltose, rhamnose, and raffinose were the most important sugar component in leaves recognition. Galactitol, melibiose, and gentiobiose were the key sugars that split out strawberry fruits and leaves, while galactose, maltotriose, raffinose, fructose, and glucose divided blueberry fruits and leaves in two groups. PCA was difficult to distinguish between OP and IP, because the stress-specific responses of the studied plants were highly variable due to the different sensitivity levels and defense strategies of each cultivar, which directly affected the sugar distribution. Due to its high content of sugars, especially fructose, the strawberry cultivar ‘Clery’ and the blueberry cultivars ‘Bluecrop’ and ‘Nui’ could be singled out in this study as being the most suitable cultivars for OP.

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Abstract

The presence of pollinators in orchards is crucial to obtain high fruit set and yields of fruits. Despite the fact that sour cherry cultivars are mainly autogamous, insect visits are still of great importance for their propagation. In order to attract and reward pollinators, flowers have to provide adequate nourishment to them. Besides nectar, bees gather pollen, which are a prerequisite for normal colony growth and development of their broods. ‘Oblačinska’ sour cherry (Prunus cerasus L.), an autochthonous cultivar, is the most highly planted cultivar in Serbian commercial orchards. Since the cultivar is actually a mixture of different clones, variability in numerous traits and, particularly, its yields has been reported. Since phenolic compounds are considered to be fundamental pollen chemicals, the aim of this study was to determine the phenolic compounds profile in pollen collected from 15 ‘Oblačinska’ sour cherry clones with varying productivity levels. Solid phase extraction (SPE), combined with ultra-high-performance liquid chromatography coupled with a diode array detector and a triple quadruple mass spectrometer (UHPLC DAD-MS/MS), was used to analyse the polyphenolic profile of pollen. Among 23 components quantified, rutin was the most abundant phenolic compound. It ranged from 98.49 (clone V/P) to 358.83 mg kg-1 (clone III/9) and was observed to contribute, on average, 56% of the total phenolic compounds in pollen as quantified in different ‘Oblačinska’ sour cherry clones. In addition to this compound, clones contained significant amounts of chlorogenic acid (12.92%), astragalin (8.19%), and hyperoside (5.59%) as well. Cluster analysis grouped pollen clones in four different clusters, which showed that clones III/9, IV/8, and V/P had unique phenolic profiles. Despite the significant differences among the studied clones, the contents of chlorogenic acid, rutin, naringin, hyperoside, astralgin, and phlorizin were distinguishable between the clusters.

Abstract

Sweet cherry production worldwide is grown in the open land. Production technique is more or less similar with scions grafted on dwarfing and semi-dwarfing rootstock and trees arranged in single rows. Sweet cherries can be grown in Norway in areas with suitable local climatic conditions up to 60°N. All orchards have high density planting systems and are rain covered. Rain-induced fruit cracking in cherries remains a problem at an international level. The most common systems in Norway are multibay high tunnel systems and retractable rain covers. Covered orchard tunnel systems offer not only the advantage of rain exclusion but also allow additional manipulation of the environment, tree growth and fruiting. In general, sweet cherry high tunnel production gives increased yields of larger fruit than in the open land, but investment costs are higher. This overview article describes results from different experiments about high tunnels sweet cherry production mainly conducted at Nibio Ullensvang, Norway during the last ten years.

Abstract

Cherries (Prunus avium L. and Prunus cerasus L.) are economically important fruit species in the temperate region. Both are entomophilous fruit species, thus need pollinators to give high yields. Since cherry’s flower is easy-to-reach, bees and other pollinators can smoothly collect nectar as a reward for doing transfer of pollen to receptive stigma. Nectar in cherry is usually attractive for insects, especially to honey bee (Apis melifera) who is the most common pollinator. Nectar is predominantly an aqueous solution of sugars, proteins, and free amino acids among which sugars are the most dominant. Trace amounts of lipids, organic acids, iridoid glycosides, minerals, vitamins, alkaloids, plant hormones, non-protein amino, terpenoids, glucosinolates, and cardenolides can be found in nectar too. Cherry flower may secrete nectar for 2–4 days and, depending on the cultivar, produces up to 10 mg nectar with sugar concentration from 28% to 55%. Detailed chemical analysis of cherry nectar described in this chapter is focused on sugar and phenolic profile in sour cherry. The most abounded sugars in cherry nectar was fructose, glucose, and sucrose, while arabinose, rhamnose, maltose, isomaltose, trehalose, gentiobiose, turanose, panose, melezitose, maltotriose, isomaltotriose, as well as the sugar alcohols glycerol, erythritol, arabitol, galactitol, and mannitol are present as minor constituents. Regarding polyphenolics, rutin was the most abundant phenolic compound followed by naringenin and chrysin. Cherry cultivars showed different chemical composition of nectar which implies that its content is cultivar dependent.

Abstract

Sweet cherry production worldwide is grown in the open land. Production technique is more or less similar with scions grafted on dwarfing and semi-dwarfing rootstock and trees arranged in single rows. Sweet cherries can be grown in Norway in areas with suitable local climatic conditions up to 60°N. All orchards have high-density planting systems and are rain covered. Rain-induced fruit cracking in cherries remains a problem at an international level. The most common systems in Norway are multibay high tunnel systems and retractable rain covers. Covered orchard tunnel systems offer not only the advantage of rain exclusion but also allow additional manipulation of the environment, tree growth and fruiting. In general, sweet cherry high tunnel production gives increased yields of larger fruit than in the open land, but investment costs are higher. One more advanced way of producing sweet cherries is to grow the trees in small pots in greenhouses. A greenhouse gives opportunity to control the temperature regime and in that way program the maturity of the fruits. Research is conducted to test different cultivars, rootstocks, training methods in high-density production systems (1 tree m-2) with different fertigation levels. Preliminary results show that the yield potential is much higher than in the open land with larger fruits. Challenges are to optimize the water and nutrition supply and adjust the temperatures to obtain large yields of high quality fruits during different periods of the season.

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Abstract

European plums (Prunus domestica L.) blossom abundantly most years and often set too many flowers. If these excessive numbers of fruitlets remain on the trees until harvest, the crop would consist of small, unmarketable fruits of low fruit quality. Thinning agents like ammoniumthiosulphate (ATS), sulphur and soya oil desiccate flowers, especially stigma, which is the most sensitive tissue part of the flower. This way, the main effect of blossom thinning treatments is the disruption of pollination and fertilization. Thinning trials were conducted at a commercial orchard near the shore of the Hardangerfjord near Nibio Ullensvang, western Norway (60.2°N) on mature ‘Jubileum’ trees, all grafted on ‘St. Julien A’ rootstock. The trees were treated with 0.4, 0.8, 2 and 4% sulphur; a mixture of 0.4% sulphur + 2% soya oil and 1.5% ATS (liquid and powder formulations), at full bloom. All treatments were compared with hand-thinned and unthinned trees which were used as a control. Experimental trees were sprayed to the point of run-off with a hand sprayer during May 2008 and 2009 at full bloom. Flower thinners were efficient at relatively low temperatures which is a benefit in a cooler climate. In 2008 all thinning treatments reduced fruit set compared to unthinned controls for all cultivars. Sulphur and soya oil, both alone and in combination, were significantly less effective than ATS. In 2009, fruit set was higher and the effects of all thinning agents were lower. Fruit set decreased with increasing sulphur concentrations, but fruit thinning was not sufficient, even at the highest concentration. Both the liquid and powder formulations of ATS gave the same thinning effects. For all thinning treatments, both significant yield reductions and fruit weight increment were noticed during the experimental period. Fruit over color and soluble solids were generally higher and increased significantly with lower crop load, while fruit firmness (Durofel) and total acidity were less affected. In conclusion, different concentrations of sulphur had a moderate thinning effect and are not recommended for use as plum thinners under these conditions. Instead, 1.5% ATS application, (liquid and powder) applied at full bloom, resulted in adequate thinning of ’Jubileum’ plums under cool mesic northern climatic conditions.

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Abstract

Due to their Mendelian inheritance, microsatellites or SSRs (simple sequence repeats) can readily be used for parentage analyses of pear seedlings, thus revealing the female and male parents of the plant. However, in cases where obtained pear seeds display low viability, conducting a parentage analyses on the pear seeds themselves could be used in order to identify the male parent (successful pollinator). In this study, batches of seeds were extracted from fruits of the triploid ‘Ingeborg’ pear (‘Conference’ × ‘Bonne Louise’), the main commercial pear cultivar in Norway. Mature pears were collected from eight commercial pear orchards located in Ullensvang, at 60° North and seeds were collected. Genomic DNA was subsequently isolated from the obtained seed batches and genotyped using 12 microsatellite markers. The same markers were also used for the genetic characterization of ‘Ingeborg’ and five pear genotypes used as pollinators in the sampled orchards (‘Clara Frijs’, ‘Herzogine Elsa’, ‘Anna’, ‘Colorée de Juillet’ and ‘Belle lucrative’). The obtained SSR profiles were used in paternity analyses, as well as for gene assignment analyses. Both approaches identified pear ‘Clara Frijs’ to be the most successful pollinator in most of the sampled orchards. Subsequent S allele genotyping of ‘Ingeborg’ and five pear genotypes used as pollinators in the sampled orchards revealed that the preferential pollination by individual genotypes was not caused by gametophytic incompatibility or semi-compatibility.

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Abstract

The Norwegian newly bred pear cultivar, Celina/QTee®, which was launched in 2010, has been released from the Norwegian breeding program that was initiated in 1983. It was derived from the combination ‘Colorée de Juillet’ × ‘Williams’. In Norway the flowering is medium to late and it ripens in the beginning of September. It has large attractive fruits with a red blush. It has a good fruit quality, storability and shelf life. Cross pollination is necessary in order to have high yields of this diploid cultivar. Pollination of ‘Celina’ with pollen of four donors (‘Conference’, ‘Kristina’, ‘Anna’ and ‘Fritjof’), together with open- and self-pollination were studied in this experiment during the 2016 season in Norway. The dynamics of the pollen tube growth (third, sixth and ninth day after anthesis) in style (upper, middle and lower third) and parts of the ovary in all crossing combination, were observed by fluorescent microscopy. Besides giving the best results regarding the average number of pollen tubes in different parts of pistils and the dynamics of pollen tube growth, ‘Conference’ was the only one of which the pollen tubes didn’t show any incompatible signs while growing through the transmitting tissue of the ‘Celina’ style. According to those preliminary results, ‘Conference’ was the best pollenizer, followed by ‘Kristina’. The study has to be repeated for another season.

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Introduction and background: Autochthonous fruits in Bosnia and Herzegovina (B&H) represent great opportunities for fruit breeding, because they could be grown without costly agricultural inputs and offer valuable assets for the fruit processing industry providing a specific and different sensory taste for the fruit products. Hence, the objective of this study was to sensory evaluate fruits from 34 autochthonous apple and 29 pear cultivars in 2012 and 2013 from an ex-situ collection in B&H by eight trained panelists, using Quantitative Descriptive Analysis (QDA). Experimental: Flavour of fruits was described by the eight sensory attributes a) flavour: odour intensity, b) sweet, c) sour, d) green, fruit, e) floral flavour, f) typically, g) after taste and h) overall conception and subjected to principal component analysis (PCA) to visualise the sensory attributes. Results: For apple, the traditional cvs. ‘Prijedorska Zelenika’, ‘Paradija’, ‘Srebrenička’, ‘Bukovija’ and ‘Ljepocvijetka’ reached the best flavour scores in both years, while in pear, cvs. ‘Takiša’, ‘Hambarka’, ‘Dolokrahan’ and ‘Kačmorka’ exhibited the best flavour in both years, followed by cvs. ‘Begarika’, ‘Jeribasma’, ‘Ahmetova’ and ‘Hambarka’ with intense floral flavour and odour. In these tastings, B & H grown apple cv. ‘Golden Delicious’ also scored highly compared with cvs ‘Idared’, ‘Granny Smith’ and ‘Gala’ with a lesser characteristic apple flavour and pear cvs ‘Williams’ and ‘Sweet Harrow’ scored better than ‘Alexander Lukas’ and ‘Gellerts’ from B & H.

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Abstract

Tunnel production of sweet cherry results in higher yields of larger fruit than in the open. When cherry trees were grown under tunnels in Norway, fruit cracking was higher in a year when soils were saturated and when 20 ppm gibberellic acid was applied at straw color. In this study we evaluated the effect of soil moisture on fruit cracking under tunnels. In 2013, a trial on mature 'Sweetheart'/'Colt' trees growing under high tunnels was initiated. Each plot consisted of 8 trees, spaced 2×4 m apart with 'Lapins' as guard trees. Experimental design was a split-plot design with or without 20 ppm GA3 application at straw color; and three drip irrigation regimes (zero, deficit and full based on evapotranspiration). During the season, soil water content was monitored weekly. Due to unfavorable weather conditions during bloom time, crop loads were lower than normal. Average fruit sizes were large and GA3 application at yellow straw color resulted in small increases in average fruit diameter and fruit weight with all three irrigation treatments. Fruit cracking was very variable and occurred almost exclusively at the distal side of fruit and not on the stem side. GA3-treated fruit cracked slightly more than untreated fruit. There were no differences in fruit cracking due to irrigation scheme.

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Flowering is one of the most important factors in plant fertility. Fruit set in fruits is directly influenced by the beginning, sequence, flow, duration and abundance of flowering. The objective of this study was to evaluate the variability of flowering in 41 ‘Oblačinska’ sour cherry (Prunus cerasus L.) clones, and to recommend earlyflowering genotypes for growing in warmer locations where late spring frosts are rare, and some late-flowering clones for sites more susceptible for spring frost. Results from the three years period (2004-06), showed that ‘Oblačinska’ sour cherry clones flowered in a fixed sequence each year. Average for clone VII/2N, which flowered the earliest, was April 8 and petal fall took place by April 21, whereas clone III/1 bloomed last on April 14 and petal fall took place on April 25. Statistical analysis showed that almost all sub-phases of flowering were under the significant influence of both ecological and genetic factors. Besides, ecologic factors had the highest impact to the variability of beginning of flowering (79.8%), full bloom (76.8%), petal fall (80.2%) and duration of flowering (85.56%). Clones III/1, III/13, V/6 and V/2 were considered as late flowering, whereas clones VII/2N, VI/27, VI/28 and IX/P were early flowering, taking place five days earlier then previous group.

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In order to investigate the genetic structure and differentiation among north and south European apple germplasm, 141 apple accessions maintained in ex situ collections in Norway and 110 traditional and international apple accessions from Bosnia and Herzegovina (B&H) were analyzed using 8 microsatellite markers. Bayesian analyses, based on the microsatellite data, grouped most of the accessions into two major clusters. The first cluster consisted mainly of traditional and international B&H accessions, as well as Norwegian accessions derived mostly from foreign or formal breeding programs (‘James Grieve’, ‘Katja’, ‘Summerred’, ‘Bramleys Seedling’, ‘Elstar’, ‘Katinka’, ‘Belle de Boskoop’, ‘Jacques Lebel’, etc.). The second cluster consisted almost exclusively of traditional Norwegian accessions. Further analyses divided each cluster into two sub-clusters. Cluster 1.1 included Norwegian accessions derived from foreign or commercial breeding programs, international cultivars and B&H accessions introduced from Europe and North America during the rule of Austria-Hungarian Empire. Cluster 1.2 included traditional B&H accessions introduced during the reign of Ottoman Empire. Cluster 2.1 and 2.2 consisted mainly of traditional apple accession from Norway. The results obtained indicate a clear genetic structure and differentiation among north and south European apple germplasm, presumably due to climate adaptation and selection.

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Perennial fruit crops phenology such as cherry is an ideal bio-indicator of climate change due to their long-lasting features, in particular, dates of flower opening and full bloom. This implies i) the use of several generations of cherry trees/orchards and ii) the use of the same original cherry cultivars, which existed as bearing trees and were replanted after the orchard had been grubbed. A comparison of available definitions of phenological stages in cherry previously used independently throughout Europe showed overlaps and shortcomings; hence, harmonisation was reached in this respect in the COST Cherry FA 1104 working group 2 (cherry phenology and climate change) based largely on the acceptance of the BBCH scale. This contribution presents the agreed phenology stages in both visual and wording evidence. Similarly, this contribution presents the agreed cultivars to be monitored in future for phenology and climate change effects for harmonisation. For sweet cherry, this EU-wide harmonisation includes ‘Burlat’, ‘Cristobalina’ and ‘Rita’ as early, ‘Stella’ and ‘Van’ as medium flowering and ‘Sweetheart’, ‘Regina’ and ‘Bigarreau Noire de Meched/Germersdorfer’ for late flowering cultivars for climate change effects. For sour cherry, this harmonisation resulted in ‘Meteor korai’ and ‘Anglaise Hative’ for early flowering, ‘Chrisana Pandy’ and ‘Erdibotermo’ for medium flowering and ‘Schattemorelle’, ‘Iiva, Ujfehrtoifurtos (Balaton)’ for late flowering.

Abstract

Intensive sweet cherry production in tunnel covered orchard systems offer an advantage of reducing rain-induced fruit cracking. In May 2005 four Haygrove multibay tunnel systems were installed on a gentle slope at the experimental farm at Bioforsk Ullensvang, western Norway. In these tunnels, feathered 1-year-old sweet cherry ‘Sweetheart’/Colt trees were planted with two rows at a spacing of 2×4 m in each tunnel. Each tunnel was split into two halves and covered from the end of April to beginning of September with one of two different plastic covers, having different light spectral transmittance; Luminance THB film (absorbing infrared light) and traditional Visqueen clear UV polythene film. Climatic parameters were monitored inside and outside the tunnels from the beginning of May to the beginning of September each year and yield data and fruit quality parameters were recorded. In 2009, from May 7 to September 16 the average temperature measured outside the tunnels was 14.3°C. Temperatures exceed 25°C only on two days. Temperatures inside the tunnels were 0.3°C higher on average during the entire season but exceeded 30°C on the same two hot days. Temperatures under the Luminance film were slightly lower compared to the clear film and especially reduced the temperature build up on sunny days. The harvest period was the second half of August. Average yield tree-1 was 8.8 kg (11 t ha-1) in the fourth leaf and 18.8 kg (23.5 t ha-1) fifth leaf. There were no yield differences between the two different films. Fruit size measurements found that 80% of the fruits were larger than 30 mm in diameter in the fourth leaf and 51% in the fifth leaf. Total soluble solid content was generally high (17-18%) and no significant differences were found between the different films.

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Abstract

Phenological observations are considered to be sensitive tools for identifying plant responses to climatic changes. Over the last 10 years, the onset of the phenophases of sweet cherry (Prunus avium L.) during spring tended to be earlier than the previous two decades in Ullensvang, western Norway. The effects of air temperature during the winter and spring months were evaluated during two quinquennia (5-year periods), 1996-2000 (Q1) and 2003-2007 (Q2) selected due to similar mean winter and early summer temperatures, but markedly different spring temperatures. Average January-February temperatures were similar (3.3°C) in both of these two 5-year periods. However, average March and April temperatures were slightly warmer (4.0 vs. 3.2°C) and (7.3 vs. 6.9°C), respectively, in Q2 vs. Q1. These increases resulted in significantly earlier flower development. Average temperatures during the first half of May were similar for both quinquennia (10.2 vs. 10.1°C). The start of flowering (first bloom) of early maturing ‘Burlat’ and mid-season ‘Van’ were significantly different. Timing of flowering phenophases were statistically different between Q1 and Q2 for both cultivars. Mean data for ‘Burlat’ and ‘Van’ first bloom were 8 days earlier during Q2, May 2 for ‘Burlat’ and May 1 for ‘Van’. Full bloom occurred 3 days after first bloom and flowering ended 14 days after first bloom. First bloom during Q2 required 221 Baskerville-Emin Growing degree days (GDD) using a base temperature of 2°C. For the same time period in Q1, only 197 GDD were accumulated, which supports the observed temperature differences. Furthermore, we propose a flowering model for full bloom of both ‘Burlat’ and ‘Van’ in Ullensvang, which requires 254 Baskerville-Emin GDD using a base of 2°C starting on March 1.

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Abstract

Vitality of pollen, in vitro pollen germination and pollen tube growth (pollen tube length and pollen tube growth rate) were investigated in Oblačinska sour cherry in order to determine the differences between clones which have divergent yielding potential. For this purpose two ‘Oblačinska’ sour cherry clones with high fruit set and high yields (II/2, III/9) and two with low fruit set and low-yielding (XI/3 and XIII/1) were used in this study. Pollen germination was done on artificial medium containing 14% sucrose and 0.3% agar-agar at room temperature (23°C). Pollen tube growth was stopped with a drop of 40% formaldehyde, 1, 3, 6, 12 and 24 h after contact with the medium. The maximum percentage of germination ranged from 13.01% (clone II/2, after 1 h) to 54.19% (clone III/9, after 24 h). Pollen tube length varied from 64.84 μm (clone XIII/1, after 1 h) to >1,100 μm (clones II/2 and III/9, after 24 h). Pollen growth rate was quite high (up to 1.71 μm min-1) after 6 h of germination, but rather decreasing until 24 h of germination (0.560.83 μm min-1). The dynamics of in vitro pollen tubes growth among the clones were quite different, especially after 12 h and 24 h of germination. Clones that are singled out as fruitful (II/2 and III/9) gave much better results regarding pollen germination and pollen tube growth in comparison to clones which were characterized by low fruit set and yields (XI/3 and XIII/1).

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Professional and scientific networks built around the production of sweet cherry (Prunus avium L.) led to the collection of phenology data for a wide range of cultivars grown in experimental sites characterized by highly contrasted climatic conditions. We present a dataset of flowering and maturity dates, recorded each year for one tree when available, or the average of several trees for each cultivar, over a period of 37 years (1978–2015). Such a dataset is extremely valuable for characterizing the phenological response to climate change, and the plasticity of the different cultivars’ behaviour under different environmental conditions. In addition, this dataset will support the development of predictive models for sweet cherry phenology exploitable at the continental scale, and will help anticipate breeding strategies in order to maintain and improve sweet cherry production in Europe.

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The European plum cultivar 'Opal', widely grown in Scandinavia, frequently initiates too many flowers and set too many fruits. If excess fruitlets remain on the trees until harvest, the crop consists of small, unmarketable fruits of low fruit quality and return bloom will be reduced. The current study investigated effects of different crop loads established at blossom and fruitlet stages on yield, fruit quality and return bloom. For two seasons starting in 2008 on mature 'Opal'/'St. Julien A' trees, two crop loads 50 and 25% flowers reduced were established at full bloom and at 10-12 mm fruitlet size and compared with an un-thinned control treatment. Treatments were applied on single whole trees in a randomized complete block design with six replications. Spindle trees spaced at 3.0×5.0 m were selected for uniformity in growth habit, flowering intensity and trunk cross sectional area. Final fruit set varied from 63% on the control trees to 18% when thinned at bloom. Yield was negatively correlated with the fruit set response. Thinning at the fruitlet stage resulted in smaller fruits at the same crop level compared to flower thinning. Fruit quality parameters characterized by bright yellow skin background colour, red surface colour and the concentrations of soluble solids increased significantly as the crop load was reduced. Other fruit quality parameters like percentage acidity were not significantly different and did not show a clear response to the thinning. Return bloom was promoted most when trees were thinned at bloom the year before.

Abstract

European plum cultivar Jubileum (Prunus domestica L.) blooms abundantly most years and too many fruit can be set if flowers and/or fruitlets are not properly thinned. In 2007, 2008 and 2009, mature ‘Jubileum/St. Julien A’ trees were treated with ethephon either at full bloom, at concentrations of 250, 375 and 500 mg/l or when fruitlets averaged ~12 mm in diameter at concentrations of 125, 250 and 375 mg/l. In general, flower-thinning treatments reduced fruit set significantly. Fruit set decreased with increasing ethephon concentrations, and the highest rate of ethephon applied either at full bloom (500 mg/l) or post bloom (375 mg/l) resulted in excessive over-thinning. Up to 375 mg/l of ethephon was required at full bloom whereas only 125 mg/l of ethephon was required post bloom for marked fruitlet thinning. Yields confirmed the fruit set response and yield reductions were significant. In most years, all thinning treatments resulted in fruit larger than 38 mm in diameter compared to fruit from unthinned control trees. Fruit quality, characterized by blue surface color and soluble solids content was generally higher and increased significantly with the reduction in crop load. Fruit firmness of fruit from all ethephon applications was lower than that of the fruit from unthinned control trees. In contrast, titratable acidity did not show a clear response to ethephon thinning. Return bloom the following year was mostly unaffected by all ethephon applications compared to the control. In conclusion, an ethephon application at a rate of up to 375 mg/l applied at full bloom will result in adequate thinning of ‘Jubileum’ plums and achieved a target of about 10- 15 % reduction in fruit set. When weather conditions are not conducive during flowering, a post bloom ethephon application at 125 mg/l may be applied however, this should only be considered in years of excessive flowering and as a last resort.

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Abstract

When establishing an apple orchard it is important to stimulate the growth of young trees to fill up their allotted space in the row and minimize the time to come into full production with high quality fruit. In May 2012 two-year-old 'Summerred'/'M.9' knip trees were planted at the experimental farm at NIBIO Ullensvang, western Norway. The planting distance was 4×1 m (2500 trees ha-1). Three fertigation schemes were established (zero; low - 0.15 g N m-1 row day-1, and high nitrogen - 0.30 g N m-1 row day-1) and two crop loads allowed (low and high). In the year after planting the crop loads were limited to zero and five apples tree-1, respectively. In the third leaf the crop loads were adjusted by hand to 15 apples and 30 apples tree-1, respectively. The experimental design was a randomized blocks with four replications and 10 trees treatment-1. No significant effects of N-fertigation on soil NO3-, NH4+ or N-min contents were found. However, N-fertigation increased the leaf nitrogen content the whole season and leaf N were ≥ than the standard adequacy range (1.5-2.0%). Trees reached the desirable height of 3 m in the third leaf. Trunk circumference and number of branches per tree increased from second to third leaf, but were not significantly influenced by the N-fertigation. In the third leaf the high crop load trees yielded 7 kg tree-1 (17.5 t ha-1) and the low crop load 4 kg tree-1. Fruit weights were negatively correlated with the crop loads. Small differences in fruit quality attributes were found. Return bloom was not affected after the second leaf. However, the high crop load in the third leaf clearly reduced the amounts of return bloom in 2015, irrespective of the amount of N-fertigation.

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Prohexadione-Ca, an acylcylohexadione, is a plant growth retardant jointly developed by BASF, Germany and Kumiai Chemical Industry, Japan. In 2012, a trial on 11-year-old 'Aroma'/'M 9' apple trees growing on the experimental farm at NIBIO Ullensvang, western Norway was initiated. Trees were treated with prohexadione-Ca (trade name Regalis®, 10% prohexadione-Ca as active ingredient) 10 days after full bloom (June 6) at concentrations of 125 or 250 g ha-1; other trees were also sprayed 10 days after full bloom and again one month later (July 5) at the same concentrations and compared against an untreated control. Treatments were applied to individual whole trees in a randomized complete block design with four replications. Prohexadione-Ca treatments significantly reduced shoot growth of treated apple trees. Two treatments with 125 g or one treatment of 250 g reduced growth by ~80%. Prohexadione-Ca had little effect on yield and fruit quality. Shoot growth was also retarded in the year following application and this is attributed to a carry over effect of the prohexadione-Ca application(s).

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Abstract

Triploid apple cultivars are often favored by human selection due to their increased fruit size, even though they possess higher requirements in terms of pollination compared to their diploid counterparts. However, similar to the sensory characteristics, preferences for the size and shape of apple fruit are not universal, but culturally dependent. In order to investigate the influence of selection pressure on the frequency of triploid genotypes among different traditional apple germplasms, 141 apple accessions maintained in ex situ collections in Norway and 115 traditional and international apple accessions from Bosnia and Herzegovina (B&H) were analyzed using 8 microsatellite markers. Genotypes possessing more than two alleles per locus were deemed to be triploid. The results of SSR analyses from this and comparable studies indicate that the triploid apple cultivars are much more frequent among the traditional apple germplasm from Southern Europe than they are among the traditional apple germplasm from Northern Europe. The possible causes for these results are also discussed.

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Abstract

Apple genetic resources in Norway are currently conserved within a number of local clonal archives. However, during establishment of these ex situ collections, primary focus was not on capturing as much of the diversity as possible, but instead on preserving cultivars of particular importance to specific fruit-growing areas. To identify redun- dancies within the collection as well as to assess the genetic diversity and structure of apple germplasm currently being conserved in Norway, eight microsatellites were used in genetic characterization of 181 apple accessions. Overall, 14 cases of synonym or possibly mislabeled accessions were identified, as well as several homonyms and duplicates within and among the analyzed collections. The information obtained should contribute to overall better management of the preserved germplasm. Bayesian analysis of genetic structure revealed two major clusters, one containing most of the foreign cultivars, while the other consisted mainly of traditional Scandinavian cultivars, but also some very winter-hardy genotypes such as ‘Charlamovsky’, ‘Gravenstein’, ‘Transparente Blanche’, and ‘Wealthy’. Analyses of molecular variance (AMOVA) detected a signifi- cant genetic differentiation among the clusters ( fCT = 0.077; P < 0.01). The results of the Bayesian analyses do not indicate a strong differentiation between the foreign and the Norwegian apple accessions, however, they do suggest that climate adaptation has had a significant influence on the genetic structure of the preserved germplasm. Overall, apple accessions currently maintained ex situ in Norway represent a diverse germplasm which could be very valuable in future breeding programs, especially for the Scandinavian climate.

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Abstract

The response of three-year-old 'Summerred' trees to crop load regulation by the chemical thinning agent Brevis® was tested in comparison with different levels of hand thinning. Brevis® was applied once or twice at a dosage of 1.1 and 2.2 kg ha-1 when fruitlets were approximately 15 and 19 mm in diameter at the time of the first and second application, respectively. All Brevis® applications significantly reduced the number of fruits tree-1. Both the single application of 2.2 kg ha-1 and the two-fold application of 1.1 kg ha-1 thinned the tree to the target crop load level of 30 apples tree-1. The degree of thinning by the single application of 1.1 kg ha-1 Brevis® did not significantly increase fruit weight and resulted in a very strong inhibition of return bloom similar to that observed in the untreated controls and trees hand thinned to 60 fruits tree-1. Return bloom was positively related to the level of thinning obtained. At the target fruit load of about 30 apples tree-1, return bloom was around 40% of the bloom in the year of the thinning trial. A further thinning to circa 15 fruits tree-1 increased return bloom to approximately 60%. In conclusion, 'Summerred' trees planted as two-year-old feathered trees should not bear more than 20 to 25 fruits tree-1 in their 3rd leaf in a northern climate to avoid the onset of biennial bearing and to ensure regular annual yields. Only then sufficient numbers of flower buds will develop to have the chance to obtain a good crop in the next year.

Abstract

Crop load adjustments in European plum trees (Prunus domestica L.) require thinning either by hand (mechanical) or chemical means to achieve marketable size, fruit quality and to overcome alternate bearing. Efficient tools for crop load management are highly desirable, since only a few chemical thinners are registered and hand thinning is labor intensive and costly. Gibberellic acid (GA3) was tested as a novel approach to regulate the crop load of the plum cultivar ‛Opal’ at Ullensvang, western Norway. The objective was to reduce flower bud induction in the “off-year” thus adjusting crop load the subsequent year. In 2008, an “off-year”, GA3 was applied to 9 year-old ‘Opal’ trees as a high volume spray to the point of run-off at 50 ppm or 100 ppm at either 5 weeks after full bloom or 10 weeks after full bloom, or on both dates and compared with untreated control trees. Trees were unthinned the first year but then thinned to commercial standard the following year. In the year of application, total yield was recorded and fruit quality evaluated. Return bloom, fruit set, yield and fruit quality were assessed the subsequent year. In general, there were no significant differences in crop load of all treated trees compared to untreated trees in the year of application (non-target crop) however, fruit weight increased slightly on those trees when GA3 was applied 5 weeks after full bloom compared to all other treatments and untreated trees. The following year (target crop) fruit set was significantly reduced for all GA3 treatments. The most effective application time was 5 weeks after full bloom. Before thinning, initial fruit set was greatest on untreated trees as well as on those trees treated with GA3 10 weeks after full bloom. Fruit weight and fruit colour were significantly better on trees with the least fruit set. GA3 applications had no effect on fruit firmness. It is concluded that GA3 is an effective tool for inhibiting flower bud induction in an “off-year” thus enabling crop load management the subsequent “on-year”.

Abstract

‘Summerred" apples (Malus domestica) Borkh are highly susceptible to biennial bearing if not properly thinned. This results in erratic yields and also affects fruit quality adversely. Between 2003 and 2005 ‘Summered"/‘M9" trees were treated with ethephon at concentrations of 250, 375 and 500 mL·L-1 when most king flowers opened (ca. 20% bloom) or at concentrations of 500, 625 and 750 mL·L-1 when the average fruitlet size was 10 mm in diameter. The experimental design was a completely randomised block design with 6 whole tree plots per replication. Trees were sprayed to the point of run-off with a hand applicator only when temperatures exceeded 15ºC. Within two weeks after the second application fruit set was reduced linearly with increasing concentrations of ethephon to less than 1 fruitlet per cluster at the highest concentrations used. Most thinning treatments reduced fruit set significantly compared to unthinned trees. Fruit numbers per tree decreased significantly with increasing ethephon concentrations, and the highest concentrations of ethephon applied during bloom or when the average fruitlet size was 10 mm in diameter resulted in over-thinning. Yield results confirmed the fruit set response where yield reductions were significant at highest concentrations of ethephon (2.1 kg·tree-1) compared to hand-thinned trees (7.3 kg·tree-1) in 2005. All thinning treatments resulted in higher percentage of fruits larger than 60 mm diameter average fruit size compared to unthinned control fruit. Thinning resulted in significantly higher soluble solid contents, and this was especially so for hand-thinned trees. Other fruit quality parameters like yellow/green background color did not show a clear response to thinning. Fruit firmness, however, decreased slightly in all ethephon treated trees whereas return bloom was improved on all thinned trees. It is recommended that ethephon be applied at a rate of 375 mL·L-1 when king flowers open or at a rate of 625 mL·L-1 when the average fruitlet size is 10 mm in diameter. These treatments thin ‘Summerred" apples to a target of about 5 fruits·cm-2 per trunk cross sectional area or 50-70 fruits·100 flower clusters-1 without impacting fruit quality, yield or return bloom the following year.

Abstract

In vitro dose responses of several calcium and potassium salts were determined on some commercially significant plant pathogens including: Helminthosporium solani, Fusarium oxysporum f. sp. pisi race 2, Colletotricum coccodes, Phytophthora cactorum, Phytophthora cinnamomi, Phytophthora erythroseptica, Phytophthora infestans, Phytophthora megasperma, Pythium ultimum and Venturia inaequalis. Mycelial growth inhibition was both salt-specific and dose-related. Pythium ultimum was completely inhibited by ≥75 mg·L-1 calcium propionate, but needed ≥ 300 mg·L-1 of calcium acetate and ≥ 40 mL·L -1 of potassium silicate for complete inhibition. Phytophthora infestans was completely inhibited by ≥150 mg·L-1 calcium acetate, ≥150 mg·L-1 calcium propionate or ≥ 5 mL·L-1 potassium silicate. Phytophthora cactorum was completely inhibited by ≥ 300 mg·L-1 calcium propionate, but required ≥ 600 mg·L-1 calcium acetate and ≥10 mL·L-1 potassium silicate for complete inhibition. Phytophthora cinnamomi was completely inhibited by calcium propionate at ≥ 600 mg·L-1, or by ≥10 mL·L-1 potassium silicate. Only potassium silicate inhibited Phytophthora megasperma, Phytophthora erthroseptica, V. inequalis and H. solani at concentrations of ≥ 5mL·L-1, ≥ 20 mL·L-1, ≥ 40 mL·L-1 or ≥ 80mL·L-1 respectively. Potassium acetate did not completely inhibit any of the pathogens in this study when tested at concentrations ≤ 1200 mg·L-1.

Abstract

This paper describes briefly the phenomena of alternate bearing of European plums and point out that more detailed investigations about physiological factors, in particular plant hormones, involved in the flowering process are of great importance.

Abstract

Fruit samples of seven sweet cherry cultivars grouped into three different groups of fruit flesh firmness (soft-fruited: 'Ranna Ljaskovska', 'Vista' and 'Sunburst', medium firm: 'Ulster' and 'Sylvia' and firm cultivars: 'Van' and 'Lapins') were harvested over a three week period with 3-4 d intervals prior to, during and after normal harvest time in 1997 and 1998 in Ullensvang, western Norway. Fruit firmness was measured at each harvest date along with measurements of soluble solids content (SSC), air temperature, precipitation and estimation of fruit colour. Corresponding samples picked at normal harvest date were stored in normal air atmosphere at temperatures 2 degrees C and 8 degrees C, respectively, and firmness was measured during storage with 3-5 d intervals. All the tested cultivars reached normal firmness, colour and SSC at harvest both years. Fruit were generally darker in 1998 than in 1997. All cultivars showed a more or less distinct reduction in firmness over the period prior to and slightly after normal harvest. Exceptions were 'Sunburst' in the 1998-season, that increased in firmness after normal harvest date, and the two firmest cultivars that increased in firmness over the ripening period in 1997. Generally, firmness increased during the first part of storage followed by a decrease after 1-2 weeks, the decrease being usually earlier and more distinct at 8 degrees C than at 2 degrees C. 'Van' in 1998 showed no change in firmness development throughout the storage period but a small increase in the last part. 'Lapins' in 1997 had however, a pronounced drop in firmness in the middle of the storage period followed by an increase. All the tested cultivars were more firm at normal harvest time in 1998 than in 1997, except the two firm-fleshed cultivars 'Van' and 'Lapins'. The warm and sunny 1997-summer produced softer fruits than the cold and rainy 1998-season, except for the firm-fleshed cultivars. It was anticipated that the many contradictory results of sweet cherry fruit firmness reported by other authors may be caused by differences in weather conditions as demonstrated.

Abstract

‘Elstar" is the latest-maturing commercial apple cultivar grown in Norway, with high fruit quality when properly managed. In May 2006, an experiment with four different crop loads [2, 4 ,6, or 8 flowers or fruitlets cm-2 trunk crosssectional area (TCSA), respectively] was established at two different stages [first bloom (FB), or 20-mm diameter fruitlets] and compared to unthinned control trees. Fruit growth was measured on individual fruit for each treatment throughout the season at weekly intervals. Thinning at FB gave a significantly lower final percentage fruit set than thinning to the same cropping level at the 20-mm fruitlet stage. However, fruit weights and soluble solids contents (SSC) were significantly higher, and the background fruit colour improved when trees were thinned at FB. The final number of fruit at harvest was less than the amount established at FB, or at the 20-mm fruitlet stage. There were significant differences between treatments in final fruit numbers per TCSA, which reflected the different crop loads. Fruit weights and SSC values were highest with the lowest crop load, and decreased with increasing crop loads.There was also a strong crop-load effect on the extent of return bloom per tree in the subsequent year. Trees thinned at FB had significantly more flower clusters than those thinned at the 20-mm fruitlet stage of. Untreated control trees had the lowest number of flower clusters. The amount of return bloom declined with increasing crop load. Second year crop loads and fruit weights were highest when trees were thinned at FB to two or four apples cm-2 TCSA in the previous year. Trees with the highest crop load had the lowest crop load in the following year. Fruit quality was generally high for all treatments.

Abstract

Due to a late harvesting season compared to that found in other European countries, the sweet cherry industry in Norway is now expanding, aiming for export markets. Cultivars producing high quality fruit that ripen late (late July and throughout August) and that are suitable to grow in high density production systems are sought. In addition, early ripening cultivars are sought for local marketing in early and middle July. Testing cultivars and advanced selections has been carried out at Ullensvang Research Centre since 1959. During the last decade, 130 cultivars and advanced selections have been included in the testing program. Important parameters like fruit size, fruit firmness, low fruit cracking, high and precocious yield, fresh appearance and good flavour have been evaluated. Based on the results from this testing program, the following cultivars are currently recommended: a) for early season: `Burlat", `Moreau" and `Merchant", b) for mid-season: `Giorgia", `Chelan", `Samba", `Techlovan" and `Van", c) for late season: `Lapins", `Kordia", `Regina" and `Sweetheart".

Abstract

Some high density sweet cherry orchards in Norway suffer from decay of trees resulting in death or reduced vigour of trees. A survey monitoring healthy and infected trees from several orchards found differences between cultivars and rootstocks in sensitivity of tree decay. In order to investigate this cherry tree decay further, new field trials were established in 2002 with trees of the cultivar Van grafted on the two rootstocks Prunus avium seedling and Colt and trained as central leader trees. Two parallel trials were planted; one in the soil of an old cherry orchard and the other in the soil from agricultural land where no fruit production had been conducted in advance. During the first years significant larger annual vegetative growth measured as trunk girth, annual shoot growth and leaf areas were registered from the trees growing in the virgin soil. In the replanted cherry soil, trees grafted on the rootstock Colt grew more vigorously than the seedling rootstock based on leaf areas and shoot growth measurements. The rootstock Colt may be the answer for avoiding cherry replant diseases.

Abstract

Histological properties of the graft union between a rootstock and scion may provide a mechanistic explanation why dwarfing rootstocks are able to reduce the growth of the tree. In order to investigate the relationship between growth and the amount of functional xylem tissue of potted sweet cherry trees, an experiment was conducted during 2002-2003. One year old field budded and bench grafted (from greenhouse) sweet cherry trees of the cultivars Van, Ulster and Lapins in all combinations of the three rootstocks Prunus avium seedling, Colt and Gisela 5 were grown in pots for two growing seasons. After shoot extension had terminated when trees were in full leaf the second year, the total growth of the different parts of the trees and the functional area using safranin staining were measured. The total mass production (tree dry weight, the length of two year old wood and number of leaves) was significantly larger in the budded trees. Similarly the trunk cross sectional area was significantly larger 10 cm above and in the middle of the graft union, but not 10 cm below it. The Colt trees were the most vigorous followed by the seedling and Gisela 5. Minor differences between the different cultivars were registered. Xylem staining with aqueous safranin combined with quantitative image analysis showed that the rootstock stem had a higher proportion of stained tissue than the scion stem. Sections taken in the middle of the graft tissue and 10 cm above showed that the proportion of stained tissue declined proportionally with the distance from the roots. The total area of stained stem xylem was larger for the two vigorous rootstocks compared to Gisela 5. Small differences were observed between cultivars and propagation methods.

Abstract

The performance of the plum rootstocks Marianna, Pixy and Wangenheim using St. Julien A as a standard to the cultivars `Avalon", `Edda", `Excalibur", `Jubileum", `Reeves" and `Victoria" was assessed in a field trial in western Norway at 60" North. Trees were planted in spring 1999, the plant material was one-year-old whips, spaced 2.0 x 4.5 m and formed with a central leader as free spindles. Soil management was grass in the alleyways and herbicide strips 1-m wide along the tree rows. Tree vigour, yield, fruit size and yield efficentcy were evaluated for the six subsequent years. Tree size was significantly affected by the rootstocks after six years growth. Wangenheim produced the smallest and St. Julien A and Pixy the largest trees as measured by trunk cross-sectional area in average for the different cultivars. St. Julien A and Pixy were the most productive rootstocks for the cultivars. However, Pixy produced significant larger yields per tree to the cultivar `Reeves" than St. Julien A. Trees on Pixy were the most yield efficient for all cultivars with the exception of `Victoria". The fruit sizes were in general large for all cultivars and became little affected by the different rootstocks. Fruit quality characterized by the content of soluble solids was in general high and did not differ between trees on the various rootstocks. The cultivar `Avalon" had the highest contents of soluble solids.

Abstract

During the period 1998-2000, thinning trials were conducted using bloom thinners on mature European plum trees at Ullensvang and at fruit growers sites in western Norway. In 1998, unsprayed control and handthinned `Victoria" trees were compared with trees treated at full bloom with a single application of 1% Armothin® or 1.5% ammoniumthiosulphate (ATS). The same program was conducted in the following two years with the addition of a single full bloom treatment with 250 ppm ethephon and a post-bloom application one month after full bloom with the mixture 10 ppm 1-napththaleneacetic acid (NAA) and 75 ppm ethephon. High volume sprays were conducted the first two years and low volume the last year. Thinning trials testing 1-1.5 % ATS and 5-7 % lime sulphur in comparison with unthinned and handthinned trees to the cultivars `Opal" and `Victoria" were conducted in 2000, at growers sites. Generally, thinning treatments reduced crop load and enhanced fruit quality (fruit size, soluble solid content, fruit firmness and ground and surface colour), but the results varied from year to year. Fruit set was reduced to about half of control values and the percentage of class 1 fruits was doubled compared to the control trees. High volume sprays to running off was more effective than low volume. The cultivar `Opal" was more sensitive to ATS than `Victoria" and a low dosage recommended. All thinning compounds caused some minor leaf injury but no fruit damage. The flower thinners were efficient at rather low temperture. No differences in the amount of gummosis (internal disorder of the fruits) were observed due to treatments on the `Victoria" plums. Return bloom was improved by thinning. In conclusion, a single dilute application at full bloom of 1% Armothin®, 1.5% ATS or 250 ppm ethephon or one application of the mixture 10 ppm NAA-75 ppm ethephon four weeks after bloom reduced fruit set and crop load and increased the fruit quality and return bloom to the cultivar `Victoria". Similar results gave one dilute spray with 1 % ATS or 5 % lime sulphur at full bloom to the cultivar `Opal".

Abstract

Betre lystilhøve i frukttrea aukar veksten hjå tre og frukter, og fruktkvalitetsfaktorar som farge og oppløyst turrstoff vert betre. Sjølv om daglengda under norske veksttilhøve er lang, er den samla lystilgangen mindre enn på sørlegare breiddegrader pga den korte vekstsesongen. Metodar som aukar ljostilgangen, t.d. lysreflekterande duk under trea, vil vera gunstig for norsk fruktdyrking. Ein har prøvd ein voven plast duk (Extenday (R)) i frukthagar på Vestlandet. Der radavstanden var 4 m, har ein strekt ut 3m brei duk på bakken langs køyregangane og festa med gummiband til trea på kvar side. Der radavstanden var 5 m, nytta ein 4m brei duk. Duken låg ute frå midten av juni til etter hausting. Det var ingen temepratureffekt av duken. Men det var 5 gonger så mykje lys i trekruna hjå tre som sto i felt med reflekterande duk i høve til kontroll tre. I køyregangen var det 3 gonger så mykje lys over duk som i køyregangar med gras. I Aroma var eple frå tre frå felt med duk større, søtare og med meir raud dekkfarge enn frå kontroll trea. Det var særleg stor skilnad frå eple på dei nedte greinene. Med omsyn til fastleik og syreinnhald var det ikkje sikre skilnader. Men Streif-indeks viste at refleksduken framskunda mogninga.

Abstract

I eit felt med "Excalibur" og "Prinlew" plommer vart køyregangen dekka med kvit reflekterande duk for å betra ljostilhøva i trekruna. Duken låg i hagen frå 2 veker etter bløming til etter at plommene var hausta i midten av september. Der det ikkje var nytta reflekterande duk var fruktene nede på treet grønare, hadde mindre dekkfarge og lågare innhald av oppløyst turrstoff enn fruktene oppe i trekrunene. Fruktene frå tre som hadde stått over reflekterande duk var like godt farga og hadde same syrinnhald og fastleik om dei var hausta oppe eller nede på trea. Men det var også for desse trea høgare innhald av oppløyst turrstoff i fruktene oppe i trea i høve til dei som hadde vakse nedst i trea. Reflekterande duk gav jamnare mogning hjå plommene oppe og nede i trea. Dermed kan ein klara seg med færre haustingar. Temperaturen var ikkje heva der ein nytta duk, og duken svekka grasveksten i køyregangane.

Abstract

Combinations of covering and fungicide applications were tested on two sweet cherry cultivars; Van during two years (2001 and 2002) and Lapins three years (2001"2003). The following treatments were tested in 2001 and 2002: (i) covering during flowering and from 5 to 6 weeks prior to harvest and throughout harvest, no fungicides applied, (ii) as (i) but fungicides were applied once or twice between the two covering periods, (iii) covered 5 to 6 weeks prior to harvest and throughout harvest, fungicides applied two or three times prior to covering, and (iv) uncovered throughout the season, fungicides applied two or three times in the period from flowering towards harvest. In 2003, the trees were covered only from 5 to 6 weeks prior to harvest and throughout harvest. Both treatments that year received fungicide applications during flowering, but one of the treatments was left unsprayed during the green fruit period prior to covering. Every combination of covering and fungicide applications reduced total fruit decay at harvest significantly compared to a full fungicide programme and no covering. In three of four trials when the trees were covered during flowering and prior to harvest, and fungicide applications were omitted in the green fruit phase between the covering periods, no significant increase in fruit rot occurred compared to treatments where fungicides were applied. However, in one trial there was a significant increase in fruit rot by leaving out one fungicide spray during that intermittent period. Furthermore, if fungicides were only applied during flowering and not on green fruit before covering in 2003, a significant increase in fruit rot occurred. Thus, leaving out fungicide applications during that supposedly less susceptible green fruit period, increased the risk of acquiring fruit rot. Applying fungicides during the green fruit stage significantly reduced the amount of brown rot in four of five trials and anthracnose in one of five trials. No negative effect on fruit quality was found from the extended covering periods. It can be concluded that covering effectively replaced fungicide applications during flowering and prior to harvest.

Abstract

The performances of the plum rootstocks Plumina® Ferlenain, Ishtara® Ferciana, Jaspi® Fereley and the pentaploid open pollinated seedling of Mariana P 8-13 compared with St. Julien A as a standard, for the cultivars "Opal" and "Reine Claude GF 1119" were assessed in a field trial in western Norway at 60" North. This trial was one part of an international plum rootstock trial located in seven European countries and organized from INRA Bordeaux. Trees were planted in spring 1994; spaced 2.0 x 4.0 m and formed with a central leader as free spindles. Soil management was grass in the alleyways and herbicide strips 1-m wide along the tree rows. Tree vigour, yield, fruit size and yield efficiency were evaluated for the seven subsequent years. Tree size was significantly affected by the rootstocks. P 8-13 produced the largest trees for both cultivars as measured by trunk cross-sectional area. The smallest trees were produced on Plumina® Ferlenain for the cultivar `Opal" and on Jaspi® Fereley for `Reine Claude". The cultivar `Opal" was the most productive and gave three times larger crop than "Reine Claude" on average for the six cropping years. The "Reine Claude" trees came two years later into production than "Opal". There were small differences between the different rootstocks in productivity: However, the rootstock Plumina® Ferlenain produced significant lower crop than the other rootstock for `Opal". Trees on Jaspi® Fereley were the most yield efficient for `Opal" and Plumina® Ferlenain for `Reine Claude". The fruit sizes were in general medium to small for both cultivars and became little affected by the different rootstocks. The average fruit size was about 29 g for `Opal" and 22 g for `Reine Claude". Fruit quality characterized by the content of soluble solids was high for `Reine Claude" with average 20 % and 15 % for `Opal" and did not differ much between trees on the various rootstocks.

Abstract

Resultat frå forsøk med ulike dekkesystem for søtkirsebær sin effekt på mikroklima og fruktkvalitet er skildra i ein vitskapleg artikkel på engelsk. Resultata er delvis publisert på norsk i følgjande artikkel: Børve, J., A. Stensvand & M. Meland, 1997. Verknad av plastdekking på rotning hjå søtkirsebær. Informasjonsmøte i plantevern 1997 Grønn forskning 2/97. 252-255.

Abstract

Årleg turrstoffproduksjon vart estimert frå åtte år gamle epletre med sortane "Fuji", "Royal Gala" og "Braeburn" poda på grunnstamma M9 og forma som slank spindel. Både frisk- og turrstoffproduksjon auka liniært med mengda av ljos som vart oppfanga i trea. Denne samanhengen tilsvarar ei avling på 16.9 tonn pr. daa med ei ljosoppfanging på 90 %. Energien som vart omdanna frå ljos i vekstsesongen til turrstoff i New Zealand var tilsvarande som i England. Skilnaden mellom desse to landa er at New Zealand har ein lengre vekstsesong og høgare innstråling. Turrstoffproduksjonen var fordelt til frukt, treaktig vev og blad med ei fordeling til frukt på 74, 72 og 63% for dei tre sortane "Braeburn", "Fuji" og "Royal Gala".

Abstract

An intensive field planting of `Edda", "Opal" and "Mallard" plum trees (Prunus domestica L.) all grafted on the semidwarf rootstock St. Julien A was established in 1993 at Ullensvang Research Centre, western Norway at 60 ° North. The objectives were to evaluate four different single row planting systems (vertical axis, free spindle, hedgerow and Y-trellis) and three planting densities ( 0.5, 1.0, 1.5 x 4 m for the Y-trellis and hedge trees and 2.0 x 4 m for the central leader trees) in a northern climate. These planting distances give a range of tree density of 1250 - 5000 trees per ha. The experiment gave a small yield in the third leaf on all canopy systems. During the first four cropping years, the yields/ha were positively correlated with tree density. Cumulative yield per hectare was highest on the Y-trellis and hedge trees with the highest density (5000 trees per ha). In the fourth leaf, the Y-trellis trees gave 15 tons per hectare. No differences in fruit size or the soluble solids content among canopies or densities were found.

Abstract

The cherry cultivars "Van", "Ulster" and "Burlat" grafted on the rootstocks seedling, `Colt" and `Gisela 5" were evaluated for important fruit quality parameters at Ullensvang Research Centre during the 1998 season. The largest fruit size was found on the cultivar/rootstock combinations `Van"/seedling, `Ulster/Colt" and `Burlat/Gisela 5". Other parameters like fruit firmness, stone weight, soluble solids, titratable acids and pH of the fruit juice were registered as well.