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The results presented in this paper relate to the time and duration of flowering of highbush blueberry as well as fruit set in the conditions of flower isolation and free visitation by pollinating insects. Observations were carried out in the years 2001- 2004 at a plantation located in Niemce near the city of Lublin. Six cultivars: ‘Bluecrop’, ‘Bluejay’, ‘Croatan’, ‘Darrow’, ‘Northland’ and ‘Spartan’, were covered by the study. The flowering period of the studied highbush blueberry cultivars was in May in three years of study, whereas in 2004 in May and June. Depending on the year, it lasted from 14 up to 21 days, on the average. Significant differences were found in the life span of a single flower which, depending on the cultivar and conditions prevailing during flowering, bloomed from 5 up to 10 days (the average for all the years for all the cultivars). With free access of pollinating insects, highbush blueberry set an average of 92 false-berries per 100 flowers, whereas only 40 during spontaneous self-pollination under the isolating cover. In each year of study, irrespective of atmospheric conditions prevailing during flowering as well as the time and duration of flowering, fruit set of the investigated cultivars in flowers freely accessible to pollinating insects should be considered to be good or very good.
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The aim of the work was to examine the health status of 11 highbush blueberry (Vaccinium corymbosum L.) cultivars cropped on the plantations in a south-eastern region of Poland as well as to determine the composition of fungus species colonizing their stems. The performed observations of health status indicated that stems with disease symptoms were found on almost all bushes. Three types of symptoms were found: spots on stems, from which mainly Topospora myrtilli was isolated, widespread stem necrosis inhabited by Phomopsis archeri and necrosis of stem tops caused by Botrytis cinerea. Moreover, the following isolates of fungi were obtained Cytospora, Phoma, Fusarium, Alternaria and Seimatosporium vaccinii, Myxothyrium leptideum and Sordaria fimicola. It was confirmed that the most malignant pathogen of highbush blueberry in the studied region was Topospora myrtilli.
Blueberries are tasteful fruits and are widely believed to be the source of health beneficial compounds, especially phenolics. Freezing is one of the methods of prolonging their supply beyond vegetative season. The aim of the study was to estimate fruit chemical composition of four blueberry cultivars (‘Spartan’, ‘Bluecrop’, ‘Jersey’ and ‘Blueray’). Dry weight, total sugar, total acidity, vitamin C and total polyphenol content were determined in fresh berries and after 6 and 12 months of freeze-storage at –25℃ . In generally, ‘Bluecrop’ berries showed the most stabile chemical composition (dry weight, total sugar, total acid content) whereas ‘Spartan’ ones the least. Considering the all storage period the least pronounced changes occurred in total acid content (increase by 0.1 g citric acid · 100g⁻¹) while the most substantial in vitamin C content, decrease by 57% (‘Bluecrop’) – 72% (‘Jersey’).
The objective of the study carried out during 2004-2007 was to evaluate the in­fluence of three types of substrates (peat, sawdust and cocoa husk) on yield, quality and chemical composition of highbushblueberries cv. 'Sierra'. On 4-year average, the lowest yield per a bush (0.89 kg) was obtained from bushes grown in cocoa husk substrate and these berries had the lowest weight of 100 fruit (64 g) and were the smallest. On the other hand, they had the highest firmness, measured both vertically (512 G mm-1) and horizontally (275 G mm-1). The highest soluble solids content (14.45%) and titratable acidity (1.02 g of citric acid equivalents 100 g-1 ) were found in fruit harvested from bushes growing in peat. The substrates did not affect significantly total sugar (11.98-12.30 g 100 g-1) and vitamin C contents (26.0-27.9 mg 100 g-1). The nitrates content in blueberries was low, ranging from 17.5 (peat) to 34.7 mg kg-1 (sawdust) whereas the content of nitrites varied from 0.85 (peat) to 1.10 mg kg-1 (sawdust). Blueberries obtained from peat- and cocoa husk- bedded bushes had significantly higher total phenolics content (231.03 mg and 222.29 mg per 100 g-1, respectively) compared to these grown in sawdust (181.74 mg 100 g-1). Similarly, the berries originating from peat- and cocoa husk- grown plants showed higher total anthocyanin content (144.55 mg 100 g-1 and 146.73 mg 100 g-1, respectively) than fruit collected from sawdust-bedded bushes (120.92 mg 100 g-1). Taking into account the yield alone, the best effects were obtained from 'Sierra' bushes grown in sawdust. However, regarding chemical composition, the berries from bushes grown in peat and cocoa husk were richest in nutritional components and, especially, in phenolic compounds.
The experiments were carried out on highbush blueberry 'Herbert' both on in vi­tro cultures and plants in vivo. In the case of the in vitro study, the modified Zim­merman and Broome (1980) medium was used. For the first subculture dikegulac was tested at a 0.1-10 mgl-1 concentration together with 2iP (5mgl-1). For the second subculture, dikegulac (1-4mgl-1) was added both into medium supplemented with 2iP (10 mgl-1), and into medium without 2iP. In the case of the in vivo study, dikegu­lac (100-1000 mg l-1) was applied as a foliar spray on four-month old plantlets. Dikegulac (0.1-5 mg l-1) gradually slowed down the elongation of axillary shoots in vitro, in the presence of 2iP at a lower (5 mg l-1) concentration. It also retarded devel­opment of adventitious shoots, while proliferation of axillary shoots was unaffected. Cultures grew very slowly when 2iP was omitted regardless of the concentration of the retardant Plants sprayed with dikegulac (1000 mg l-1) solution in vivo developed more lateral shoots which were shorter, and the plants had reduced leaf blades. Cut­tings collected from plants treated with retardant rooted better, compared with the control. Dikegulac may be useful to keep the germplasm bank and in propagation of highbush blueberry, both in vitro and through cuttings.
The increased cultivation of highbush blueberry in Poland has been paralleled with enhanced damage to this crop by different pests and diseases, including soft scales. We have carried out trials to assess methods for controlling soft scales of the genus Parthenolecanium in highbush blueberry grown in open fields or under a plastic tunnel, with an approach based on integrated pest management (IPM) principles. The reduction of Lecanium scale population using alternative products, with mechanical mechanisms of action, was similar to that achieved with treatments of different formulations of neonicotinyl-based pesticides; sometimes they were even more effective on protected crops. Control programs on plantations with a large population of Lecanium scales based on the application of these alternative products in spring and at harvest time and chemical compounds in autumn resulted in a very high efficacy and are considered the most suitable strategies to assure yields without residues and a reduced impact on the environment.
The influence of melatonin (MEL) in comparison with IAA, IBA (all at 5.71 µ M), and auxin-free (0) medium on development of highbush blueberry (Vaccinium corymbosum hort. non L.) ‘Herbert’ in vitro shoot cultures was examined. Depending on the kind of hormone in vitro cultures consisted of various number of axillary (AX) and adventitious (AD) shoots. The influence of melatonin on in vitro cultures was intermediate but more similar to IAA than IBA. Production of axillary shoots on media supplemented with MEL and IAA was comparable and higher than on medium with IBA. In contrast to IAA melatonin reduced development of adventitious shoots. Contrary to IBA-obtained cultures AX shoots grown on ‘IAA’, ‘0’, and ‘MEL’ media resembled AD shoots.
Viral diseases are a worldwide problem of blueberry which a major limiting factor for production. A survey for Blueberry scorch virus (BlScV) by DAS-ELISA in various organs of highbush blueberry conducted from May 2010 to April 2011, showed the occurrence of these virus in cvs Bluecrop and Herbert, which showing virus-like symptoms. Samples of plant materials (bud flower, flower, leaf, bark) were collected individually from each highbush blueberry plant of every cultivar. It was established that the detection of virus of each the investigated bushes cvs Bluecrop and Herbert depended on the tested plant materials as well as the period in which the tests were performed. The effectiveness of the virus detection varied for the investigated cultivars. The presence of the BlScV was confirmed in leaves samples with specific primer pair which amplifies a 430 bp fragment of the 5’-proximal ORF I [RNA-dependent RNA polymerase (RdRp)].
The aim of the study was to examine response of ‘Jersey’ highbush blueberry to boron (B) fertilization. The experiment was carried out in 2002-2003 at a private plantation in Central Poland on mature blueberries planted on a sandy loam soil with pH 4.1, low organic matter status, and medium available B content. Blueberries were supplied with B by foliar applications or broadcasting. Foliar B sprays were done in the spring or the fall. Spring B sprays were performed at the beginning of blooming, at petal fall, and 3 and 6 weeks after the ending of flowering. In each spring spray treatment, B was used at a rate of 0.2 kg ha⁻¹. Fall B spray was done 5 weeks after fruit harvest using 0.8 kg B ha⁻¹. Soil B was applied at the stage of bud break at a rate of 2 kg ha⁻¹. Blueberries unfertilized with B served as control. The results showed that soil B application and spring B sprays increased B status in flowers and leaves. However, B fertilization, regardless of application mode, had no effect on plant vigor, the number of flowers per cane, fruit set, mean fruit weight, berry firmness, and yielding. Berries of blueberries sprayed with B in the spring had increased soluble solids concentrations. It is concluded that: (i) B fertilizer requirements of ‘Jersey’ highbush blueberry are low, and (ii) at hot water extractable B concentration in a soil below 0.37 mg kg⁻¹ and/or at B status in leaves of current season shoots below 37 mg kg⁻¹, spring B sprays should be applied in blueberry culture to increase soluble solids concentration in fruit.
The aim of this work was to investigate the effect of freezing and long-term frozen storage on total phenolic, total anthocyanin contents and antioxidant activity of highbush blueberries (Vaccinium corymbosum L.). In addition, a HPLC method was developed for the determination of individual anthocyanins and chlorogenic acid contents. Blueberries were frozen at –18°C and –35°C and were stored at these temperature conditions for six months. Derivatives of malvidin and delphinidin accounted for 61% and 22% of total anthocyanin contents in fruit, respectively. Measurements of the antioxidant activity and bioactive compounds contents of blueberries showed there were no significant differences between fresh and frozen fruits. Also, at the end of frozen storage period, antioxidant activity remained significantly unchanged compared with the values measured just after the freezing process
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