Blueberry Cultivars Research Articles

The seasonal progression of the reproductive phenology of two southern highbush blueberry (V. corymbosum L. interspecific hybrids) cultivars in the Western Cape, South Africa

• The reproductive phenology of SHB cultivars ‘8-42’ and ‘9-02’ was documented for the first time in such depth and per whole plant. • The timing and peaks of the phenological stages quantified on individual plant basis were similar between the two locations - for both cultivars. • The duration of the phenological stages was influenced by micro climate. • The intensity of bud development was accurately illustrated per cultivar and location. • The differences in the intensity of phenological development on bud and plant level will serve as baseline for further studies on carbohydrate allocation to explain the differences in yield. The objective of this study was to evaluate the timing and duration of selected flower bud phenological stages of two southern highbush blueberry (SHB) cultivars in a Mediterranean climate to optimize the management of commercial production systems. The experiment was conducted in commercial orchards during the 2020 growing season, in the Hex River and Wolseley production areas, Western Cape, South Africa. The timing (date) and duration (days) of selected flower bud stages were recorded on individual plants, from April to November 2020 for bud swell, bud break, tight cluster, closed flower, open flower, petal fall, green fruit, colouring fruit, and fruit harvest respectively. Standard commercial management practices were followed on both sites. Cultivar 8-42 flowered from April to mid-October, with a peak during early August. Cropping occurred from early August to mid-November, and volumes peaked in October, at both sites. Cultivar 9-02 flowered from April to late October, with a peak during early August at the Wolseley site, whereas flowering for this cultivar only peaked during late September, at the Hex River site, indicating a possible climate related response. Subsequently, harvest started two weeks later at the Hex River site for ‘9-02’, while the highest yield volumes were obtained during October to early November, at both sites. This paper provides a first report on the phenological categorization of the reproductive development of commercial SHB blueberry cultivars, as produced in the Western Cape, South Africa. As all major management decisions in blueberry cultivation depend on the phenological phases of the crop, this information will contribute towards decision making regarding production, but also via quantifying the progression of each stage in addition to the peaks, allowing for additional logistical management. The influence of growing conditions on the phenological development of these cultivars was also explored and indicated the need for supplemental research considering the influence of micro-environmental conditions in driving evergreen production blueberry systems.

Efficient Transient Expression for Functional Analysis in Fruit Using the Tsukuba System Vector

Evaluating the function of genes expressed in fruit tissues of fruit tree species using a genetic transformation approach is a long process because the trees are generally recalcitrant to genetic transformation and cannot bear fruit during their long juvenile phases. Transient gene expression in fruit enables the functional analysis of genes associated with fruit traits, which may accelerate the study of fruit physiology. Here, by using the recently developed “Tsukuba system”, we successfully established an efficient transient expression system in harvested fruit tissues. The “Tsukuba system” utilizes a combination of the geminiviral replication system and a double terminator, which ensures sufficient levels of transgene expression. We used blueberry fruit as a model to characterize the applicability of this system for transient expression in fruit tissue. The pTKB3-EGFP vector was introduced by agroinfiltration into the fruit tissues of several blueberry cultivars. We found that transient GFP fluorescence in fruit peaked 4–6 days after agroinfiltration. Agrobacterium suspensions were easily injected into soft, mature fruit, and GFP was strongly expressed; however, hard, immature fruit were not penetrable by Agrobacterium suspensions, and GFP was rarely detected. We then tested the applicability of the developed system to other fruit tree species: six families, 17 species, and 26 cultivars. GFP fluorescence was detected in all species, except for Japanese apricot. In blueberry, bilberry, sweet cherry, apricot, and satsuma mandarin, GFP was highly expressed and observed in a large proportion of the flesh. In kiwifruit, hardy kiwifruits, persimmon, peach, apple, European pear, and grape, GFP fluorescence was limited to certain parts of the fruits. Finally, transient VcMYBA1 overexpression in blueberry was tested as a model for gene functional analysis in fruit. Transient VcMYBA1 overexpression induced red pigmentation in the flesh, suggesting that VcMYBA1 expression caused anthocyanin accumulation. This study provides a technical basis for the rapid evaluation of genes expressed in fruit, which will be useful for gene function evaluation studies in fruit crops with long juvenile phases.

Agricultural Water Footprint of Southern Highbush Blueberry Produced Commercially with Drip Irrigation and Sprinkler Frost Protection

A study was conducted from 2010 to 2017 to determine the water footprint for producing blueberries in the Entre Ríos province of Argentina. Three cultivars of southern highbush blueberry (hybrid cross of Vaccinium sp.) were evaluated in the study, including “Star”, “Emerald”, and “Snowchaser”. In each case, the plants were irrigated by drip and protected from frost using overhead sprinklers. Water requirements for irrigation and frost protection varied among the cultivars due to differences in the timing of flowering and fruit development. The annual water footprint for fruit production in each cultivar is expressed in units of cubic meters of water used to produce one ton of fresh fruit and ranged from 212 - 578 m3∙t−1 for “Star”, 296 - 985 m3∙t−1 for “Emerald”, and 536 - 4066 m3∙t−1 for “Snowchaser”. “Snowchaser” flowered earlier than the other cultivars and, therefore, needed more water for frost protection. “Star”, on the other hand, ripened the latest among the cultivars and required little to no water for frost protection. Frost protection required a minimum of 30 m3∙h−1 of water per hectare and in addition to drip irrigation was a major component of the water footprint.

Relationship between fruit firmness and dry matter in three blueberry (Vaccinium corymbosum L.) cultivars grown in different agroclimatic zones

Relationship between fruit firmness and dry matter in three blueberry (<i>Vaccinium corymbosum</i> L.) cultivars grown in different agroclimatic zones

A Review of Botryosphaeria Stem Blight Disease of Blueberry from the Perspective of Plant Breeding

Stem blight of blueberry caused by fungal pathogens in the family Botryosphaeriaceae presents a major challenge to global blueberry production. Since its first documented outbreak in North Carolina, USA in the 1950s, Botryosphaeria stem blight has been reported in the blueberry production regions of more than nine countries across five continents. The lack of effective management strategies or resistant cultivars makes disease control especially challenging. With the goal of illuminating directions for future Botryosphaeria stem blight management, especially through resistant-cultivar development, this review summarizes the latest information on the distribution and causal pathogens of this disease, the pathogenicity of fungal species, disease resistance of blueberry cultivars, and currently recommended management practices. DNA sequencing techniques have revealed multiple fungal species that are associated with this disease. However, a lack of reliable methods to screen cultivars for stem blight resistance remains a major bottleneck for the development of resistant cultivars. Future studies should focus on at least four key areas: (1) the development and adoption of uniform and reliable screening protocols; (2) utilization of diverse and well-characterized Botryosphaeriaceae isolates for germplasm screens; (3) field evaluations of cultivar resistance and management practices; and (4) exploration of new tools for disease management and prevention.

EVALUATION OF NEW BLUEBERRY CULTIVARS IN PEDOCLIMATIC CONDITIONS FROM RIFG PITESTI-MARACINENI

Vaccinum corymbosum is one of the species highly valued for the taste and dietary value of its berries. The new blueberry cultivars obtained in the breeding activity have high productivity, resistance to diseases and pests, and large and easily removable fruits. The success of the extension of blueberry crops depends on the adaptability of the cultivars to soil conditions and regional climate changes. A study was carried out at the Research Institute for Fruit Growing Pitesti-Maracineni, in the period 2019-2022, and was focused on the vegetative growth and fruiting processes, berries quality, and evaluated the disease and pest behavior of 13 new blueberry cultivars, currently in their 4th year ('Top Shelf', 'Blue Ribbon', 'Calypso' and 'Valor'), respectively 6 years from planting ('Duke', 'Bluejay', 'Draper', 'Liberty', 'Elliott' and 'Aurora'). The ripening period of the new cultivars covered a period between the second decade of June (12.06.2020, 'Duke') and the end of August (27.08.2021, 'Aurora', 'Last Call' and 'Elliott'). Depending on the age of fruit ripening, the cultivars were divided into very early ('Duke'), early ('Huron'), early-middle ('Blue Ribbon', 'Draper', 'Bluejay'), middle ('Top Shelf', 'Valor', 'Calypso'), late ('Cargo' and 'Liberty') and very late ('Last Call', 'Elliott' and 'Aurora'). At the end of the four years of study, the analysis of the data recorded for the vegetative growth and fruiting processes indicated that, for the younger plants (4th year after planting), for an average bush volume of 0.41m3 (0.14- 0.84 m3) berry yield fluctuated around 7.27 t/ha (1.66-16.59 t/ha). The cultivars with superior vigor were 'Valor', 'Last Call', and 'Cargo' (0.49-0.53 m3), the most productive being 'Cargo', with approximately 13.6 t /ha. For blueberry in the 6th year after planting, where the average volume of the bush was 0.53 m3 (0.19-0.82 m3), the fruit production was 6.89 t/ha (1.87 -14.4 t/ha). The cultivars with superior vigor were 'Bluejay', 'Aurora' and 'Liberty' (0.59-0.62 m3), and in terms of productivity, 'Duke' (9.13 t/ha) and 'Liberty' stood out (9.92 t/ha). For plants of the same age (3 and 4 years after planting), the average berry weight fluctuated around 2.25 g (0.7-5.72 g), the firmness recorded an average of 43.95 (15.9-77.50 units), while juice pH and total soluble substance content showed average values of 3.44 (2.24-5.72) and 13.32˚Brix (7.9-23.40). The highest berry weight was determined for 'Top Shelf' cultivar (2.9 g). The cultivars 'Aurora' and 'Last Call' stood out for their superior content of total soluble solids (17.14 and 16.01˚Brix), and the cultivars 'Blue Ribbon' and 'Top Shelf' for their high fruit pH (4.18 and 3.69). Last but not least, the high firmness of the fruits highlighted the Aurora and 'Blue Ribbon' cultivars (57.90 and 52.28 HPE-II-FFF Bareiss units). Regarding the phytosanitary status of the studied shrubs, increased sensitivity to diseases of the 'Huron' cultivar was highlighted (ISV 2.9%), especially to the attack of Phytophthora spp. (1.6%attack degree), which influenced significantly plant survival. At the end of the study period, we can recommend the cultivars 'Duke', Liberty', and 'Cargo' for cultivation in similar pedoclimatic conditions, the first standing out for its earliness and productivity, and the last two for their high fruit production.

Efficient micropropagation protocol of three cultivars of highbush blueberry (Vaccinium corymbosum L.)

Highbush blueberry (Vaccinium corymbosum L.) is increasingly farmed for its nutritional and health benefits, but high yield and fruit quality require proper planting material. Modified Murashige and Skoog (MW), Anderson’s Rhododendron (AN), and Woody Plant Medium (WPM) were compared for in vitro organogenesis and rooting of three highbush blueberries ‘Elizabeth’, ‘Meader’, and ‘Liberty’. All media contained 0.1 mg L-1 zeatin applied with a combination of IBA, IAA, and GA3. The results showed that MW medium is more suitable for in vitro multiplication of ‘Elizabeth’ and ‘Meader’, and WPM medium for ‘Liberty’. However, medium supplemented with a low concentration of IBA (≤ 0.4 mg L-1) and 0.1 mg L-1 zeatin increased the shoot regeneration rate of highbush blueberries multiplied in vitro. The rooting capability was studied by using WPM and AN medium with IBA and IAA with zeatin. The highest rooting rate (85%) and acclimatization (70%) were achieved in ‘Liberty’, and the lowest was in ‘Elizabeth’ (33.3% and 50%, respectively) and ‘Meader’ (33.3% and 43.8%, respectively). Rooted plantlets developed good quality roots and were transplanted into peat:perlite (4:1) substrates and acclimatized in a greenhouse under controlled conditions. We developed a complete micropropagation protocol for cvs. ‘Meader’, ‘Elizabeth’ and ‘Liberty’ blueberry. This protocol can be used for the production of certified vegetative material or different biotechnological purposes.

Comprehensive resistance evaluation of 15 blueberry cultivars under high soil pH stress based on growth phenotype and physiological traits.

High soil pH is one of the main abiotic factors that negatively affects blueberry growth and cultivation. However, no comprehensive evaluation of the high soil pH tolerance of different blueberry cultivars has been conducted. Herein, 16 phenotypic and physiological indices of 15 blueberry cultivars were measured through pot experiments, and the high-pH soil tolerance coefficient (HSTC) was calculated based on these indices to comprehensively evaluate the high-soil-pH tolerance of plants. The results demonstrated that high soil pH stress inhibited blueberry 77.growth, and MDA, soluble sugar (SS), and soluble protein (SP) levels increased in leaves. Moreover, in all cultivars, CAT activity in the antioxidant system was enhanced, whereas SOD activity was reduced, and the relative expression levels of the antioxidant enzyme genes SOD and CAT showed similar changes. In addition, the leaf chlorophyll relative content (SPAD), net photosynthetic rate (Pn), transpiration rate (E), and stomatal conductance (Gs) decreased, while changes in the intercellular CO2 concentration (Ci) were noted in different cultivars. Finally, according to the comprehensive evaluation value D obtained from the combination of principal component analysis (PCA) and membership function (MF), the 15 blueberry cultivars can be divided into 4 categories: high soil pH-tolerant type ['Briteblue' (highest D value 0.815)], intermediate tolerance type ('Zhaixuan 9', 'Zhaixuan 7', 'Emerald', 'Primadonna', 'Powderblue' and 'Chandler'), low high soil pH-tolerant type ('Brightwell', 'Gardenblue', 'Plolific' and 'Sharpblue') and high soil pH-sensitive type ['Legacy', 'Bluegold', 'Baldwin' and 'Anna' (lowest D value 0.166)]. Stepwise linear regression analysis revealed that plant height, SS, E, leaf length, Ci, SOD, and SPAD could be used to predict and evaluate the high soil pH tolerance of blueberry cultivars.

Leaf Tissue Macronutrient Standards for Northern Highbush Blueberry Grown in Contrasting Environments

Leaf tissue testing is a useful tool for monitoring nutrient requirements in northern highbush blueberry (Vaccinium corymbosum L.; abbreviated as "blueberry") but may require adaptation to specific growing environments. The objective of this study was to evaluate macronutrient concentrations in early-, mid-, and late-season blueberry cultivars grown in two contrasting environments, specifically eastern and western Washington. Climate and soil conditions between these two regions differ tremendously with eastern Washington being more arid with naturally calcareous soils lower in soil organic matter. Sampling was conducted over a 3-year period in commercial fields. Leaf tissue nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S) concentrations were affected by year (Y), growing region (R), cultivar (C), and Day of Year (DOY) that the samples were collected with many interactions. Leaf nutrient concentrations were higher, on average, in western than eastern Washington except for Ca and Mg, indicating sufficiency levels should differ between these regions. Leaf macronutrients generally stabilized between DOY 212-243 (1-31 August), suggesting this period is optimal for tissue sampling. Findings from this study demonstrate the importance of considering regional effects and may be applicable for blueberry cultivated in similar pedo-climactic conditions around the world.

Influence of harvest method on the quality and storage of highbush blueberry

Blueberry quality is one of the most important elements that needs to be evaluated when automatisation processes, such as harvest automation, occur along the supply chain. The aim of this work was to evaluate the suitability of two blueberry cultivars, of new introduction for the area of study, to the mechanical harvest. Particularly the influence of harvest method was evaluated on the quality of cv. Cargo® and Top Shelf® for a short storage time (max. 28 days) in normal atmosphere assuming so an immediate sale of blueberries. Samples mechanically harvested were compared in terms of qualitative performance with samples manually picked throught two activity carried on two years. In the activity 1 a preliminary laboratory test simulation of mechanical harvest was carried on to evaluate the attitude of both cultivars to the automatisation process and the berries were evaluated immediately after the harvest time. The activity 2 was aimed to evaluate the quality of berries mechanically harvested in field and after the storage process at 2 ± 1 °C and 90% RH in a cold room for 28 days under normal atmospheric conditions (NA). The higher percentage of shrivelled berries for the simulation of mechanical harvest samples (SEH) (activity 1) and berries harvested with the Easy Harvester machine® (EH samples) (activity 2) in the post-harvest period was probably due to the low % of pruin on berries skin content at the harvest time (0 days). All samples although achieved a quality assessment equivalent to still marketable berries after 28 days of storage. TSSC were significantly higher in the EH group for both years. TSSC and TA were higher in Cargo® than in Top Shelf®. In general the automatisation of the harvesting process did not significantly affect blueberry quality after storage. • This work highlights how the way of harvest can affect the quality of fruits during the storage time. • New blueberry cultivar ( ‘Cargo’® and ‘Top Shelf’®) for the market are evaluated in this studies; limited studies are reported on these cultivars. • Limited studies are reported on the mechanized harvest on blueberries in Italy

Physiological and metabolic responses to aluminum toxicity reveal differing resistance mechanisms to long-term exposure in highbush blueberry cultivars

Aluminum (Al) toxicity is a major environmental stress that affects the growth and development of plants in acid soils. Plants have developed different mechanisms and strategies of Al resistance based on the biosynthesis of organic compounds and the formation of non-phytotoxic complexes with Al. In this study we use three cultivars traditionally cultivated of highbush blueberry (Vaccinium corymbosum L., ‘Brigitta’, ‘Star’, and ‘Duke’) and two cultivars from the USA (‘Camelia’ and ‘Cargo’) that were recently introduced in southern Chile. Physiological and biochemical parameters were evaluated on plants grown at 0 and 200 µM Al in Hoagland solution (pH 4.5) for 0, 7, 14, and 21 days. We found that the Al concentration increased in roots and shoots in all cultivars and that the relative growth rate was reduced only in shoots of ‘Star’ plants, an Al-sensitive cultivar. Photosynthetic parameters were reduced under Al treatment only in ‘Star’ and ‘Brigitta’. The concentration of photosynthetic pigments was reduced in ‘Star’, but increased in ‘Cargo’ and ‘Brigitta’ under Al toxicity. ‘Duke’ had a higher concentration of sugars and polyphenols, increased antioxidant activity, and low lipid peroxidation in leaves under Al treatment. The levels of ascorbate (ASC) and dehydroascorbate (DHA) increased in ‘Camellia’ leaves and Duke roots. The ASC/DHA ratio in roots increased in ‘Star’, and ‘Camellia’, but decreased in ‘Duke’ and ‘Brigitta’ leaves in the Al treatment. Cultivars ‘Cargo’ and ‘Brigitta’ increased oxalate exudation from roots under Al-toxicity, whereas ‘Star’ had low oxalate exudation. The results suggest a possible strategy related to internal detoxification via carbohydrates and phenolic compounds to reduce the long term toxic effect of Al in ‘Duke’, ‘Cargo’, and ‘Camellia’ cultivars of V. corymbosum under acidic conditions.

Hummingbirds, honeybees, and wild insect pollinators affect yield and berry quality of blueberries depending on cultivar and farm’s spatial context

The contribution of wild pollination service to global agriculture is increasingly recognized. Still, biotic pollination demand is mainly covered by managed species, whereas implementing ecological intensification practices to promote wild pollination service remain less common. In this study, we evaluated (i) the effect of wild and managed pollinators and the richness of pollinator functional groups (RPFG) on production quality (i.e., fruit size) and quantity (i.e., crop yield), of two southern highbush blueberry (Vaccinium corymbosum) cultivars, and (ii) how wild pollinator service and crop production correlate with farm’s land cover. We found that pollination service supply and the spatial context interact with the blueberry cultivar to determine yield and fruit size. The abundance of big-sized wild bees and hummingbirds positively affected fruit size and crop yield, but the relationship's significance was cultivar-dependent. In contrast, the increase in honeybees visitation rate was detrimental to the average fruit size of blueberries, but the effect was not generalizable between cultivars. The amount of forested area affected positively wild pollinator abundance and RPFG only in one cultivar, whereas grassland and hedgerow had adverse effects for pollinators in the other. Consistently, the relation between blueberry fruit size and the farm’s land cover was subordinate to the cultivar. That is, despite all significant relations had the same sign between cultivars, their coefficients were statistically different. Our results support the idea that wild pollinators contribute to producing higher yields and larger berries in blueberry crops. Moreover, we found that the retention of natural forest at a 200 m radius within the farm may increase pollination service supply. However, the significance of every effect was contingent on the blueberry cultivar. This cultivar-dependent response points out that a robust assessment of pollinator benefits not only should include multiple production metrics, but also must incorporate within-crop variation, particularly in systems where growers use a mosaic of cultivars with different pollination requirements.

Identification of MicroRNAs Related to Phytohormone Signal Transduction and Self-incompatibility of Rabbiteye Blueberry Pollen

MicroRNAs (miRNAs) related to phytohormone signal transduction and self-incompatibility may play an important role in the xenia effect. However, associated research in this area is still lacking in rabbiteye blueberry (Vaccinium ashei). In this study, we identified miRNAs, predicted their target genes, performed functional enrichment analysis of the target genes, and screened for miRNAs related to phytohormone signaling and self-incompatibility. A total of 491 miRNAs were identified, of which 27 and 67 known miRNAs as well as 274 and 416 new miRNAs were found in the rabbiteye blueberry cultivars Brightwell and Premier, respectively. Compared with ‘Premier’, 31 miRNAs were upregulated and 62 miRNAs were downregulated in ‘Brightwell’. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analysis indicated that the 4985 target genes predicted were involved in biosynthesis of amino acids, plant–pathogen interaction, and spliceosome pathways. A total of 10, one, one, five, two, five, and two candidate miRNAs related to auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, and salicylic acid signaling, respectively, in rabbiteye blueberry pollen were identified. Further analysis indicated that novel_miR_49 was a candidate miRNA related to self-incompatibility, and their target gene was maker-VaccDscaff21-snap-gene-21.37. In addition, the KEGG enrichment analysis of the target genes of novel_miR_49 showed that they were involved in the ribosome, aminoacyl-tRNA biosynthesis, and glycosylphosphatidylinositol-anchor biosynthesis pathways. The results revealed that the microRNAs of rabbiteye blueberry pollen regulated to phytohormone signal transduction and self-incompatibility signal transduction based on related to auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, and salicylic acid signaling. Results suggest that more research of the effects of miRNAs on regulation of hormone signal transduction and self-incompatibility is necessary for elucidating the molecular mechanism of the xenia effect.

Influence of Fertigation and Granular Applications of Potassium Fertilizer on Soil pH and Availability of Potassium and Other Nutrients in a Mature Planting of Northern Highbush Blueberry

Although northern highbush blueberry (Vaccinium corymbosum L.) fields are often fertigated using soluble or liquid fertilizers, recommendations for applying most nutrients to the crop, including K, are based on the use of granular fertilizers. The objective of the present study was to compare fertigation to granular application of K in a mature planting of Duke, a popular early season blueberry cultivar that ripens from June through July in Oregon and Washington. The plants were grown on raised beds and irrigated using two lines of drip tubing per row. Treatments were initiated in 2016 and included no K fertilizer, a single application of granular potassium sulfate (K2SO4) in April, and fertigation once a week from April to August with soluble K2SO4 or liquid potassium thiosulfate (K2S2O3). Each treatment was applied for 2 years at a total rate of 70 kg·ha−1 K per year. The plants were also fertigated with 168 and 224 kg·ha−1 N in 2016 and 2017, respectively, and 30 kg·ha−1 P per year. Although extractable soil K was initially low at the site (144 mg·kg−1), the treatments had no effect on plant dry weight, yield, fruit quality, or the concentration of K in recently expanded leaves. However, during the first year of the study, K fertigation with K2SO4 or K2S2O3 reduced soil pH and increased the concentrations of K+, Ca2+, Mn2+, and SO42− in the soil solution under the drip emitters compared with no K or granular K2SO4, whereas granular application of K2SO4 resulted in higher concentrations of K+ between the emitters than any other treatment. Fertigation also affected the concentration of K in the fruit during the first year, although in this case, the concentration was lower with K fertigation than with no K or granular applications of K2SO4. During the second year, fertigation and granular K continued to result in higher concentrations of K+ in soil solution under and between the drip emitters, respectively, but at this point, extractable soil K was higher with each of the K fertilizers than with no K. Consequently, the concentration of K in leaves sampled from entire plants in late September that year was higher with any of the K fertilizers than with no K. Potassium fertilization also altered concentrations of other nutrients in the plants, including Mg, S, B, Cu, and Mn in the leaves; Ca, Mg, and B in the fruit; Mn and Zn in the woody canes; and P, Mg, S, and Mn in the crown. In many cases, concentrations of these nutrients were higher with one or more of the K fertilizers than with no K. Thus, regardless of the application method, K2SO4 and K2S2O3 appear to be good sources for increasing availability of K and other nutrients in the plants and soil. However, the amount of K in the plants was sufficient at the site, and therefore, none of the fertilizers provided a short-term benefit to growth or fruit production in the present study.

The Influence of Variety and Climatic Year on the Phenology of Blueberry Grown in the Banat Area, Romania

This paper’s aim was to investigate the influence of variety and the climatic year on vegetation phenophases in blueberries grown in southwest Romania, the Banat region. This study was carried out during the growing season of 2020–2022 in a blueberry plantation, for ‘Duke’, ‘Hannah’s Choice’ and ‘Elliott’ varieties. In the study, phenological traits were recorded using the BBCH phenological scale and the observation of phenotypic data was recorded as in Julian days. Thus, it is found that the duration of each phenophase characterized each variety. The calendar periods for the onset of vegetation and the duration of spring phenological development stages in varieties have differed from year to year and depended on weather conditions. In the case of the phenological stage, depending on variety, the maximum amplitude was recorded for BBCH 87 stage (75% blue fruits) of 51 days, and the minimum amplitude, of 25 days, for BBCH 51 stage (bud swell) and BBCH 59 (late pink bud). The coefficient of variation, depending on climatic year, for generative phenophases, had values between 6.5% (BBCH 67-petal fall) and 21.1% (BBCH 51-bud swell). It was found that the variety and the climatic year influence the development of vegetation phenophases. The results indicate that blueberry cultivars have demonstrated a high degree of phenotypic plasticity to respond to gradual changes in environmental conditions and are important for the evaluation of cultivar cultivation prospects in the studied area.

Phytochemical screening and antioxidant capacity of two berry cultivars, ‘Ruben’ and ‘Duke’, depending on their harvesting time

Commercial berry production is an attractive industry worldwide, including in Romania because berries are a rich source of bioactive compounds with antioxidant capacity, thus becoming the most important functional and nutraceutical foods in our diet. The aim of our work was to characterize two different species, Saskatoon berry (Amelanchier alnifolia Nutt., Rosaceae) and blueberry (Vaccinium corymbosum L., Ericaceae), from the point of view of total phenols and anthocyanin as well as of antioxidant capacity depending on their harvesting time. The analyzed cultivars ‘Ruben’ and ‘Duke’ were cultivated in the North-West of Romania, the first cultivar has been officially introduced in Romania in 2018. The results show that ‘Ruben’ cultivar is richer in bioactive compounds compared with ‘Duke’ cultivars. The level of total phenols of ‘Ruben’ cultivar was 297.937 ± 4.30 and 347.412 ± 14.13 mg GAE/100 g fw (fresh weight) at early and full ripening time, respectively. The highest anthocyanins content was found in ‘Ruben’ cultivar (410.659 ± 52.88 mg/100 g fw) at full ripening time. Also, the high values of antioxidant capacity determined by four different methods (DPPH, FRAP, ABTS, CUPRAC) was recorded in the case of cultivar ‘Ruben’. Both blueberry cultivars ‘Duke’ and ‘Ruben’ are rich sources in bioactive compounds such as phenolics, especially anthocyanins. The blueberries harvested at full ripening period provided the highest level of total phenols and anthocyanins compounds. These compounds act as powerful antioxidants and thus they could improve the health status of the human body, or can be used by food and nutraceutical manufacturers.

Southern Highbush Blueberry Cultivars from the University of Florida

This publication provides historical background on southern highbush blueberries (SHB), and information on specific UF/IFAS cultivars that can be a helpful resource for SHB growers. Written by D. A. Phillips, J. G. Williamson, P. M. Lyrene, and P. R. Munoz, and published by the UF/IFAS Horticultural Sciences Department, revised September 2022.

Effect of explant type, culture medium, and BAP concentration on in vitro shoot development in highbush blueberry (Vaccinium corymbosum L.) cultivars

Effect of explant type, culture medium, and BAP concentration on in vitro shoot development in highbush blueberry (Vaccinium corymbosum L.) cultivars

Reduced-input Pruning Methods Are a Viable Option for Machine-harvested ‘Mini Blues’ Highbush Blueberry

‘Mini Blues’ highbush blueberry (Vaccinium sp.) was released in 2016 as a high-quality, machine-harvestable alternative to lowbush (V. angustifolium Ait.) or other small-fruited highbush blueberry cultivars for processed markets. A planting was established in Oct. 2015 in western Oregon to evaluate the effects of pruning method on yield, machine-harvest efficiency (MHE), berry weight and total soluble solids (TSS), leaf tissue nutrients, pruning weight, pruning time, and costs. Plants were pruned for shape and to remove flower buds in 2015–16 and 2016–17. Pruning treatments began in 2017–18 and included: 1) conventional highbush pruning (HB); 2) removing one or two of the oldest canes per bush (Speed); 3) leaving plants to grow from 2017 to 2021 (Unpruned) before doing a hard renovation prune in 2021–22 (cutting the plants back to a height of ≈0.3 m and leaving the best 8–10 canes/plant); and 4) hedging after fruit harvest in 2018 (Hedge) and then unpruned afterward until renovation in 2021–22. The pattern of yield progression, observed wood aging, and reduced berry size after 4 years of no pruning indicated renovation was necessary in the unpruned and hedge treatments. Low growth was removed each year in all treatments, and hedging was only done in 2018 because it severely reduced yield the following year and, therefore, was not a viable option. An over-the-row machine harvester was used from 2018 to 2021. Speed-pruned plants, averaged over 4 years, had the greatest potential yield (3.75 kg/plant) compared with the other treatments (averaged 2.99 kg/plant) but had a similar yield as HB because more fruit remained on the bush after harvest with speed pruning. In 2021, speed pruning resulted in the highest yield (4.2 kg/plant), followed by HB (3.8 kg/plant) and the unpruned and hedge methods (averaged 3.1 kg/plant). MHE increased from 43% in 2018 to 74% in 2021, mainly because, as the plants aged, a larger proportion of the canopy was above the catcher plates on the harvester. On average, MHE was highest with HB pruning (70%), intermediate in the unpruned and speed-pruned plants (59%), and lowest in the hedged plants (49%). In 2021, ground drop loss was highest for hedge (18%), lowest for speed (14%), and intermediate for HB and unpruned (averaged 16%) methods. HB-pruned plants had heavier berries (0.64 g) than unpruned and hedge treatments (averaged 0.57 g) and a similar berry weight as the speed-pruned plants (0.61 g). Pruning had no effect on berry TSS. In contrast to leaf K, leaf Mg and Ca concentrations were lowest in HB and higher in all other treatments. In 2020–21, HB pruning required 471 h·ha−1, while speed pruning took 79 h·ha−1; the hedge and unpruned treatments required an average of 60 h·ha−1 to remove low-growing branches that would interfere with machine harvest. In 2021–22, renovation of the unpruned and hedge treatments took 290 h·ha−1. While leaving bushes unpruned during establishment appears to be a promising option for ‘Mini Blues’, further work is needed to evaluate fruit production after renovation and to determine how long the plants could remain unpruned thereafter. Speed pruning is also a good option, reducing pruning costs by 85%.

Identification and quantification of anthocyanins of 62 blueberry cultivars via UPLC-MS

Blueberries are rich in anthocyanins, which are plant-specific secondary metabolites that are a good source of plant nutrients. Although anthocyanins have been investigated, there is a lack of comprehensive detailed research that includes large numbers of blueberry cultivars, and the anthocyanin compositions of some cultivars are still unknown. Consequently, we determined the anthocyanin compositions of 62 cultivars using ultra-performance liquid chromatography–mass spectrometry (UPLC–MS). In total, we identified 30 anthocyanins derived from five kinds of anthocyanidin. We also identified four glycosides having three kinds of modifications. Among the tested cultivars, ‘Rubel’ contained the highest anthocyanin content, at 534.158 mg/100 g fresh weight (FW), whereas ‘Puru’ contained the lowest anthocyanin content at 71.734 mg/100 g FW. ‘Malvidin-gal’ had the highest average content among all the anthocyanin monomers, at 48.95 mg/100 g FW. ‘HL9’ had the greatest methylation degree, at 79.39%, and ‘HL2’ had the greatest acetylation degree, at 25.14%. This study provides detailed anthocyanin compositions and modifications of different blueberry cultivars. These data will aid in breeding high-quality blueberry cultivars and in developing related healthy functional foods.