Blueberry Plants Research Articles

Relationship between cane age and vegetative and reproductive traits of northern highbush blueberry in Chile and United States

Blueberry fruit yield increases with cane diameter. To optimize field management, it is necessary to understand the relationship between cane age, cane diameter, and the vegetative and reproductive expressions of the plant. Trials were conducted in two sites: 1) Linares, Maule, Chile (35°51′S, 71°36′W) in ‘Duke’ and ‘Brigitta’ (fourteen-year-old plants); and 2) Gobles, Michigan, USA (42°22′N, 85°54′W) in cv. ‘Duke’ (fifteen-year-old plants) and ‘Brigitta’ (nineteen-year-old plants). At each site, canes of different diameters (0.4 to 4 cm) were selected and measured for cane diameter and length, number of annual wood growth rings (cane age), number of flower buds per cane and of flowers per bud, and number and total length of the shoots. Cane diameter and cane age were positively and linearly associated for both cv. ‘Brigitta’ (r2=0.93 and 0.91 in Chile and USA, respectively; P<0.0001) and ‘Duke’ (r2=0.86 and 0.92 in Chile and USA, respectively; P<0.0001). For ‘Duke’, total shoot length was the vegetative variable most closely associated with both cane diameter (Chile, r2=0.74; USA, r2=0.80; P<0.001) and cane age (Chile, r2=0.68; USA, r2=0.72; P<0.0001). For ‘Brigitta’, the determination coefficients between total shoot length and cane diameter (Chile, r2=0.55; USA, r2=0.76; P≤0.001) and age (Chile, r2=0.50; USA, r2=0.47; P<0.05) were positive but lower. The number of flower buds per cane was linearly and positively associated with cane diameter and cane age for both cultivars and countries (r2=0.45-0.62; p<0.0001). The associations between cane age and diameter with the other vegetative and reproductive variables varied between both countries and cultivars (Chile, r2=0.69-0.01; USA, r2=0.84-0.02). Our results show that cane age and diameter are highly associated and can be used to assess various vegetative and reproductive traits in highbush blueberry plants. Consistently across cultivars and sites, the data shows that as canes aged and growth rings are added, they increased in diameter, total shoot length, number of shoots, number of flower buds and cane length. This information could be useful to estimate yield and define pruning practices in adult blueberries.

Benzothiadiazole enhances ascorbate recycling and polyphenols accumulation in blueberry in a cultivar-dependent manner.

Benzothiadiazole (BTH) is a functional analogue of salicylic acid able to induce systemic acquired resistance in many horticultural crops. The aim of the work was to investigate how BTH may affect i) fruit quality, ii) ascorbic acid (AsA) oxidation and recycling metabolism and iii) phenolic compounds accumulation, during development and ripening of berries from the two selected cultivars. Blueberry (Vaccinium corymbosum L.) plants (cv 'Brigitta' and 'Duke') were treated with 0.118 mM BTH every two weeks during ripening, then all fruits of each plant were harvested and divided in four developmental stages. Results indicated that BTH had no marked effects on fruit quality parameters. During the first developmental stage, BTH negatively affected dry matter in both cv, while soluble solids and AsA content were affected in 'Duke'. In fully ripe berries, BTH reduced dry matter in 'Duke' and enhanced soluble solids content in 'Brigitta', while diminishing titratable acidity. AsA content was positively affected by BTH in 'Duke', but not in 'Brigitta'. The effect of BTH on the enzymes involved in AsA recycling was recorded in berries at the third (fruit more than half pigmented) and fourth developmental stages. After treatment, in both cv ascorbate peroxidase (APX) activity increased in fully ripe berries, while monodehydroascorbate reductase (MDHAR) activity was stimulated at the third ripening stage. Conversely, the activities of dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were enhanced only in 'Brigitta' and in 'Duke', respectively. BTH stimulated total polyphenols, flavonoid and anthocyanin accumulation in 'Brigitta' and in 'Duke' at the third and fourth ripening stages. In fully ripe berries, BTH enhanced the accumulation of delphinidins, cyanidins, petunidins and peonidins in 'Brigitta', while in 'Duke' it increased all classes of anthocyanidins, including malvidin. On the contrary, the relative proportion of the individual anthocyanins was only slightly affected by BTH treatment, mainly regarding delphinidin and malvidin at the third and fourth stage of ripening of 'Duke' and 'Brigitta', respectively. These results show that preharvest BTH application can positively impact on fruit bioactive compounds levels, affecting AsA recycling and content and increasing polyphenols accumulation in fruit, but partly depending on cv and ripening stage.

Integrated Physiological and Metabolomic Analyses Reveal the Differences in the Fruit Quality of the Blueberry Cultivated in Three Soilless Substrates.

With improving living standards, traditional blueberry planting modes cannot meet commercial demands, and blueberry cultivation with soilless substrate has become a popular solution in the blueberry industry. In this study, different soilless substrate treatments were found to markedly influence fruit appearance and intrinsic quality. The fruit in the 50:50 peat/pine bark (v/v) (FPB) treatment group had the maximum single fruit weight, largest vertical diameter, and brightest color, as well as the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) value, solid-acid ratio and anthocyanin content. The fruit in the 50:50 pine bark/rice husk (v/v) (FBR) treatment group had the highest total phenol and flavonoid levels, largest drip loss value, and lowest total pectin content and firmness value. Metabolomic analysis showed that flavonoid, carbohydrate, and carbohydrate conjugate, and amino acid, peptide, and analog levels were significantly different between groups. Fruit in the FPB group had the highest sucrose, D-fructose 1,6-bisphosphate, salidroside, tectorigenin, naringenin chalcone, trifolirhizin, and galangin contents. The increase in the relative expression of phenylalanine (Phe) promoted the synthesis of fruit polyphenols in the FBR group. Our results provide new insights into the effects of different substrates on the quality of blueberries and a reference for the soilless substrate cultivation of blueberries.

Biodiversity of Fungi Inhabiting European Blueberry in North-Western Russia and in Finland

European blueberry is a common plant in coniferous and mixed forests that grows in Russia, Northern Europe, Asia, United States, and Canada. Among the fungi that cause blueberry diseases, the most harmful are Diaporthe vaccinii and Colletotrichum acutatum. These fungi are included in the consolidated list of quarantine objects of the Eurasian Economic Union and their occurrence and spread in the territory of countries of this Union is subject to strict control. Most taxa of micromycetes, particularly, Diaporthe and Colletotrichum species, can be correctly identified to the species level based on solely molecular phylogenetic features. The aim of the present work was to assess the biodiversity of fungi associated with blueberry growing in North-Western Russia and in Finland using morphological and molecular genetic features. Altogether, the study included 17 specimens of wild blueberry exhibiting necrotic spots on leaves and stem lesions that were collected in 2017 in St. Petersburg and in five districts of Leningrad region, as well as in the Republic of Karelia and in Finland. Analysis of the morphological and molecular genetic features of the fungal strains isolated from these blueberry specimens led to identification of 11 species: Boeremia exigua, Colletotrichum salicis, Diaporthe eres, Fusarium avenaceum, F. incarnatum, F. sporotrichioides, Heterophoma sylvatica, Kalmusia longispora, Microsphaeropsis olivacea, Neocucurbitaria cava, and Sporocadus rosigena. There were also fungi representing two sections of the genus Alternaria: Alternaria and Infectoriae, and micromycetes of the genera Chaetomium, Cladosporium, Coniothyrium, Curvularia, Epicoccum, Penicillium, Pestalotiopsis, Sordaria, and Trichoderma. The species Colletotrichum salicis, Heterophoma sylvatica, Kalmusia longispora, Microsphaeropsis olivacea, and Neocucurbitaria cava were for the first time found in Russia. The species Sporocadus rosigena was for the first time detected in Finland. Fusarium avenaceum, F. incarnatum, and F. sporotrichioides were for the first time observed in association with blueberry plants. The species Diaporthe vaccinii and Colletotrichum acutatum included in the consolidated list of quarantine objects of the Eurasian Economic Union were not detected in this study.

Functional analysis of plasma membrane H+-ATPases in response to alkaline stress in blueberry

• At pH 8.0, H + influx and H + efflux were restricted in blueberry roots. • In blueberry roots and leaves, most VcHAs had lowest transcript levels at pH 8.0. • ATP proton pump activity was increased in Arabidopsis over-expressing (OE) VcHAs . • A. thaliana OE lines tolerated alkaline stress due to increased H + pumping. Blueberry ( Vaccinium spp.) favors acid soils (pH 4.0–5.5), but the reasons for this strong preference are unclear. Root plasma membrane proton pumps (PM H + -ATPases - HAs) promote the efflux of hydrogen ions (H + ) and thus promote nutrient absorption, thereby reducing stress associated with alkaline soils. In this study, ‘Jewel’ blueberry ( V. corymbosum ) was grown in media with a range of pH values (pH 5.0, pH 7.0, pH 8.0). After 30 days of growth, the physiological responses and the transcript levels of VcHAs (PM H + -ATPases) were analyzed. Eight VcHA genes were genetically transformed into Arabidopsis thaliana for functional verification. The results showed that (1) blueberry plants grew best at pH 5.0. The root activity at pH 5.0 was more than 1.6 times that at pH 8.0. In the pH 8.0 treatment, H + influx and efflux from blueberry roots were limited. (2) Different VcHA genes showed diverse expression patterns. Among them, VcHA8 was only expressed in the root at pH 5.0. Except for VcHA11.2 in the roots, the transcript levels of VcHAs in roots and leaves were lowest in the pH 8.0 treatment. (3) Transgenic Arabidopsis thaliana plants over-expressing VcHA4.1, VcHA4.2, VcHA4.3, VcHA5, VcHA10.1, VcHA10.2, VcHA11.1, or VcHA11.2 showed stronger root activity than that of wild-type in all pH treatments. The root activity of the line overexpressing VcHA5 was 96 times that of the control. Compared with control plants, the phenotypic analyses of the VcHAs transgenic plants revealed enhanced levels of plant height, leaf size and chlorophyll content. The H + -ATPase activity of Arabidopsis overexpressing VcHA10.2 was 44 times that of the control. VcHAs not only significantly increased the hydrolytic activity and ATP proton pump activity in Arabidopsis but also increased H + efflux, leading to cytoplasmic alkalinization in root epidermal cells. Over-expression of VcHAs significantly increased H + pumping in Arabidopsis roots under alkaline rhizosphere stress, confirming that these genes encode functional proteins that are capable of acidifying the rhizosphere. VcHA10.2 and VcHA5 had the strongest ability to pump H + . The expression of VcHAs was inhibited in blueberry plants growing in high-pH media. This may explain why blueberry grows best in acid soils. These results help to explain why blueberry favors acid soils and may be useful for developing strategies to cultivate this crop in a wider range of soil types.

Analysis and Testing of Rigid–Flexible Coupling Collision Harvesting Processes in Blueberry Plants

China possesses a vast territory, and the manual harvesting of blueberries is time-consuming and labor-intensive. Due to the planting agronomy differences in other countries, China needs to develop a domestic blueberry harvester to realize mechanical blueberry harvesting. In the harvesting process, “collision” is the core problem. Most of the literature has studied rigid body–rigid body collision, while few authors have studied rigid–flexible coupling collision mechanisms in the field of berry harvesting. In this paper, a rigid–flexible coupling collision model between the harvester and the blueberry plant was established based on the L-N nonlinear spring damping model (describing the collision force model between two colliding objects, consisting of the nonlinear spring and the damper) and improved the Coulomb model (the tangential collision force model), and the collision mechanism of blueberry harvesting was analyzed. The harvesting collision process was analyzed using both MATLAB and ADAMS software and the same conclusions were obtained: the collision force and fruit harvesting force were inversely proportional to the machine velocity but positively proportional to the rotational velocity of the hydraulic motor of the harvesting device. The following machine parameters were required to meet harvesting conditions: a harvesting device output rotational velocity of 120–150 r/min and a machine velocity of 40–50 m/min. A harvesting field test using a self-propelled blueberry harvester was conducted, which showed that the test results were consistent with the software simulation conclusions. When the machine velocity of the harvester and the output rotational velocity of the hydraulic motor were 45 m/min and 130 r/min, respectively, the machine provided optimum harvesting efficiency and fruit quality with the following optimum parameters: a harvesting efficiency of 5.1 kg/min, a raw fruit harvesting rate of 2.9%, and a damaged fruit harvesting rate of 3.6%. This research can lay the preliminary theoretical foundation for the analysis of a blueberry harvesting mechanism, and the research results can provide a theoretical reference for the harvesting of other similar berry shrubs.

Insight into the Taxonomic and Functional Diversity of Bacterial Communities Inhabiting Blueberries in Portugal.

Vaccinium myrtillus is a dwarf shrub of the Ericaceae family with a Palearctic distribution, associated with temperate and cold humid climates. It is widespread on the European continent; on the Iberian Peninsula it is located on Atlantic climate mountains and glacial relicts. In Portugal, we find scattered and interesting populations; however, the majority of them are threatened by climate change and wildfires. Given that, the objective of this study is to determine the rhizospheric and root bacterial communities of this plant in the southernmost regions, and, consequently, its potential range and ability to be used as a biofertilizer. In this work, metabarcoding of 16S rRNA gene showed that the endophytic bacterial diversity is dependent on the plant and selected by it according to the observed alpha and beta diversity. Moreover, a culturomic approach allowed 142 different strains to be isolated, some of them being putative new species. Additionally, some strains belonging to the genera Bacillus, Paenibacillus, Pseudomonas, Paraburkholderia, and Caballeronia showed significant potential to be applied as multifunctional biofertilizers since they present good plant growth-promoting (PGP) mechanisms, high colonization capacities, and an increase in vegetative parameters in blueberry and tomato plants.

Functional activity analysis of plasma membrane H+-ATPase gene promoter and physiological functional identification of interactive transcription factor in blueberry

Blueberry plant ( Vaccinium spp.) roots are sensitive to pH changes (> 5.5) in the rhizosphere. In China, the soil pH in blueberry planting areas is typically above 5.5, consequently restricting industry expansion. Root plasma membrane proton pumps (PM H + -ATPase - HAs ) promote the efflux of H + during nutrient absorption , thereby reducing stress associated with alkaline rhizosphere soils. However, the regulatory mechanisms governing expression of blueberry VcHAs genes are unknown. We isolated promoter fragments upstream of the translational start of nine VcHA genes from Vaccinium spp. Based on the strength of transient promoter::luc expression in tobacco leaves, VcHA11.1- prom was selected for further analyses of cis -acting elements and transcription factors (TFs). In silico and in vitro (yeast one-hybrid - Y1H) studies with a 5-prime deletion VcHA11.1- prom variant (B) were used to identify and verify binding of two blueberry TFs, namely VcDof2.1 and VcbHLH104. Ensuing transient Luc assays in transgenic tobacco leaves revealed that VcbHLH104 upregulated and VcDof2.1 downregulated expression from VcHA11.1 -B-prom. qRT-PCR analysis of RNA isolated from WT blueberry roots confirmed that plants propagated at pH 5.0 resulted in high VcDof2.1 but low VcHA11.1 transcripts. VcbHLH104 transcript levels significantly increased (ca. 242.0%) and paralleled those of VcHA11.1 when plants were cultivated at pH 7.0. Transgenic Arabidopsis seedlings overexpressing VcbHLH104 demonstrated improved H + efflux and alleviated stress at pH ≥ 7.0 with no distinguishable plant etiolation. Conversely, transgenic plants expressing VcDof2.1 displayed weak H + release, poor growth, leaf sparsity and chlorosis at pH ≥ 7.0. We conclude that expression of VcHA11.1 is pH dependent and that promoter transcription is counter regulated by VcDof2.1 and VcbHLH104 at pH ≤ 5.0 and pH ≥ 7.0, respectively. • Nine VcHA gene promoters from Vaccinium spp. isolated and characterized. • First reported isolation of TFs which regulate VcHAs promoters. • VcbHLH104 TF positively activated expression from VcHA11.1 promoter. • VcDof2.1 TF down regulated expression from the VcHA11.1 promoter. • Transgenic Arabidopsis overexpressing VcbHLH104 improved H + efflux and alleviated pH stress.

Phyllopertha horticola Linné - Pest in blueberry plantations in the Mărişel area (Cluj County)

&#x0D; Phyllopertha horticola Linné (Coleoptera: Scarabaeidae) is one of the most common phytophagous beetles in Central Europe. In 2020 the blueberry growers from the Mărişel area reported the presence of a new beetle that attacked the fruit’s flowers and leaves. The species was identified at the University of Agricultural Sciences and Veterinary Medicine in Cluj-Napoca as the garden chafer. In the following year, the plants attacked by the garden beetle were monitored in the blueberry plantation in the Mărişel area. For monitoring the garden chafer, three rows of land were randomly selected in each plot with intervals of 20 plants per row. Each plant was analyzed individually and the number of adult beetles reported on the plant was noted. The observations were made between June and July 2021. In the Elliot variety, the share of plants reported with adults of Phyllopertha horticola Linné was between 50% and 60%, the average being 55%. Regarding the maximum number of adults/plant, it was between 6 specimens (raw 1) and 9 adults/plant (raw 2). In the Bluecrop variety, the share of plants with adults of the monitored species was between 10% and 45%, with an average per variety of 25%.&#x0D;

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.

Testing of a new high voltage electrical discharge generator prototype at high frequencies to assist anthocyanin extraction from blueberries

Traditional extraction methods are based on high-temperature maceration with organic solvents, which are dangerous for human health. A viable alternative to overcome the issues associated with conventional extraction is to increase cell tissue permeability by applying high voltage electrical discharge (HVED) treatments. The objective of this work was to validate the electroporation of blueberry plant cells using a new HVED generator prototype at a high frequency, investigate the effect, intensity, and duration of the applied voltage, and recover anthocyanins from its electroporated cells. The electroporation level of the HVED-treated blueberries was measured qualitatively by transmission electron microscopy (TEM) analysis. Meanwhile, it was quantitatively measured by the cell permeabilization index (Zp) and anthocyanin extraction level. Results of the micrographs (TEM) showed electroporation in all treatments in which Zp was 0.24 when applying a 2 kV treatment for 2 s, whereas a 3-fold increase in tissue damage was revealed with the most powerful treatment (10 kV voltage, 30 s). In addition, anthocyanin values ranged from 83.09 ± 1.20 (control) to 136.82 ± 0.84 (HVED), which was 64.66% higher. The HVED treatment can increase mass transfer rates during conventional extraction processes. It should be noted that the validated prototype required a low specific energy requirement (31–204 kJ/kg) for proper tissue electropermeabilization. In conclusion, we demonstrated the capability of the developed HVED prototype to boost mass transfer phenomena and thus potentially increase its adaptability to assist dissimilar industrial processes or waste (e.g., peels and seeds) such as freeze-drying operations.

Microbiota Modulation in Blueberry Rhizosphere by Biocontrol Bacteria

Microbial interactions in agricultural soils can play important roles in the control of soil-borne phytopathogenic diseases. Yields from blueberry plantations from southern Spain have been impacted by the pathogenic fungus, Macrophomina phaseolina. The use of chemical fungicides has been the common method for preventing fungal infections, but due to their high environmental impact, legislation is increasingly restricting its use. Biocontrol alternatives based on the use of microorganisms is becoming increasingly important. Using the metabarcoding technique, fungi and bacteria were characterized (via 16S and ITS regions, respectively) from rhizosphere soils of healthy and dead blueberry plants infected by M. phaseolina, and which had undergone three different treatments: two biocontrol strategies—one of them a mix of Pseudomonas aeruginosa and Bacillus velezensis and the other one with Bacillus amyloliquefaciens—and a third treatment consisting of the application of a nutrient solution. The treatments produced changes in the bacterial microbiota and, to a lesser extent, in the fungi. The abundance of Fusarium was correlated with dead plants, likely favoring the infection by M. phaseolina. The presence of other microorganisms in the soil, such as the fungi Archaeorhizomyces or the bacteria Actinospica, were correlated with healthy plants and could promote their survival. The different genera detected between dead and healthy plants opens the possibility of studying new targets that can act against infection and identify potential microorganisms that can be used in biocontrol strategies.

Validation of Reference Genes in a Population of Blueberry (Vaccinium corymbosum) Plants Regenerated in Colchicine.

For the first time we report the validation of reference genes in plants from a population of blueberry (Vaccinium corymbosum) clones cultured in vitro on a colchicine-supplemented medium. Nodal segment explants of the cultivar Duke were regenerated by organogenesis under different periods of colchicine 1 mg/L exposure (1, 2, 3, 5, 30 days). The clones selected for the study showed variability for phenotypic traits after 2 years of adaptation to field conditions, compared to plants of the donor genotype that were regenerated on a medium without colchicine. Vaccinium myrtillus (GAPDH) and Vaccinium macrocarpon (ATP1, NADH, RPOB and COX2) were used as reference genomes for primer design. The results show that colchicine treatments can cause genomic changes in blueberry plants. At the molecular level, exposure of plants to colchicine in early periods could promote an increase in gene expression of specific genes such as ATP1, COX2, GAPDH, MATK, NADH and RPOB. However, prolonged exposure (30 days) could decrease gene expression of the genes studied. For qPCR assays, the primers designed for ATP1, COX2, GAPDH and MATK genes showed high efficiency. In addition, the GAPDH, ATP1, NADH and COX2 genes showed high stability and could be recommended as potential reference genes for gene expression assays in Vaccinium.

Application of anthocyanins as indicators for alkalimetric titration

Along with synthetic substances, various naturally-occurring pigments can response to pH variations in solutions by changing their colour. Such substances include, for example, anthocyanins. In this study, the possibility of applying a set of anthocyanins obtained from berry extracts as a potential acid-base indicator. This indicator can be a good alternative to the widely-used phenolphthalein test. Aqueous and alcoholic extracts derived from the fruit of ashberry, sea-buckthorn, lingonberry, blueberry, currant, blackberry, cranberry, rose hip, cherry and hawthorn plants were studied. The presence of anthocyanins in the test samples was confirmed by chemical and physicochemical methods of analysis, including qualitative tests, ascending thin-layer chromatography and direct spectrophotometry. Quantification of anthocyanins was carried out by pH-differential spectrophotometry. Compared to alcoholic extracts, aqueous berry extracts were found to contain anthocyanins in far lesser amounts. In order to compare the pH indicator potential of phenolphthalein and the studied set of anthocyanins, the content of ascorbic acid in the test samples was assessed by direct alkalimetry. A control experiment was performed using a 5% ascorbic acid solution for injection. The pH value of aqueous and alcoholic solutions of all berry extracts was determined by an instrumental procedure. The pH of the extracts ranged from 2.95 to 5.04. The content of the total amount of anthocyanins in aqueous and alcoholic extracts of blackberries, cranberries, black currants, blueberries and lingonberries in terms of cyanidin-3-glucoside was determined both quantitatively and qualitatively. A good agreement was achieved between the results of alkalimetric titration performed using phenolphthalein and the set of anthocyanins extracted from blackcurrant berries with 95% ethanol.

Enhancing soil fertility and lowbush blueberry (Vaccinium angustifolium) growth using bio-organic fertilizer

Acid soils contain high concentrations of aluminum and ferrous ions, which limit crop growth and the available plant nutrients. The current work was to determine the effects of bio-organic fertilizer (BOF) application on soil quality and the growth of blueberry cultivated in acid soil. A completely randomized block design was arranged, with four doses of BOF (0, 2, 4, and 6 t ha–1 yr–1). Each treatment was carried out with four replicates. In the present work, soil quality properties such as pH, soil organic matter, available phosphorus, total nitrogen, aluminum (Al3+), and iron (Fe2+) were measured. Additionally, the influence of organic fertilizer on the growth of blueberry (plant height, number of shoots, and leaves) was also investigated. The results indicated that both the rates of BOF (4 and 6 t ha−1 yr–1) significantly improved soil organic matter and available phosphorus. Also, BOF application greatly decreased the soil concentrations of Al3+ and Fe2+ compared to the control treatment. Similarly, 12 months after planting, the number of shoots and leaves was improved in the pots with BOF compared to that without BOF addition. From the results of this study, we recommend using BOF as the best measure for enhancing soil health and blueberry growth.

Analysis of Blueberry Plant Rhizosphere Bacterial Diversity and Selection of Plant Growth Promoting Rhizobacteria.

Microbial metabolites in rhizosphere soil are important to plant growth. In this study, microbial diversity in blueberry plant rhizosphere soil was characterized using high-throughput amplicon sequencing technology. There were 11 bacterial phyla and three fungal phyla dominating in the soil. In addition, inorganic-phosphate-solubilizing bacteria (iPSB) in the rhizosphere soil were isolated and evaluated by molybdenum-antimony anti-coloration method. Their silicate solubilizing, auxin production, and nitrogen fixation capabilities were also determined. Eighteen iPSB in the rhizosphere soil strains were isolated and identified as Buttiauxella, Paraburkholderia and Pseudomonas. The higher phosphorus-solubilizing capacity and auxin production in blueberry rhizosphere belonged to genus Buttiauxella sp. The strains belong to genus Paraburkholderia had the same function of dissolving both phosphorus and producing auxin, as well as silicate and nitrogen fixation. The blueberry seeds incubated with the strains had higher germination rates. The results of this study could be helpful in developing the plant growth-promoting rhizobacteria (PGPR) method for enhancing soil nutrients to blueberry plant.

Substrate composition affects growth and physiological parameters of blueberry

There is currently a growing interest in soilless substrates for blueberry cultivation. Identifying optimal substrate for the growth and development of the crop, and understanding the physiological response of blueberries is not only essential to determine the appropriate growing conditions, but also to improve the quality of the fruit. In this study, we evaluated the development and physiological response, and quality of blueberry plant fruits grown on two types of substrate. For this, the “Legacy” variety blueberry plants (Vaccinium. corymbosum, L) were grown in substrate composed of coconut fiber and peat (3:1) (substrate 1) and in substrate only composed of coconut fiber (substrate 2). The plants were kept in a greenhouse with controlled humidity and temperature conditions, and were drip-irrigated with modified Steiner solution. The blueberry plants grown in substrate 2, had a higher growth and yield compared to substrate 1. The analysis of nutrients in the substrate showed a higher concentration of nutrients in substrate 1, but in a post-transplant percolate analysis, substrate 2 was found to have a higher nutrient retention. Also, the stomatal density and the stomatal conductance show significant and differences and opposite response with the treatments, finding the highest number of stomata per mm2 in the plants grown with substrate 2, and a higher stomatal conductance with substrate 1. The plants with substrate 2 showed a better fruiting potential and reached a larger fruit diameter. The results indicate a higher suitability of substrate 2 for growing blueberry, but not only due to the values obtained, but for the potential better response against any environmental change that could alter water relations.

Long-term cultivation drives dynamic changes in the rhizosphere microbial community of blueberry.

Rhizosphere microbial communities profoundly affect plant health, productivity, and responses to environmental stress. Thus, it is of great significance to comprehensively understand the response of root-associated microbes to planting years and the complex interactions between plants and rhizosphere microbes under long-term cultivation. Therefore, four rabbiteye blueberries (Vaccinium ashei Reade) plantations established in 1988, 2004, 2013, and 2017 were selected to obtain the dynamic changes and assembly mechanisms of rhizosphere microbial communities with the increase in planting age. Rhizosphere bacterial and fungal community composition and diversity were determined using a high-throughput sequencing method. The results showed that the diversity and structure of bacterial and fungal communities in the rhizosphere of blueberries differed significantly among planting ages. A total of 926 operational taxonomic units (OTUs) in the bacterial community and 219 OTUs in the fungal community were identified as the core rhizosphere microbiome of blueberry. Linear discriminant analysis effect size (LEfSe) analysis revealed 36 and 56 distinct bacterial and fungal biomarkers, respectively. Topological features of co-occurrence network analysis showed greater complexity and more intense interactions in bacterial communities than in fungal communities. Soil pH is the main driver for shaping bacterial community structure, while available potassium is the main driver for shaping fungal community structure. In addition, the VPA results showed that edaphic factors and blueberry planting age contributed more to fungal community variations than bacterial community. Notably, ericoid mycorrhizal fungi were observed in cultivated blueberry varieties, with a marked increase in relative abundance with planting age, which may positively contribute to nutrient uptake and coping with environmental stress. Taken together, our study provides a basis for manipulating rhizosphere microbial communities to improve the sustainability of agricultural production during long-term cultivation.

Southern highbush blueberry responses to humic acid application in soilless substrates

Humic acids are a biostimulant that has captured the interest of blueberry growers, but information about humic acid use in blueberry is scarce. Blueberry plants suffer water deficit stress during transplant and photosynthetic limitations during fruit development. We hypothesized that humic acid applications improve transplant success and increase fruit yield and quality in southern highbush blueberry (SHB, Vaccinium corymbosum interspecific hybrids) grown in soilless substrates. We tested these hypotheses in two greenhouse experiments. First, we grew ‘Sweetcrisp’ SHB in rhizoboxes. Humic acids were applied via drench at concentrations of 0 mL⋅L−1, 7 mL⋅L−1, 13 mL⋅L−1, and 24 mL⋅L−1 for 10 weeks. Humic acid application increased substrate respiration rates, pH, and electrical conductivity, but they did not increase root growth or improved transplant success. In a separate experiment, one year-old plants of ‘Avanti’, FL 09-311, and FL 06-19 SHB plants in 1.7 L pots were treated with 0 mL⋅L−1, 13 mL⋅L−1, and 24 mL⋅L−1 humic acids during the fruit development period. Humic acid application did not increase yields and occasionally reduced fruit quality. While plant responses were genotype specific, these results suggest that humic acid applications are not beneficial during the transplant or fruit development periods in substrate-grown blueberry.

Improvement of Ex Vitro Growing Completion of Highbush Blueberry (Vaccinium corymbosum L.) in Containers

Highbush blueberry (Vaccinium corymbosum L.), originally a forest plant, is currently in need of improvement of clonal micropropagation technologies. It is known that the large percentage of propagated plants can be lost or damaged, not only at the stage of acclimatization to non-sterile conditions, but also during the growing completion stage. In fact, successful ex vitro regeneration of such plants is determined by their ability to produce new shoots that can adapt to new cultivation conditions. The lighting and ratio of nutrients under ex vitro conditions play an important role in the development of the plants’ photosynthetic capacity. The research revealed that LED grow lighting has a positive effect on the development of ex vitro plants of highbush blueberry (Vaccinium corymbosum L.) cv. Brigitta Blue, only at the initial stages of growing in 0.5-L containers. The results obtained have improved our understanding of lighting and mineral fertilizer’s impact on the development of ex vitro plants of the highbush blueberry (Vaccinium corymbosum L.) cv. Brigitta Blue in greenhouse conditions. This can be useful for providing blueberry planting stock and commercial use for large scale production.