Vaccinium Corymbosum Research Articles

Weather-based Scheduling and Pulse Drip Irrigation Increase Growth and Production of Northern Highbush Blueberry

Northern highbush blueberry (Vaccinium corymbosum L.) often requires frequent irrigation for commercial production, but irrigation is becoming increasingly challenging for many growers because of warmer and drier weather conditions, increased water regulations, and other water-use limitations. The purpose of this study was to develop improved methods of irrigation to prepare the industry more effectively against future water uncertainties. Treatments were applied for 2 years (2021 and 2022) and included a combination of weather-based or fixed irrigation schedules using continuous or pulse irrigation in a commercial field of ‘Draper’ blueberry in eastern Washington, USA. The soil at the site was a silt loam, and irrigation was applied using two laterals of drip tubing per row. Plants on a fixed schedule were irrigated for 12 to 13 hours per application (set by the grower), whereas those on a weather-based schedule were irrigated according to daily estimates of crop evapotranspiration (downloaded from an automated weather station). In both cases, irrigation was applied every 2 to 4 days as a single, continuous application or in 30- to 50-minute pulses every 2 hours (up to nine times per day) with the same amount of water as the continuous treatment. During the first year of the study, weather-based scheduling maintained greater stem water potentials in the plants and, on average, increased yield by 3.4 t⋅ha–1, berry weight by 0.14 g/berry, berry diameter by 0.4 mm, and fruit bud set by 4.3% when compared with fixed scheduling. Likewise, pulse irrigation maintained greater stem water potentials and, on average, increased berry weight and diameter by 0.10 g and 0.4 mm, respectively, fruit bud set by 3.3%, and canopy cover by 2.4% relative to continuous irrigation. Yield and canopy cover were unaffected by any treatment in the second year, which was likely a result of uncharacteristically cool, wet weather in the spring. However, weather-based scheduling continued to maintain greater stem water potentials and, when combined with pulse irrigation, increased berry weight and diameter by 3.7 g and 1.0 mm, respectively, relative to continuous irrigation on a fixed schedule. Pulse drip irrigation also increased fruit bud set by 5.1% during the second year. These results demonstrate the potential benefits of using weather-based scheduling and pulse drip in northern highbush blueberry, especially when the plants are grown on light-textured soils in hot, dry climates.

Applying Boron by Fertigation or as a Foliar Fertilizer Is More Effective than Soil Applications in Northern Highbush Blueberry

Boron (B) is often deficient in many fruit crops, including blueberry (Vaccinium sp.). The objective of the present study was to evaluate different methods for applying B fertilizers to two commercial cultivars of northern highbush blueberry (V. corymbosum Earliblue and Aurora) in western Oregon, USA. Treatments included soil application of sodium tetraborate in early April (before bloom), foliar application of boric acid in late April (during bloom or petal fall), weekly fertigation with boric acid from April through July, and a control with no B. The plants were irrigated by drip, and the fertilizers were applied for two consecutive seasons at a total rate of 1.5 kg·ha−1 B per year. Each method of fertilizer application increased the concentration of B in the soil solution relative to the control, but fertigation was the only treatment that increased extractable soil B to the recommended level of 0.5 to 1.0 mg·kg−1 B. In terms of plant nutrition, foliar application of B was the most effective method for increasing the concentration of B in the leaves, roots, and fruit, followed by fertigation. Soil application of B, on the other hand, was relatively ineffective and, after 2 years, only increased the concentration of B in the leaves of ‘Earliblue’. Although leaf B levels were initially deficient at the site (<30 ppm B), none of the B application methods had any effect on yield, berry weight, fruit firmness, or titratable acidity of the fruit in either cultivar. However, foliar applied B resulted in higher concentrations of soluble solids in the fruit than no B or soil applied B in ‘Earliblue’, whereas B fertigation resulted in higher concentrations of soluble solids than soil applied B in ‘Aurora’. On the basis of these results, applying B by fertigation or as a foliar spray is recommended over the use of soil applications of B fertilizer in northern highbush blueberry.

Molecular mechanism of abscisic acid signaling response factor VcbZIP55 to promote anthocyanin biosynthesis in blueberry (Vaccinium corymbosum)

A high content of anthocyanin in blueberry (Vaccinium corymbosum) is an important indicator to evaluate fruit quality. Abscisic acid (ABA) can promote anthocyanin biosynthesis, but since the molecular mechanism is unclear, clarifying the mechanism will improve for blueberry breeding and cultivation regulation. VcbZIP55 regulating anthocyanin synthesis in blueberry were screened and mined using the published Isoform-sequencing, RNA-Seq and qRT-PCR at different fruit developmental stages. Blueberry genetic transformation and transgenic experiments confirmed that VcbZIP55 could promote anthocyanin biosynthesis in blueberry adventitious buds, tobacco leaves, blueberry leaves and blueberry fruit. VcbZIP55 responded to ABA signals and its expression was upregulated in blueberry fruit. In addition, using VcbZIP55 for Yeast one hybrid assay (Y1H) and transient expression in tobacco leaves demonstrated an interaction between VcbZIP55 and a G-Box motif on the VcMYB1 promoter to activate the expression of VcMYB1. This study will lay the theoretical foundation for the molecular mechanisms of phytohormone regulation responsible for anthocyanin synthesis and provide theoretical support for blueberry quality improvement.

Preparing a Southern Highbush Blueberry Field for Machine Harvesting

Blueberries are grown commercially in Florida for the early-season fresh fruit market. The majority of Florida’s blueberry crop is currently harvested by hand to ensure high quality standards for fresh fruit production. However, hand harvesting is the single greatest annual production cost for Florida blueberry growers, and mechanization of berry harvests could greatly reduce production costs. This is particularly important when considering the volume of fruit imported into the United States from countries where labor rates are significantly lower. Also, at times the availability of harvest labor when needed may be an issue for Florida growers; mechanization could help address that issue. This publication provides information for commercial blueberry growers interested in adopting machine harvesting.

Gradual pollen presentation in Vaccinium corymbosum 'Bluecrop': an adaptive mechanism to improve pollination efficiency and outcrossing.

Gradual pollen presentation is a plant reproductive mechanism to improve pollination efficiency and accuracy and promote outcrossing. Vaccinium corymbosum 'Bluecrop' has a typical gradual pollen presentation mechanism. 'Bluecrop' exhibits an inverted bell-shaped flower with a white coloration. By investigating the flower syndrome, pollination characteristics, pollination efficiency, and breeding system of 'Bluecrop', this study aims to explore the adaptive significance of these traits. The results showed 'Bluecrop' released pollen gradually through anther poricidal dehiscence. Among different pollinators, Apis mellifera and Bombus can pollinate effectively, and the mechanism of gradual pollen presentation significantly improved the efficiency of pollen transfer. This characteristic limits the amount of pollen removed by the pollinators and prolongs pollen presentation, thus attracting more pollinators and thereby increasing male fitness. The nectar secretion of 'Bluecrop' is gradual, with a large nectar production and a long phase of nectar secretion, enhance visitation frequencies and the chances of successful pollination. At the same time, campanulate corolla can protect pollen as well as nectar from waste due to environmental factors and other effects. The breeding system of 'Bluecrop' relies mainly on outcrossing because of its low affinity for self-fertilization and good interaction with pollinating insects. Thus, the special floral syndrome and the mechanism of secondary pollen presentation are significant in improving pollination efficiency and promoting the reproductive success of 'Bluecrop' by outcrossing. It can provide a certain theoretical basis for the future propagation breeding of 'Bluecrop'.

Do aluminum (Al)-hyperaccumulator and phosphorus (P)-solubilising species assist neighbouring plants sensitive to Al toxicity and P deficiency?

We aimed to evaluate the facilitation effects of an aluminum (Al) hyperaccumulator species bearing cluster roots, Gevuina avellana, on the seedling growth and performance of an Al-intolerant and phosphorus (P)-deficient-sensitive plant, Vaccinium corymbosum. For this, seedlings of G. avellana and V. corymbosum were grown alone or together as follows: i) two G. avellana seedlings, ii) one G. avellana + one V. corymbosum and iii) two V. corymbosum, in soil supplemented with Al (as Al2(SO4)3) and in the control (without Al supplementation). We determined relative growth rate (RGR), photosynthetic rate, chlorophyll concentration, lipid peroxidation and Al and nutrient concentration [Nitrogen (N), P, potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), and sulfur (S)] in leaves and roots of both species. The results showed that, in general, G. avellana did not assist V. corymbosum to enhance its RGR nor reduce its Al uptake. However, G. avellana assisted V. corymbosum in enhanced N acquisition and, consequently, to increase its chlorophyll concentration and photosynthetic rate. Besides, V. corymbosum had lower lipid peroxidation in leaves when grown in the soil with high Al supplementation in association with G. avellana. Our results suggest a facilitating effect of G. avellana to V. corymbosum when grown in soils with high Al concentration, by enhancing chlorophyll concentrations and photosynthetic rate, and decreasing the oxidative damage to lipids.

Comparative transcriptome and functional analyses provide insights into the key factors regulating shoot regeneration in highbush blueberry

Comparative transcriptome and functional analyses provide insights into the key factors regulating shoot regeneration in highbush blueberry

The influence of soil carbonates on highbush blueberry plants in the conditions of the Kabardino-Balkarian Republic

The article studies the influence of soil carbonates on the plants, the yield and the quality of highbush blueberries in the conditions of the Kabardino-Balkarian Republic. The carbonates in the soil solution lead to an increase in soil pH, which negatively affects its development. High bush blueberries have special soil requirements for normal growth and development. It is necessary to provide the plant with a breathable substrate with an optimal acidity level of up to 5.5 units. Acidic conditions are necessary due to the unique structure of the root system: highbush blueberries are completely devoid of root hairs; their function is performed by a colony of fungi, which constitutes mycorrhiza in symbiosis with the plant. Mycorrhiza functions only in acidic conditions. The research provides average data for the period of 2021-2023. Blueberry plants grown in carbonate areas are characterized by weak growth, few shoots to form, low foliage and chlorosis due to reduced food availability. The size of the berries and their taste play a huge role for producers. The measurement of this parameter showed that in the main part of the field, under the best growing conditions, the average diameter of the berries is 17 mm, which is 23.5% more than in carbonate areas, where the diameter is, on average, 13 mm. The accumulation of sugar in berries with increased soil carbonate decreases by2.3%, which significantly affects their taste. As a result of the research, a negative effect of soil carbonates on the development of blueberry plants has been noted, as well as yield reduction by 79.5%. The negative effect of increasing pH to neutral or, especially, slightly alkaline on plant development is associated with deterioration of nutrition and poor development of the root system.

Effect of Elicitor Treatments on Quality Attributes in Blueberry: Implications of Cultivar and Environmental Conditions.

Elicitors of plant defence responses can trigger defence mechanisms that are able to protect plant tissues from biotic or abiotic stresses. Since one defence response involves the activation of secondary metabolites' biosynthesis, the purpose of this study was to evaluate the effect of chitosan and melatonin pre-harvest treatments on the quality and the nutritional parameters of the fruits of blueberry (Vaccinium corymbosum L.). Across the two years of experiment, three different cultivars (cv.s. 'Cosmopolitan', 'Hortblue Poppins' and 'Legacy') were treated with 1% chitosan or 100 µM melatonin every two weeks during the ripening season and ripe fruits were progressively harvested and analysed. The treatment with both elicitors had only slight effects on dry matter, soluble solids content, titratable acidity and pH, with a cultivar-dependent response. On the other hand, elicitors significantly affected the levels of phenylpropanoid and antioxidant compounds in all cvs. in both years, with a higher accumulation of total anthocyanins and phenolics and the enhancement of the antioxidant capacity, with positive effects on the nutraceutical quality of fruits. The anthocyanin profile in terms of both absolute concentrations and the relative proportion of single anthocyanins was affected by both harvest year and cv., highlighting the role of the genetic background in the plant response to environmental conditions (with particular reference to summer heat stress) and to elicitor treatments.

Host range of Phytophthora spp. from berry crops in Huelva, Spain.

Crop declines have been observed in raspberry and blueberry farms in the southwest region of Spain, which is the most important berry-producing area in the country. This study aimed to identify and characterize the pathogens associated with these diseases using molecular and morphological methods. Additionally, pathogenicity tests were performed on different raspberry, blueberry, and strawberry cultivars to determine possible susceptible hosts in the area. An isolate of P. cactorum was obtained from a symptomatic strawberry plant, an isolate of P. cinnamomi was obtained from a symptomatic blueberry plant, and isolates identified as P. rosacearum, P. rubi and a previously unknow speciesrecently named as P. sp. balkanensis were recovered from symptomatic raspberry plants. Results from the pathogenicity tests reported, for the first time, P. rubi causing root rot and wilting complex (RRWC) in Spanish raspberry crops. Additionally, P. cinnamomi was found to affect highbush blueberry production in Spain. Thus, this study provides valuable insights into the identification and characterization of Phytophthora spp. associated with the decline of blueberry and raspberry crops in Huelva. It also provides essential recommendations regarding the potential risks associated with the use of other types of berries as rotational crops and emphasizes the necessity for effective management strategies to mitigate crop losses. This is particularly critical given the limited soil disinfection alternatives available in Spain.

A public mid-density genotyping platform for cultivated blueberry (Vaccinium spp.)

Small public breeding programmes have many barriers to adopting technology, particularly creating and using genetic marker panels for genomic-based decisions in selection. Here we report the creation of a DArTag panel of 3,000 loci distributed across the tetraploid genome of blueberry (Vaccinium corymbosum) for use in molecular breeding and genomic prediction. The creation of this marker panel brings cost-effective and rapid genotyping capabilities to public and private breeding programmes. The open access provided by this platform will allow genetic data sets generated on the marker panel to be compared and joined across projects, institutions and countries. This genotyping resource has the power to make routine genotyping a reality for any breeder of blueberry.

Honey bee stressor networks are complex and dependent on crop and region

Honey bees play a major role in crop pollination but have experienced declining health throughout most of the globe. Despite decades of research on key honey bee stressors (e.g., parasitic Varroa destructor mites and viruses), researchers cannot fully explain or predict colony mortality, potentially because it is caused by exposure to multiple interacting stressors in the field. Understanding which honey bee stressors co-occur and have the potential to interact is therefore of profound importance. Here, we used the emerging field of systems theory to characterize the stressor networks found in honey bee colonies after they were placed in fields containing economically valuable crops across Canada. Honey bee stressor networks were often highly complex, with hundreds of potential interactions between stressors. Their placement in crops for the pollination season generally exposed colonies to more complex stressor networks, with an average of 23 stressors and 307 interactions. We discovered that the most influential stressors in a network-those that substantively impacted network architecture-are not currently addressed by beekeepers. Finally, the stressor networks showed substantial divergence among crop systems from different regions, which is consistent with the knowledge that some crops (e.g., highbush blueberry) are traditionally riskier to honey bees than others. Our approach sheds light on the stressor networks that honey bees encounter in the field and underscores the importance of considering interactions among stressors. Clearly, addressing and managing these issues will require solutions that are tailored to specific crops and regions and their associated stressor networks.

Investigation of salinity tolerance to different cultivars of highbush blueberry (Vaccinium corymbosum L.) grown in vitro

Salinity is one of the most critical abiotic stresses affecting various physiological, biochemical, and molecular functions of plants. This study aimed to assess the effects of different salt concentrations on in vitro blueberry shoots (‘Bluecrop’, ‘Blueray’, ‘Brigitta Blue’, ‘Duke’, ‘Goldtraube’, ‘Hortblue Petite’, and ‘Patriot’ cultivars) and to understand the mechanisms employed by this species under saline conditions. The Woody Plant Medium (WPM) proliferation medium was supplemented with 10, 50, 100, and 150 mM NaCl to induce salt stress. After ten weeks of in vitro culture under salinity stress, various parameters were evaluated, including the number of shoots obtained/explant, shoot length, fresh weight, dry weight, water content, stress tolerance index (STI), and McKinney index (MKI). Additionally, the behaviour of blueberry cultivars under salt stress was analyzed using electron paramagnetic resonance spectroscopy (EPR). Compared to the control (culture medium without NaCl), all treatments with NaCl reduced shoot length and the number of shoots obtained/explant in all studied blueberry cultivars. ‘Brigitta Blue’ reported the shortest shoots (0.04 ± 0.02 cm) at a concentration of 150 mM NaCl, followed by ‘Blueray’ with 0.05 ± 0.03 cm. Also, the lowest number of shoots/explant was recorded for both cultivars under 150 mM NaCl, namely 0.12 ± 0.07 shoots/explant (‘Brigitta Blue’) and 0.11 ± 0.04 shoots/explant (‘Blueray’). Salt tolerance, as expressed by ITS and MKI, confirmed that ‘Goldtraube’ exhibited higher salt tolerance, with the highest ITS values and the lowest MKI values. Further validation presented ‘Goldtraube’ as the most unresolved spectra of the Mn (II) hyperfine structure under all salt concentrations, therefore ‘Goldtraube’ was the most tolerant to saline stress.

Management of the Blueberry Gall Midge in Florida’s Southern Highbush Blueberries

The blueberry gall midge (BGM) is one of the most important pests of southern highbush blueberries in Florida. Monitoring for BGM using clear sticky traps or bucket traps should begin as early as November. Chemical control should be applied right before bud break and then ten days after bud break, or when at least two BGM are found on traps. Other management practices include the use of younger mulch, using potentially resistant cultivars, and chemical control such as Movento with Induce and Apta in rotation to avoid resistance development. Applications should also be timed with larval and adult emergence for optimal insecticide efficacy. 

Transcriptome-Based Identification of Candidate Flowering-Associated Genes of Blueberry in a Plant Factory with Artificial Lighting (PFAL) under Short-Day-Length Conditions.

In blueberry (Vaccinium corymbosum L.), a perennial shrub, flower bud initiation is mediated by a short-day (SD) photoperiod and buds bloom once the chilling requirement is satisfied. A plant factory with artificial lighting (PFAL) is a planting system that can provide a stable and highly efficient growing environment for blueberry production. However, the characteristics of bud differentiation of blueberry plants inside PFAL systems are poorly understood. To better understand flower bud initiation and the flowering mechanism of blueberry in PFAL systems, the anatomical structure of apical buds under SD conditions in a PFAL system was observed using the southern highbush cultivar 'Misty' and a transcriptomic analysis was performed to identify the candidate flowering genes. The results indicated that the apical bud of 'Misty' differentiated gradually along with SD time course and swelled obviously when chilling was introduced. A total of 39.28 Gb clean data were generated, and about 20.31-24.11 Mb high-quality clean reads were assembled, yielding a total of 17370 differentially expressed genes (DEGs), of which 9637 were up-regulated and 7733 were down-regulated. Based on the functional annotation, 26 DEGs were identified including 20 flowering-related and 6 low-temperature DEGs, out of which the expressive level of four flowering-related DEGs (VcFT2, VcFPA, VcFMADS1, and VcCOP1) and two low-temperature-induced DEGs (VcTIL-1 and VcLTI 65-like) were confirmed by qRT-PCR with a good consistency with the pattern of transcriptome. Functional analysis indicated that VcFT2 was highly conserved with nuclear and cytoplasmic subcellular localization and was expressed mainly in blueberry leaf tissue. In Arabidopsis, ectopic overexpression of VcFT2 results in an early flowering phenotype, indicating that VcFT2 is a vital regulator of the SD-mediated flowering pathway in blueberry. These results contribute to the investigation of photoperiod-mediated flowering mechanisms of blueberry in PFAL systems.

Methyl Jasmonate Improves Antioxidants, Protecting Photosynthetic Apparatus in Blueberry Plants under Water Deficit

The plant water status is crucial for growth and production, but the current climate change scenario makes it challenging to match the water plant demand. Blueberries are an economically important crop and play an acknowledged role in human health due to their antioxidant compounds. This research aimed to determine whether the exogenous application of methyl jasmonate (MeJA) improves the antioxidant defense mechanisms for protecting the photosynthetic performance in the blueberry plant cultivar ‘Brigitta’ under the stress condition of a water deficit (WD). A greenhouse experiment was carried out under a 16-h light period, at 20 °C, and 60–80% relative humidity for two weeks before the application of MeJA to the blueberry plants (Vaccinium corymbosum, cultivar ‘Brigitta’). The following treatments were maintained for 7-days: (i) 80% field capacity (NoWD), (ii) 80% field capacity plus MeJA application (NoWD + MeJA), (iii) 20% field capacity (WD), and (iv) 20% field capacity plus MeJA application (WD + MeJA). The MeJA was sprayed as an aqueous solution of 10 µM MeJA over the plant’s foliar system. At the end of the assay, the blueberry leaves were analyzed for their relative water content, specific leaf area, lipid peroxidation, total antioxidant activity, total phenols, total anthocyanins, anthocyanidin compounds, and photosynthetic performance. The ‘Brigitta’ cultivar showed a significant decrease in the oxidative stress at leaf levels, with an increase in antioxidant activity, phenolic compounds, total anthocyanins, delphinidin, petunidin, antheraxanthin, zeaxanthin, and an improvement in photosynthetic performance parameters. The ‘Brigitta’ blueberry cultivar was shown to be susceptible to WD, which mainly decreased photosynthesis. However, the application of MeJA to the leaves induced metabolic changes through an increase of the antioxidant strategy within the plant to counteract the negative effects of WD and protect the photosynthetic apparatus, which allowed the ‘Brigitta’ cultivar to withstand the period of a WD.

Survival of Listeria Strains and Shelf Life Determination of Fresh Blueberries (Vaccinium corymbosum) Treated with Cold Atmospheric Plasma.

Fresh blueberries are delicate, hand-picked, packaged, and refrigerated fruits vulnerable to spoilage and contamination. Cold atmospheric plasma (CAP) is a promising antimicrobial technology; therefore, this study evaluated the CAP treatment effect on acid-tolerant Listeria innocua and Listeria monocytogenes and evaluated changes in the quality of the treated fruit. Samples were spot-inoculated with pH 5.5 and 6.0 acid-adapted Listeria species. Samples were treated with gliding arc CAP for 15, 30, 45, and 60 s and evaluated after 0, 1, 4, 7, and 11 days of storage at 4 °C and 90% humidity for the following quality parameters: total aerobic counts, yeast and molds, texture, color, soluble solids, pH, and titratable acidity. CAP treatments of 30 s and over demonstrated significant reductions in pathogens under both the resistant strain and pH conditions. Sixty-second CAP achieved a 0.54 Log CFU g-1 reduction in L. monocytogenes (pH 5.5) and 0.28 Log CFU g-1 for L. monocytogenes (pH 6.0). Yeast and mold counts on day 0 showed statistically significant reductions after 30, 45, and 60 s CAP with an average 2.34 Log CFU g-1 reduction when compared to non-CAP treated samples. Quality parameters did not show major significant differences among CAP treatments during shelf life. CAP is an effective antimicrobial treatment that does not significantly affect fruit quality.

A Better Fruit Quality of Grafted Blueberry Than Own-Rooted Blueberry Is Linked to Its Anatomy.

To further clarify the impact of different rootstocks in grafted blueberry, fruit quality, mineral contents, and leaf gas exchange were investigated in 'O'Neal' blueberry (Vaccinium corymbosum) grafted onto 'Anna' (V. corymbosum) (AO), 'Sharpblue' (V. corymbosum) (SO), 'Baldwin' (V. virgatum) (BO), 'Plolific' (V. virgatum) (PO), and 'Tifblue' (V. virgatum) (TO) rootstocks and own-rooted 'O'Neal' (NO), and differences in anatomic structures and drought resistance were determined in AO, TO, and NO. The findings revealed that fruit quality in TO and PO was excellent, that of BO and SO was good, and that of AO and NO was medium. 'Tifblue' and 'Plolific' rootstocks significantly increased the levels of leaf phosphorus and net photosynthetic rate of 'O'Neal', accompanied by a synchronous increase in their transpiration rates, stomatal conductance, and intercellular CO2. Additionally, the comprehensive evaluation scores from a principal component analysis based on anatomic structure traits from high to low were in the order TO > AO > NO. The P50 (xylem water potential at 50% loss of hydraulic conductivity) values of these grafted plants descended in the order NO > AO > TO, and the branch hydraulic conductivity of TO and sapwood hydraulic conductivity of TO and AO were significantly lower than those of NO. Thus, TO plants exhibited the strongest drought resistance, followed by AO, and NO, and this trait was related to the effects of different rootstocks on the fruit quality of 'O'Neal' blueberry. These results provided a basis for a deeper understanding of the interaction between rootstocks and scions, as well mechanisms to improve blueberry fruit quality.

Exogenous Abscisic Acid Regulates Anthocyanin Biosynthesis and Gene Expression in Blueberry Leaves

Blueberry (Vaccinium corymbosum) leaves have a positive influence on health because of their phenolic contents, including anthocyanins. Phytohormone abscisic acid (ABA) promotes anthocyanin accumulation, but the underlying mechanisms are unclear in blueberry leaves. In this study, we found that exogenous ABA promotes anthocyanin accumulation in blueberry leaves and we explored the global molecular events involved in these physiological changes by treating in vitro-grown blueberry seedlings with ABA and performing transcriptome deep sequencing (RNA-seq). We identified 6390 differentially expressed genes (DEGs), with 2893 DEGs at 6 h and 4789 at 12 h of ABA treatment compared to the control. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to plant hormone signal transduction and phenylpropanoid and flavonoid biosynthesis were significantly enriched at both stages of the ABA treatment. Analysis of DEGs in plant hormone signal transduction pathways revealed that exogenous ABA affected the expression of genes from other plant hormone signaling pathways, especially brassinosteroid, auxin, and gibberellin signaling. To elucidate the mechanism driving anthocyanin biosynthesis in blueberry in response to ABA treatment, we screened anthocyanin biosynthesis structural genes (ASG) from the phenylpropanoid and flavonoid biosynthetic pathways, MYB transcription factor genes from R2R3-MYB subgroups 5, 6, and 7 and ABRE-binding factor (ABF) genes from the ABA signal transduction pathway. Pearson’s correlation coefficient (r) analysis indicated that the ABFs, MYBs, and structural genes form a network to regulate ABA-induced anthocyanin biosynthesis and MYBA1 is likely to play an important role in this regulatory network. These findings lay the foundation for improving anthocyanin biosynthesis in blueberry leaves.

Looking in the Scaffold 22 Hotspot for Differentially Regulated Genes Genomic Sequence Variation in Romanian Blueberry Cultivars

Since its domestication about a century ago in North America, highbush blueberry (Vaccinium corymbosum L.) has gained appreciation by consumers worldwide, and the demand for new blueberry varieties is increasing. Whole-genome resequencing can help plant breeders to decrease the time needed to create novel varieties by identifying novel genes linked to fruit-quality traits. The present study analyzed the genetic variability of eight V. corymbosum genotypes, seven Romanian varieties (‘Prod’, ‘Vital’, ‘Azur’, ‘Simultan’, ‘Delicia’, ‘Compact’, and ‘Safir’), and the American variety, ‘Bluecrop’. The analysis of the first ~10 Mb from scaffold 22, a hotspot of genomic variation, in the above-mentioned varieties revealed multiple differences in 11 upregulated and 50 downregulated genes involved in fruit growth and development. Of these differentially regulated genes, two upregulated and five downregulated genes were fully covered by at least 1× coverage depth by sequencing. The genes’ sequence analysis confirmed the high genetic variability of the region, with most of the genes presenting numerous SNPs and some InDels, and indicated that an attempted 10× medium-coverage depth of sequencing for V. corymbosum varieties yields useful preliminary data for use in breeding programs.