Rabbiteye Blueberry Cultivars Research Articles

Detection and Characterization of Xylella fastidiosa subsp. fastidiosa in Rabbiteye Blueberry in South Carolina.

Xylella fastidiosa causes bacterial leaf scorch in southern highbush (Vaccinium corymbosum interspecific hybrids) and is also associated with a distinct disease phenotype in rabbiteye blueberry (V. virgatum) cultivars in the southeastern United States. Both X. fastidiosa subsp. fastidiosa and X. fastidiosa subsp. multiplex have been reported to cause problems in southern highbush blueberry, but so far only X. fastidiosa subsp. multiplex has been reported in rabbiteye cultivars in Louisiana. In this study, we report detection of X. fastidiosa in rabbiteye blueberry plants in association with symptoms of foliar reddening and shoot dieback. High throughput sequencing of an X. fastidiosa-positive plant sample and comparative analyses identified the strain in one of these plants as being X. fastidiosa subsp. fastidiosa. We briefly discuss the implications of these findings, which may spur research into blueberry as a potential inoculum source that could enable spread to other susceptible fruit crops in South Carolina.

Five blueberry anthocyanins and their antioxidant, hypoglycemic, and hypolipidemic effects in vitro.

The dual epidemic of obesity and diabetes mellitus is becoming an important worldwide public health issue. "Diabesity" is the term used to describe the combined detrimental health effects of both diabetes mellitus and obesity/overweight. Currently, food-derived bioactive compounds are suggested to alleviate diabesity. Blueberries are rich in bioactive anthocyanins, which are associated with contributing to preventing obesity and diabetes mellitus. However, the accurate active compounds and the underlying mechanism are still unclear. The objective of this study was to investigate the beneficial effects of blueberry anthocyanin on diabesity. In total, five anthocyanins (delphinidin-3-O-galactoside, delphinidin-3-O-glucoside, petunidin-3-O-galactoside, petunidin-3-O-glucoside, and malvidin-3-O-galactoside) were isolated from rabbiteye blueberry (Vaccinium virgatum) cultivar "Garden blue." All these anthocyanins exhibited oxygen radical absorbance capacity (ORAC), scavenging power of ABTS+, and DPPH-free radical and inhibitory activity of α-glucosidase in vitro. Moreover, some compounds improved glucose uptake and attenuated lipid accumulation in high glucose and oleic acid-treated HepG2 cells. All these results suggest that blueberry anthocyanins have potential antioxidant, hypoglycemic, and hypolipidemic effects, which may benefit the treatment of diabesity.

An analysis of hormones and mineral nutrients in fruit from terminal and lateral racemes of two blueberry cultivars

BACKGROUND: In general, fruit that develops from early-opening flowers ripens earlier than fruit from late-opening flowers. However, the opposite has been observed in the rabbiteye blueberry cultivar “Brightwell” (Vaccinium ashei). OBJECTIVE: From the differences of endogenous hormones and mineral nutrition, with attempt to analyze the reasons for fruit from late-opening flowers on lateral racemes of “Brightwell” ripened earlier than fruit from early-opening flowers on terminal racemes. RESULTS: Fruit from late-opening flowers on lateral racemes of “Brightwell” ripened earlier than fruit from early-opening flowers on terminal racemes. This may be associated with the higher levels of giberellin 1, abscisic acid (ABA), salicylic acid, jasmonic acid, phosphorus, iron and boron in the early developmental stages, and the higher ABA level and lower giberellin 9 level in the fruit ripening stages on lateral racemes, compared with on terminal racemes. However, the fruit borne on the terminal racemes of “O’Neal” grew faster than fruit borne on lateral racemes, this may be correlated with the higher IAA, iron, manganese, zinc and boron levels, and the lower ABA level, in the early fruit developmental stages on terminal racemes, compared with on lateral racemes. CONCLUSIONS: The growth and ripening differences in fruit set at the two positions of the two blueberry cultivars may be associated with hormonal and nutritional control during fruit development.

Bacterial Wilt Resistance in Blueberry Species

ABSTRACT Blueberry production is expanding rapidly in the United States and globally. In 2016, bacterial wilt was discovered in Florida blueberry production. Because of the international movement of plants, this disease poses a significant risk to production. The purpose of this project was to evaluate the resistance of blueberry species and cultivars to the three genetically distinct populations of Ralstonia identified in Florida blueberry production. Nineteen cultivars/species of Vaccinium were used in this study. Plants were selected from wild, northern, southern, midbush, lowbush, and rabbiteye varieties. Plants were inoculated with three genetically distinct strains of the pathogen, and experiments were replicated three times. Varying levels of quantitative (multigenic) bacterial wilt resistance were observed among varieties tested, with rabbiteye cultivars being the most resistant. These results are similar to bacterial wilt resistance observed in other agronomic crops. We also observed a unique specific qualitative (vertical) resistance in the rabbiteye cultivar ´Ochlockonee’. The pathogen was unable to colonize plant tissue and cause disease on this cultivar. This is the first report of qualitative resistance to Ralstonia solanacearum in blueberry. Both the multigenic and vertical resistance can be incorporated into blueberry breeding programs to mitigate potential losses to bacterial wilt.

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.

A More Drought Resistant Stem Xylem of Southern Highbush Than Rabbiteye Blueberry Is Linked to Its Anatomy

Increasing extreme drought events due to climate change may cause severe damage to blueberry industries, including decreased fruit yield and quality. Previous studies on drought tolerance of blueberries focus mainly on functional changes of leaves, while hydraulic properties of blueberry stems related to drought resistance are poorly reported. Here, both xylem anatomical and functional traits of stems of two southern highbush (SHB) and three rabbiteye blueberry (REB) cultivars were investigated. Compared with REB, SHB showed lower sapwood hydraulic conductivity (KS) and P50 (xylem water potential with 50% embolism in xylem), suggesting that SHB has less conductive but safer xylem than REB. The hydraulic functional differences between two blueberry xylems were highly related to their significant differences in vessel anatomy. Small vessel diameter and total inner pit aperture area per vessel area (APA) limited the hydraulic conductivity of SHB xylem, but high conduit wall reinforcement, wood density, and vessel-grouping index in SHB xylem showed strong mechanical support and safe water transport. Besides, pseudo-tori pit membranes were found in all five cultivars, while the similar thickness of homogenous pit membrane in two blueberry species was not linked to other functional traits, which may be due to its limited measurements. These results reveal a trade-off between the water transport efficiency and safety in the blueberry xylem and clarify the variance of stem drought resistance in different cultivars from a hydraulic perspective. Further studies with such a perspective on other organs of blueberries are required to understand the drought tolerance of a whole plant, which builds a solid foundation for the introduction, cultivation, and management of blueberry industries.

Identification of Fungi in the Botryosphaeriaceae Family Associated with Stem Blight of Vaccinium spp. in the Southeastern United States

Stem blight is a major disease of blueberry caused by Botryosphaeriaceae fungi. Chemical and cultural management options are limited, putting emphasis on breeding efforts to identify sources of resistance. The efficacy and durability of host resistance could be impacted by the species composition of the pathogen population in a region and by the isolates employed in the screenings used to identify the resistance. Samples (365) were collected from southern highbush (SHB) and rabbiteye blueberry (REB) cultivars from 28 sites in the southeastern US (AL, FL, GA, NC, and SC). Colony morphology identified 86% of the isolates as Botryosphaeriaceae. Conidia morphology and Maximum Likelihood analysis of the Internal Transcribed Spacer rDNA regions (ITS), translation elongation factor one alpha (tef1-α), and β-tubulin were used to identify isolates at genera or species level. A PCR-restriction fragment length polymorphism (PCR-RFLP) test was used to identify isolates to genus. Neofusicoccum and Lasiodiplodia were the predominant genera. N. kwambonambiense, N. ribis, L. theobromae and L. pseudotheobromae were the most common species isolated. Phylogenies conducted with a limited number of isolates indicated non-clonal and potentially diverse populations occur on blueberry that warrant additional study. Botryosphaeria corticis, B. dothidea, and Diplodia seriata were isolated infrequently.

Melatonin affects cuticular wax profile in rabbiteye blueberry (Vaccinium ashei) during fruit development

Cuticular wax has been implicated in the first line of plant defense mechanism against external stresses. In this study, cuticular wax on the fruits of two rabbiteye blueberry cultivars cv. Baldwin and Brightwell were examined in terms of the morphology and chemical composition during fruit development in the presence and absence of pre-harvest melatonin (MT) treatment. It revealed that the crystal wax appeared as numerous tubules, and its morphology was not affected by MT treatment. A dominant constituent of triterpenoid at veraison stage was β-amyrin (45.62% of total wax) in Baldwin and oleanolic acid (22.79% of total wax) in Brightwell. Exogenous MT application significantly promoted fruit quality and increased total content of cuticular wax, however, the effect of MT on individual wax components greatly varied depending on cultivars and fruit developmental stage. Consequently, MT application may enhance sustainability of post-harvest fruit production systems by facilitating accumulation of cuticular wax.

Micropropagation of Vaccinium virgatum ‘Delite’: a rabbiteye cultivar adapted to mild winters

ABSTRACT Blueberries have large amounts of antioxidant and anti-inflammatory compounds, playing an important role in improving health. In vitro culture is a possible method for vegetative propagation overcoming the problems of pathogen infection. Most studies on the in vitro culture of blueberries focus on highbush and lowbush cultivars. However, blueberry rabbiteye cultivars have lower chilling requirements and are more adapted to mild winter regions. Our objective was to develop a micropropagation protocol through axillary shoot growth, with reduced risks of somaclonal variation in ‘Delite’ rabbiteye blueberry. In vitro establishment was tested with single-node segments. The most promising results were using 2.5 µM zeatin. Multiplication through axillary shoot growth, starting with two-node stem segments were more successful in the concentration of 2.5 µM zeatin (70% of explants with axillary shoot growth). In vitro and ex vitro rooting with acclimatization were compared. In vitro rooting was achieved with immersion in 500 mg L−1 IBA (indole-3-butyric acid). Different substrates and mineral salts were also compared in ex vitro rooting. The results in vermiculite with WPM mineral salts were superior (68% rooting). In conclusion, this study provides techniques for micropropagation through axillary shoots of ‘Delite’ rabbiteye blueberry concerning establishment, multiplication, rooting, and acclimatization of plants.

Total Anthocyanin Content, Total Phenolic Content, and Antioxidant Activity of Various Blueberry Cultivars Grown in Togane, Chiba Prefecture, Japan.

More than fifty cultivated varieties of blueberries are grown under the same processing conditions on the farm at Chiba Prefectural Agricultural College in Japan. The fruits from 51 blueberry cultivars, including 16 rabbiteye (RE) cultivars (Vaccinium ashei Reade) and 35 highbush (HB) cultivars (Vaccinium corybosum L.), were evaluated for total anthocyanin contents, phenolic contents, and their contribution to antioxidant activity among cultivars. Total anthocyanin contents varied from 0.74±0.21 ("Barkley") to 4.27±0.18 ("Suwannee") mg as cyanidin-3-glucoside (Cy-3-GC) equivalent/g fresh-weight (fw), with phenolic contents in the range of 0.77±0.14 ("Floridablue") to 3.69±0.89 ("Suwannee") mg of gallic acid equivalent (GAE)/g fw, which strongly correlated with antioxidant activities assessed using the DPPH and ORAC methods, respectively. Total anthocyanin and phenolic contents were both significantly higher (p<0.05) in RE blueberries than in HB blueberries. Furthermore, the total phenolic values were significantly higher for the RE family than for the HB family (p<0.01). In comparisons of two species, the major anthocyanidin identified were malvidin in RE blueberries and delphinidin in HB blueberries. This result suggests that some RE blueberries, especially "Suwannee," "Homebell" and "Climax," are suitable supply sources with high in vitro antioxidant capacity. This study would be helpful to the quality-oriented cultivation of blueberry.

A comparative analysis on the anthocyanin composition of 74 blueberry cultivars from China

Blueberries are rich in anthocyanins and studied for their numerous beneficial effects on human health. The present study aimed to evaluate the anthocyanin composition of 74 blueberries collected in the south of China as well as analyze the phytochemical relationships among cultivars. Rabbiteye, southern highbush, northern highbush, half-highbush and lowbush blueberry cultivars were analyzed. Delphinidin, cyanidin, petunidin, and malvidin had three glycoside forms including galactoside, glucoside, and arabinoside, while peonidin had only galactoside form. The anthocyanin profile was similar among cultivars but amounts of individual compound differed. Malvidin, delphinidin and petunidin were the major contributors to total anthocyanin content (TAC), and malvidin-3-O-galactoside had the highest content among the 74 blueberry cultivars. Gardenblue had the highest TAC (2,235.51 ± 54.18 μg cyanidin 3-glucoside equivalent g−1 wet weight). In general, rabbiteye had significantly higher TAC than other categories analyzed in this study.

Dormancy of Floral Buds of Rabbiteye Blueberry in a Mild Winter Climate

HIGHLIGHTS This work studies the dormancy dynamics of blueberries growing in mild winter regions. The four rabbiteye blueberry cultivars meet the chilling requirements in the study. The floral buds of 'Delite' are more precocious than the other cultivars. Insights on how temperate fruit species could behave in warming climate scenarios.

Morphological and anatomical insights into de novo shoot organogenesis of in vitro ‘Delite’ rabbiteye blueberries

Blueberries are valued for their taste and their high nutritional benefits, including their antioxidant and anti-inflammatory properties. In vitro culturing is an alternative method for clonal propagation, and has been used in many biotechnological studies. Most blueberry research is concentrated on highbush and lowbush taxa (Vaccinium corymbosum and Vaccinium angustifolium respectively), with only limited investigations of rabbiteye cultivars (Vaccinium virgatum) that are more suitable for subtropical climates and regions with warmer winters as a result of climate change. There is therefore a need to determine in vitro protocols for that species and group of cultivars. We examined here adventitious shoot regeneration in the ‘Delite’ rabbiteye blueberry cultivar. Leaf explants were cultured in vitro in Woody Plant Medium (WPM), and the effects of different thidiazuron (TDZ) concentrations, the orientation of the leaf (adaxial or abaxial surface in contact with the medium), and two portions of the leaf segment (basal or apical) were examined. De novo shoot development was studied using light and scanning electron microscopy. All concentrations of TDZ used showed similar survival and regeneration rates; 0.5 μM TDZ showed high efficiency in regenerating adventitious shoots (100%, with 57 adventitious shoots/explant), as did the adaxial surface in contact with the medium using either the apical or the basal portion of the leaf (97% shoot regeneration, 47.5 adventitious shoots/explant). Anatomical analyses showed direct and indirect organogenesis. The shoots developed leaf primordia with stomata, trichomes, and well-developed vascular tissues, with further elongation and rooting of the plants. We therefore describe here a high-efficiency regeneration method through de novo shoot organogenesis using TDZ in foliar explants of rabbiteye blueberry, with direct and indirect organogenesis.

Self‐compatible blueberry cultivars require fewer floral visits to maximize fruit production than a partially self‐incompatible cultivar

Abstract Effective pollination is a complex phenomenon determined by the outcome of the interaction between pollen transfer and a plants' pollinator dependency, yet most studies investigate pollinator effectiveness without consideration of plant mating system differences. We investigated pollinator effectiveness in three types of blueberry that differed in their degree of pollinator dependency as measured by plant mating system: two self‐compatible highbush cultivars and one partially self‐incompatible rabbiteye cultivar. We quantified pollinator effectiveness as a function of the fruit set and fruit weight resulting from single and multiple floral visits (2–15 visits), in comparison with estimates of fruit set and fruit weight resulting from experimental pollination treatments (open‐pollination, cross‐pollination and self‐pollination). Single‐visit effectiveness of fruit set was similar across pollinator taxa but considerably higher in both self‐compatible cultivars. The probability of fruit set in all three blueberry types improved in response to an increasing number of visits, but this relationship was steeper in self‐compatible cultivars: &gt;90% probability of fruit set was achieved in three to five visits. In the self‐incompatible rabbiteye cultivar, 58% fruit set was achieved with 15 visits. Multiple visits improved fruit weight by 27%–48% in self‐compatible cultivars, but there was no relationship in rabbiteye. Pollination deficits in fruit set and fruit weight due to self‐pollination were most pronounced in rabbiteye. Synthesis and applications. Improved understanding of cultivar‐level mating system differences in plants will inform pollination planning and management in agroecosystems. Self‐compatible (highbush) cultivars require less floral visitation to maximize fruit production. Therefore, these cultivars may be best suited to landscapes in which pollinator abundance is low, such as intensive and/or simple landscapes. In contrast, self‐incompatible (rabbiteye) cultivars may benefit from the implementation of mixed‐cultivar crop row plantings to facilitate cross‐pollination.

Genomic insight into the developmental history of southern highbush blueberry populations.

Interspecific hybridization is a common breeding approach for introducing novel traits and genetic diversity to breeding populations. Southern highbush blueberry (SHB) is a blueberry cultivar group that has been intensively bred over the last 60 years. Specifically, it was developed by multiple interspecific crosses between northern highbush blueberry [NHB, Vaccinium corymbosum L. (2n = 4x = 48)] and low-chill Vaccinium species to expand the geographic limits of highbush blueberry production. In this study, we genotyped polyploid blueberries, including 105 SHB, 17 NHB, and 10 rabbiteye blueberry (RE) (Vaccinium virgatum Aiton), from the accessions planted at Poplarville, Mississippi, and accessions distributed in Japan, based on the double-digest restriction site-associated DNA sequencing. The genome-wide SNP data clearly indicated that RE cultivars were genetically distinct from SHB and NHB cultivars, whereas NHB and SHB were genetically indistinguishable. The population structure results appeared to reflect the differences in the allele selection strategies that breeders used for developing germplasm adapted to local climates. The genotype data implied that there are no or very few genomic segments that were commonly introgressed from low-chill Vaccinium species to the SHB genome. Principal component analysis-based outlier detection analysis found a few loci associated with a variable that could partially differentiate NHB and SHB. These SNP loci were detected in Mb-scale haplotype blocks and may be close to the functional genes related to SHB development. Collectively, the data generated in this study suggest a polygenic adaptation of SHB to the southern climate, and may be relevant for future population-scale genome-wide analyses of blueberry.

Volatile composition of eight blueberry cultivars and their relationship with sensory attributes

AbstractThe volatile compositions of eight blueberry cultivars (‘Premier’, ‘Gardenblue’, ‘Legacy’, ‘Brigitta’, ‘Misty’, ‘O’Neal’, ‘Bluerain’ and ‘Northland’) grown in the middle region of China were investigated. Volatiles were extracted by headspace solid‐phase microextraction (HS‐SPME) and analysed by gas chromatography—quadrupole time of flight—mass spectrometry (SPME‐GC‐QTOF‐MS). A total of 28 volatiles were identified and quantified, including 5 esters, 11 terpenoids, 3 aldehydes, 6 alcohols and 3 volatile phenols. Different blueberry cultivars had distinct varietal volatile profiles. Rabbiteye cultivars, ‘Premier’ and ‘Gardenblue’, were characterized by a large amount of esters, especially for ethyl acetate. ‘Misty’ had the highest terpenoid content. Principal component analysis (PCA) and partial least squares regression (PLS) were selected to correlate the chemical data with sensory perceptions. PCA showed that esters were dominant in rabbiteye blueberries, especially for ethyl acetate. No distinct pattern of volatile profile was found for the highbush and half‐highbush blueberry cultivars. PLS showed that the grassy descriptor was positively correlated with linalool and hexanal. The minty descriptor was positively correlated with eucalyptol.

The productivity of some southern highbush and rabbiteye blueberry cultivars under Turkey conditions

The productivity of some southern highbush and rabbiteye blueberry cultivars under Turkey conditions

Transcriptome analysis and annotation: SNPs identified from single copy annotated unigenes of three polyploid blueberry crops.

Blueberry is a kind of new rising popular perennial fruit with high healthful quality. It is of utmost importance to develop new blueberry varieties for different climatic zones to satisfy the demand of people in the world. Molecular marker assisted breeding is believed to be an ideal method for the development of new blueberry varieties for its shorter breeding cycle than the conventional breeding. Simple sequence repeats (SSRs) and single nucleotide polymorphisms (SNPs) markers are widely used molecular tools for marker assisted breeding, which could be detected at large scale by the transcriptome sequencing. Here, we sequenced the leaves transcriptome of 19 rabbiteye (Vaccinium ashei Reade), 13 southern highbush (Vaccinium. corymbosum L × native southern Vaccinium Spp) and 22 cultivars of northern highbush blueberry (Vaccinium corymbosum L) by using next generation sequencing technologies. A total of 80.825 Gb clean data with an average of about 12.525 million reads per cultivar were obtained. We assembled 58,968, 55,973 and 53,887 unigenes by using the clean data from rabbiteye, southern highbush and northern highbush blueberry cultivars, respectively. Among these unigenes, 3599, 3495 and 3513 unigenes were detected as candidate resistance genes in three blueberry crops. Moreover, we identified more than 8756, 9020, and 9198 SSR markers from these unigenes, and 7665, 4861, 13,063 SNPs from the annotated single copy unigenes, respectively. The results will be helpful for the molecular genetics and association analysis of blueberry and the basic molecular information of pest and disease resistance of blueberry, and would also offer huge number of molecular tools for the marker assisted breeding to produce blueberry cultivars with different adaptive characteristics.

Tolerance of southern highbush and rabbiteye blueberry cultivars to saflufenacil

AbstractGreenhouse and field studies were conducted to determine tolerance of blueberry to saflufenacil. Greenhouse studies included five saflufenacil rates (0, 50, 100, 200, and 400 g ai ha−1) and three southern highbush blueberry cultivars (‘Legacy’, ‘New Hanover’, and ‘O’Neal’) and one rabbiteye blueberry cultivar (‘Columbus’). Saflufenacil treatments were soil applied into each pot when blueberry plants were approximately 30-cm tall. Visible injury (purpling/reddening of foliage and leaf abscission) ranged from 3% to 12%, 3% to 42%, 0% to 43%, and 0% to 29% with saflufenacil from 50 to 400 g ha−1 in Columbus, Legacy, New Hanover, and O’Neal, respectively, at 28 d after treatment. Regardless of injury, plant growth (change in height), soil plant analysis development, and whole-plant dry biomass of all cultivars did not differ among saflufenacil rates. Field studies were conducted in Burgaw, NC, to determine the tolerance of nonbearing (&amp;lt;3-yr-old and not mature enough to produce fruit) and bearing (&amp;gt;3-yr-old and mature enough to produce fruit) southern highbush blueberry (‘Duke’) to saflufenacil application at pre-budbreak or during the vegetative growth stage. Treatments included three rates of saflufenacil (50, 100, and 200 g ha−1), glyphosate (870 g ae ha−1), glufosinate (1096 g ai ha−1), glyphosate (870 g ha−1) + saflufenacil (50 g ha−1), glufosinate (1096 g ha−1) + saflufenacil (50 g ha−1), and hexazinone (1,120 g ai ha−1), applied POST-directed to the soil surface beneath blueberry plants in a 76-cm band on both sides of the blueberry planting row. The maximum injury from treatments containing saflufenacil was ≤11% in both nonbearing and bearing blueberry. No negative effects on plant growth or fruit yield were observed from any treatments. Results from both greenhouse and field studies suggest that saflufenacil applied at 50 (1X commercial use rate) and 100 g ha−1 is safe to use in blueberry.

Changes in phenolic profiles and antioxidant activity in rabbiteye blueberries during ripening

ABSTRACTBlueberry (Vaccinium spp.) is a widely consumed fruit worldwide. Anthocyanins, phenolic acids, and flavonoids are the main bioactive compounds of blueberry. However, little information is available about the changes in phenolic profiles of blueberries during fruit maturation. The aim of this work was to assess the effects of genotype and maturity on phenolic compounds and antioxidant ability of four rabbiteye blueberry cultivars grown in Guizhou, China. The total phenolics, total flavonoid and individual phenolic compound in the rabbiteye blueberries were investigated at five ripening stages based on color. Derivatives of phenolic compounds (gallic acid, epicatechin, rutin, p-coumaric acid, quercetin, catechin, ellagic acid, chlorogenic acid, and ferulic acid) were determined by HLPC and quantified using calibration curves. Antioxidant capacity was evaluated by total reducing power assay (TRPA), 1,1-diphenyl-2- picrylhydrazyl (DPPH), ferric ion reducing antioxidant power (FRAP), and 2,2ʹ-Azinobis-(3-ethylbenzthiazoline-6-sulfonate (ABTS) assay. Gallic acid, ellagic acid, and ferulic acid were the main phenolic compounds in rabbiteye blueberries, and phenolic compound contents of different rabbiteye blueberries cultivars changed with ripening stage. The gallic acid content of all cultivars increased at first and then decreased. The ferulic acid contents of ‘Powderblue’ and ‘Gardenblue’ cultivars gradually increased during ripening. The ellagic acid content of ‘Powderblue’ blueberries increased with ripening but decreased in ‘Baldwin’ blueberries. The total phenolics, total flavonoid, and antioxidant capacity of all cultivars increased nonlinearly with ripening. Phenolic compounds were the main antioxidants found in rabbiteye blueberries. Notably, ‘Gardenblue’ had exceptionally higher phenolics compound and antioxidant activity compared with other cultivars.