Rabbiteye Blueberry Cultivars Research Articles

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.

Phylogenetic relationship and genetic background of blueberry (Vaccinium spp.) based on retrotransposon-based SSAP molecular markers

A total length of 98 070 bp long terminal repeat retrotransposon (LTR-RT) sequences were found after preliminary prediction and subsequent screening, accounting for 3.96% of the whole blueberry genome. Thirty-three members belonged to Ty1/Copia retrotransposon family and 60 members of Ty3/Gypsy retrotransposon family were identified according to their sequence similarity to previously reported retrotransposons, accounting for 1.57% and 2.39% of the whole genome, respectively. Nineteen sequences from Ty1/Copia family and thirty-three Ty3/Gypsy sequences were used for primer design. Sixty-six pairs of primers were synthesized randomly, in which forty-two pairs of primers were screened to validate the availability and transferability of LTR-RT on 48 blueberry cultivars. We found that 4, 236 bands were amplified using 42 pairs of primers, of which 4184 were polymorphic bands. Bands at each locus ranged from 34 to 219, with an average of 101. To elucidate genetic relationship of 48 blueberry cultivars, principle coordinate analysis (PCoA) was carried out based on SSAP genotyping data. The results showed that the first two coordinates could explain 14.11% of the total variation among all cultivars, of which the first and second coordinate accounted for 8.13% and 5.98% of total variation, respectively. The first three axes accounted for 18.84% of the total variation. In order to estimate genetic background and phylogenetic relationship of these cultivars, phylogenetic tree was constructed based on neighbor-joining algorithm. The results showed that 48 cultivars could be clustered into five groups, indicating that genetic background of 48 blueberry cultivars used in this study was relatively simple. The genetic composition of highbush blueberry cultivars was similar, which consisted of a single genepool. Genetic background of rabbiteye blueberry cultivars presented multiple source of genepools, which was probably related to the involvement of several species in the artificial selection. ‘Bluegem’ resembles genetic composition with highbush blueberries, suggesting that several cultivars possibly involved in its breeding process. The original lineage from V. virgatum was supposed to be replaced gradually with repeated hybridization during cross fertilization. The cross breeding among cultivars genetically distant from one other would enrich the genetic diversity of blueberry cultivars. All these results provided valuable references for the selection of parental cultivars in blueberry breeding.

The Effect of Ethephon, Abscisic Acid, and Methyl Jasmonate on Fruit Ripening in Rabbiteye Blueberry (Vaccinium virgatum)

Ripening in blueberry fruit is irregular and occurs over an extended period requiring multiple harvests, thereby increasing the cost of production. Several phytohormones contribute to the regulation of fruit ripening. Certain plant growth regulators (PGRs) can alter the content, perception, or action of these phytohormones, potentially accelerating fruit ripening and concentrating the ripening period. The effects of three such PGRs—ethephon, abscisic acid, and methyl jasmonate—on fruit ripening were evaluated in the rabbiteye blueberry (Vaccinium virgatum) cultivars ‘Premier’ and ‘Powderblue’. Application of ethephon, an ethylene-releasing PGR, at 250 mg L−1 when 30–40% of fruit on the plant were ripe, accelerated ripening by increasing the proportion of blue (ripe) fruit by 1.5–1.8-fold within 4 to 7 days after treatment in both cultivars. Ethephon applications did not generally alter fruit quality characteristics at harvest or during postharvest storage, except for a slight decrease in juice pH at 1 day of postharvest storage and an increase in fruit firmness and titratable acidity after 15 days of postharvest storage in Powderblue. In Premier, ethephon applications decreased the proportion of defective fruit at 29 days of postharvest storage. Abscisic acid (600–1000 mg L−1) and methyl jasmonate (0.5–1 mM) applications did not alter the proportion of ripe fruit in either cultivar. These applications also had little effect on fruit quality characteristics at harvest and during postharvest storage. None of the above PGR applications affected the development of naturally occurring postharvest pathogens during storage. Together, data from this study indicated that ethephon has the potential to accelerate ripening in rabbiteye blueberry fruit, allowing for a potential decrease in the number of fruit harvests.

Growth, flowering and fruiting behaviour of different blueberry (Vaccinium spp) genotypes under mid hill conditions of Himachal Pradesh, India

Four southern highbush blueberry (Vaccinium spp. ) cultivars, viz. Jewel, Misty, Gulf Coast and Sharpblue along with Austin, and Alapaha (Rabbiteye) were studied for their vegetative growth, flowering and fruiting behaviour at CSKHPKV, Palampur, Himachal Pradesh during the year 2015-16. A significant variation was observed for annual shoots/cane growth and growth pattern among these genotypes. Southern highbush cultivar Jewel produced maximum (49.05 cm) shoots/cane length with vigorous growth, closely followed by a rabbiteye cultivar cv. Austin (48.36 cm) and minimum shoot growth (39.02 cm) was observed in Alapaha. The growth rate at different interval was also recorded and it was observed maximum at D2-3 intervals in all genotypes.The results also showed significant variation with respect to various foliar characters, viz. leaf size, specific leaf area, number of flowers/cluster, corolla size (length and breadth), number of stamens/flower and color of corolla. All southern highbush blueberry cultivars were earliest to flower as compared to rabbiteye. Similarly, a significant variation was observed for number of flowers and fruits/cluster among genotypes. Gulf Coast had maximum (8.78 flowers/cluster) number of flowers/cluster followed by Jewel (7.67 flowers/cluster) another southern highbush blueberry cultivar. The harvesting of southern highbush cultivars, viz. Misty and Gulf Coast was earliest among other genotypes and both rabbiteye blueberries the harvesting was late starting from 21 May in Alapaha and 27 May in Austin. However, the yield of individual cultivars was not recorded but cumulative yield at the end of harvesting it was observed to be 200-250 g/bush (data not presented). The southern highbush blueberries such as Jewel, Misty, Gulf Coast and Sharpblue have shown encouraging results with satisfactory growth, flowering and fruiting thus they can be grown in Himachal Pradesh and areas prevailing similar agroclimatic conditions in India.

Assessment of Newly Released and Well-Established Rabbiteye Blueberry ( <i>Vaccinium ashei </i>Reade) Cultivars in North Alabama

Many cultivars of rabbiteye blueberry (Vaccinium ashei Reade) have been recently developed with diverse vegetative and cropping characteristics, but scientific data on their performance in Alabama is limited. An experiment was established at the North Alabama Horticulture Research Center, Cullman, AL (lat. 34°11'N, long. -86°47'E), USDA Hardiness Zone 7B, to evaluate the performance and horticultural value of the following rabbiteye blueberry cultivars: “Alapaha”, “Baldwin”, “Brightwell”, “Climax”, “Ira”, “Montgomery”, “Onslow”, “Powderblue”, “Premier”, “Tifblue”, and “Yadkin”. Cultivar flowering and ripening season, yield potential, fruit quality characteristics, and vegetative growth were investigated during 2009 and 2010. “Alapaha”, “Climax”, and “Premier” were found to have early ripening in north Alabama. “Alapaha” flowered later than the earliest flowering cultivars, but ripened consistently early, and this later flowering can serve to protect “Alapaha” crop from late freeze damage. Cultivars were not found to differ with respect to their cumulative yield in their fifth and sixth leaf. “Brightwell” and “Climax” had the firmest berries, while “Climax” and “Premier” had the sweetest berries.

Evaluation of fruit quality traits in southern highbush and rabbiteye blueberries

The two main blueberry types grown in Georgia are southern highbush (species complex between Vaccinium corymbosum L. and V. darrowii Camp) and rabbiteye (V. virgatum Aiton). In 2014, both blueberry types accounted for over 44,400 metric tons in 6,475 ha, making Georgia the number two producer in the United States. Southern highbush and rabbiteye blueberries are rarely thought to have similar fruit quality characteristics, although there is a limited amount of information available on cultivars that are currently grown. The objective of this research was to examine physical and chemical fruit quality attributes of southern highbush and rabbiteye blueberry cultivars that currently compose the majority of the commercial blueberry market in Georgia. Seven southern highbush cultivars: 'Camellia', 'Emerald', 'Farthing', 'Legacy', 'Meadowlark', 'Rebel', and 'Star'; and seven rabbiteye cultivars: 'Alapaha', 'Brightwell', 'Ochlockonee', 'Powderblue', 'Premier', 'Tifblue', and 'Vernon' were grown and harvested at approximately 50% ripe at the University of Georgia Blueberry Research Farm near Alapaha, GA in 2014. Physical characteristics evaluated included: skin strength (puncture) and berry firmness (Kramer Shear). Chemical characteristics evaluated included: sugar profile and fiber (NDF and ADF). Overall, there was not a significant difference between highbush and rabbiteye blueberries for skin strength, however, rabbiteyes had firmer fruit than highbush blueberries (P‹0.05). For sugars, rabbiteyes were significantly higher than southern highbush for °Brix, sucrose, and total sugar. However, no significant differences were observed between types for glucose and fructose. For fiber, rabbiteyes were significantly higher than southern highbush for NDF, ADF, and lignin content. Results from this study will be compared with subsequent seasons to further understand these quality traits.

Blueberry Cultivar Identification Using Random Amplified Polymorphic DNA and Sequence-characterized Amplified Region Markers

Blueberry cultivars have traditionally been identified based on the evaluation of sets of morphological characters; however, distinguishing closely related cultivars remains difficult. In the present study, we developed DNA markers for the genetic fingerprinting of 45 blueberry cultivars, including 31 cultivars introduced from the United States Department of Agriculture. We obtained 210 random amplified of polymorphic DNA (RAPD) markers using 43 different primers. The number of polymorphic bands ranged from three (OPG-10 and OPQ-04) to eight (OPR-16), with an average of five. A cluster analysis performed with the unweighted pair group method using arithmetic averages produced genetic similarity values among the blueberry cultivars ranging from 0.53 to 0.85, with an average similarity of 0.68. A dendrogram clustered the 45 blueberry cultivars into two main clusters, with a similarity value of 0.65. Cluster I consisted of four rabbiteye cultivars (Pink Lemonade, Alapaha, Titan, and Vernon) and the Ashworth northern highbush cultivar. Cluster II consisted of 31 northern highbush cultivars, eight southern highbush blueberry cultivars, and Northland half-highbush blueberry cultivar. Fifty five RAPD fragments selected were sequenced to develop sequence-characterized amplified region (SCAR) markers, resulting in the successful conversion of 16 of 55 fragments into SCAR markers. An amplified polymorphic band has the same size as the RAPD fragment or smaller according to the primer combinations in the 16 SCAR markers. Among these markers, a combination of 11 SCAR markers provided sufficient polymorphisms to distinguish the blueberry cultivars investigated in this study. These newly developed markers could be a fast and reliable tool to identify blueberry cultivars.

Novel formulation of gibberellic acid and coconut oil fatty acids to enhance rabbiteye blueberry maturation, berry size, and yield: a review

This review paper provides a summary of results presented in a much more comprehensive article (Sampson et al., 2014). Specifics regarding methods and statistical procedures can be found in Sampson et al. (2014). Here, we summarize these results for popular cultivars of rabbiteye blueberry (V. virgatum syn. ashei Reade) that produce upwards of 90% deformed “zygomorphic” blooms as well as other cultivars that do not. One cultivar in particular, 'Premier', by producing zygomorphic blooms, suffers losses in yield. Infertility of these zygomorphs might render plants less fruitful with yield losses reaching 67%. Other vulnerable rabbiteye blueberry cultivars include 'Columbus', 'Yadkin', 'Montgomery', and 'Tifblue'. To ensure zygomorphic cultivars remain fruitful, blooms dosed with gibberellin A3 (GA3) can achieve exceptionally high sets of small seedless fruit that mature 7-14 days late. Our new GA3 formulation, which combines gibberellic acid with 0.05% coconut oil (or 5% coconut oil soap), yielded seedier faster-maturing berries rich in sugar (10 to 12% dissolved solids). Seeds appear to have arisen via apomixis perhaps induced by bioactivity of longer-chained fatty acids and cytokinins in coconut oil. Seed size for apomictic fruits varied considerably; a few seeds were as large as those resulting from cross-pollination; most seeds were 3-4 times smaller in volume. Coconut fatty acids therefore function as possible synergists to GA3, producing marketable seeded berries.

Effects of inoculation with ericoid mycorrhizal fungi on leaf nutrients of two field-grown rabbiteye blueberry cultivars

Effects of inoculation with ericoid mycorrhizal fungi on leaf nutrients of two field-grown rabbiteye blueberry cultivars

Performance of blueberry cultivars under mild winter conditions

ABSTRACT: Evaluation of yield performance is important to find the most adapted blueberry cultivars in a particular region. This research aimed to evaluate the flowering and hasvesting periods, the production per plant, and fruit quality of eight rabbiteye blueberry cultivars (Aliceblue, Bluebelle, Bluegem, Briteblue, Climax, Delite, Powderblue, and Woodard) and two highbush blueberries (Georgiagem and O’Neal), in mild winter conditions in Pinhais-PR. Flowering and harvesting periods, production, berry weight, size, pH, soluble solids, titratable acidity, ratio and color of the fruits were evaluated in the 2013/2014 and 2014/2015 growing seasons, when the plants had two and three years old, respectively. Cultivars flowered from August to September, and harvest was concentrated in November and December. Berry weight, size, pH, soluble solids and acidity varied among the cultivars. The average ratios of 14.97 and 13.39 for each crop proved that the cultivars have good fruit quality. There was little variation in fruit color in the two years evaluated. Blueberry cultivars showed the staining characteristics and physical and chemical attributes of quality compatible to blueberry from other traditional regions. Under mild winter conditions, young plants of rabbiteye blueberry cultivars, Climax, Delite, Bluegem and Powderblue, are the most productive, while the highbusch cultivars bear few fruits.

In vitro screening and evaluation of phenolic antioxidant-linked anti-hyperglycemic functions of rabbit-eye blueberry (Vaccinium ashei) cultivars

In vitro screening and evaluation of phenolic antioxidant-linked anti-hyperglycemic functions of rabbit-eye blueberry (Vaccinium ashei) cultivars

Plant cultivars imprint the rhizosphere bacterial community composition and association networks

Rhizosphere associated microbiota is of the central importance for modulating plant growth and health. To comprehensively understand the genetic principles governing the composition and co-occurrence patterns of the rhizosphere microbiota, the bacterial communities in the rhizospheres of 12 rabbiteye blueberry (RB) cultivars along with their counterparts in the blackberry rhizosphere and bulk soil were characterized to assess the relative influence of edaphic properties and plant cultivars. The composition and network structure of bacterial community were examined using Illumina sequencing of 16S rRNA gene, coupled with co-occurrence networks analysis. The diversity and composition of rhizosphere bacteria community depended more on the interactions with the soil environment (pH and organic carbon) than with the host cultivars. The bacterial assemblages within the blueberry cultivars clearly clustered into three groups (BRI, BRII and RBIII). The bacterial community composition in RBIII, with a higher abundance of Gammaproteobacteria but a lower abundance of Alphaproteobacteria and Actinobacteria, remarkably differed from that in RBI and RBII. Rhizobiales and Pseudomonadaceae predominated in the obtained rhizosphere core microbiota within the plant cultivars. The rhizosphere from the plant cultivars exerted substantial effects on bacterial association networks and putative keystone species. Intra and inter-phylum/class co-occurrence in blueberry networks higher than expected by chance was induced by their common ecological niche differentiation or synergistic relationships. Taken together, a comprehensive understanding of the rhizosphere associated bacterial community structure and interaction networks is imperative to elucidate the biological mechanisms guiding bacterial assembly in the rhizosphere.

Antioxidant, free radical scavenging activities and total polyphenolic content of aqueous extracts from seven blueberry cultivars grown in New Zealand

ABSTRACT Antioxidant activity in blueberries or other fruits is an appealing characteristic to consumers and food industries. The antioxidant properties of aqueous extracts prepared from the berries of five rabbiteye (Vaccinium ashei) and two highbush (V. corymbosum) cultivars of blueberry grown in New Zealand, were studied using ferric reducing antioxidant power (FRAP) and scavenging DPPH (2, 2-diphenyl-1-picrylhydrazyl) free radical assays. Their ferrous ion chelating activities and total polyphenol contents (TPC) were also determined. Significant differences were found in antioxidant/antiradical activities and TPC among various cultivars of blueberries. The results showed that the highest TPC among the highbush cultivars were detected in the extracts from the berries of Jersey while the lowest TPC were detected in the extracts from the berries of Dixi. Similarly, the antioxidant/antiradical activity was significantly higher in Jersey than in Dixi cultivar which indicates that the antioxidant activity is related to the total phenolic contents. Among the rabbiteye cultivars, Centurion had the highest TPC followed by cultivars Maru, Rahi, Tifblue, and Ono. Regarding the antioxidant activity among the rabbiteye cultivars, it was in accordance with the results of TPC for all cultivars studied in that Centurion had the highest FRAP value and Ono cultivar had the lowest. A similar trend of activity was observed regarding the DPPH radical scavenging capacities. This may confirm that the phenolic compounds found in the blueberry extracts are the main contributors of the antioxidant/antiradical activities. In general, rabbiteye cultivars had significantly higher TPC (P < 0.01), higher antioxidant (P < 0.05) and free-radical scavenging activity (P < 0.05) than highbush cultivars.

Antimicrobial activity and differentiation of anthocyanin profiles of rabbiteye and highbush blueberries using HPLC–DAD–ESI-MSn and multivariate analysis

This study aims to perform in vitro analyses of the antimicrobial activity of ten blueberry cultivars, to characterize the anthocyanin composition of these fruits, and to use multivariate analysis to compare the results. All blueberry cultivars presented anti-Escherichia coli activity. Furthermore, the complete series of six glycosides (galactoside, glucoside, arabinoside, xyloside, acetylgalactoside and acetylglucoside) of five anthocyanidins (delphinidin, cyanidin, petunidin, peonidin, and malvidin) were detected, together with six malonyl derivatives of the main anthocyanins. The rabbiteye cultivars showed higher proportions of cyanidin 3-galactoside than the highbush cultivars, the latter accounting for higher proportions of the 3-arabinosides of delphinidin and malvidin. The total anthocyanin content was between 10.8 and 26.5 g/kg of dry weight, and the concentration depended on the size of the berries, with the smaller rabbiteye cultivars exhibiting higher levels of anthocyanins.

The Effect of Soil Texture on Fruits and Growth Properties in Rabbiteye Blueberries

This study was conducted to compare the plant growth and fruit quality of blueberries grown in different soil textures of Korea, in order to utilize the results for stable production and soil improvement. Rabbiteye blueberry cultivars 'Tifblue' and 'Baldwin' were planted and grown for three years from 2013 in wagner pot (1 <TEX>$2000a^{-1}$</TEX>) in a greenhouse of Namhae Sub-station, Institute of Horticultural and Herbal Science. The plants were grown in four soil textures, sand, sandy loam, loam and silt loam, and nutrient uptake and growth characteristics of plants were investigated. Leaf nitrogen and phosphorus contents of two cultivars grown in different soil textures ranged between 8.6 to <TEX>$10.5gkg^{-1}$</TEX>, which was lower than appropriate level for rabbiteye blueberry. However, the contents of potassium, calcium and magnesium in leaves were appropriate levels as <TEX>$2.29{\sim}3.62gkg^{-1}$</TEX>, <TEX>$4.46{\sim}5.46gkg^{-1}$</TEX> and <TEX>$1.45{\sim}2.12gkg^{-1}$</TEX>, respectively. Nitrogen and phosphate contents in leaves were higher in the two cultivars grown in silt loam soil. There was no significant difference in plant volume and root dry weight among four soil textures in two cultivars. However, dry weight of leaves and branches were highest in loam soil. Fruit production was highest in loam and silt loam soil in two cultivars, showing negative correlation with the amount of sand in soil. However, sugar and acidity showed no correlation with sand content in soil. These results show the limit to the blueberry growth in soil that has no nutrient holding capacity; however, most of Korean soils that have good nutrient holding capacity can produce competitive fruits if the drainage is improved.

Composition of phenolic compounds and antioxidant activity in the leaves of blueberry cultivars

Phenolic compounds in the leaves of 104 blueberry cultivars were investigated using HPLC–DAD and HPLC–ESI–MS2 analysis. This approach identified 28 constituents, among which eight constituents were identified certainly by authentic standards, while others were tentative. Three anthocyanins, four flavonols and four chlorogenic acids were reported for the first time in blueberry leaves. Furthermore, the antioxidant activity of blueberry leaves was estimated by using DPPH•, ABTS•+ and FRAP assays. It was found that most rabbiteye blueberry cultivars had higher antioxidant activity than most northern and southern highbush ones. The rabbiteye cultivars ‘Vernon’, ‘Britewell’ and ‘T-172, Festival’ appear to be good sources of antioxidants. Hierarchical cluster analysis classified 104 cultivars into three clusters, and they were distinct from each other. This study contributes to current knowledge on the composition of phenolic compounds in blueberry leaves, and identifies specific cultivars which may be potential resources for tea making and food additive.

래빗아이 블루베리 품종별 꽃눈의 내동성과 재배안전지역

Floral Bud Cold Hardiness and Cultural Safety Zone in Rabbiteye Blueberry Cultivars Hong-Lim Kim, Yong-Bum Kwack, Jeom-Hwa Han, Pill-Kyung Oh, Won-Byoung Chae, Seong-Cheol Kim, Mok-Jong Kim and Jin-Gook Kim, (Namhae Sub‐Station, NIHHS, RDA, Namhae 668‐812, Korea, Fruit Research Division, NIHHS, RDA, Suwon 440-706, Korea, Vegetable Research Division, NIHHS, RDA, Suwon 440‐706, Korea, Department of Horticulture, Gyeongsang National University, Jinju 660‐701, Korea)

Variation among highbush and rabbiteye cultivars of blueberry for fruit quality and phytochemical characteristics

Variability in soluble solids (SS), titratable acidity (TA), SS/TA, pH, total phenolic content (TPC), ferric reducing ability of plasma (FRAP), total monomeric anthocyanin content (TMAC) and levels of vitamin C were evaluated in a broad array of northern and southern highbush (Vaccinium corymbosum) and rabbiteye (Vaccinium virgatum) cultivars of blueberry, grown in different locations and years. When cultivars were grouped by decade of release, there were few significant overall trends observed over years in fruit quality and phytochemical content; however, individual cultivars varied significantly for all the traits analysed. Considerable overlap in most quality and phytochemical characteristics were found among cultivars of the three blueberry types, suggesting that genetic barriers do not exist among the various types of blueberries with regard to breeding cultivars with comparable sugar, acid and phytochemical properties. There were significant negative correlations observed between fruit weight and SS, TPC, FRAP and TMAC, suggesting that as breeders have been selecting for larger fruit, they have inadvertantly selected for tarter fruit with lower antioxidant capacity. However, SS was correlated positively with FRAP and TMAC, indicating that cultivars can be developed that have high antioxidant capacity and anthocyanin content, combined with high sugar content.

Stone Cell Frequency and Cell Area Variation of Crisp and Standard Texture Southern Highbush Blueberry Fruit

Sclerified stone cells with a thick and lignified secondary cell wall are known to vary in number among cultivars of northern highbush blueberry (Vaccinium corymbosum) and rabbiteye blueberry (Vaccinium virgatum), and may contribute to fruit texture. Variation in cell size can also contribute to differences in fruit firmness. Fruit from nine southern highbush blueberry [SHB (V. corymbosum interspecific hybrids)] cultivars determined by sensory and instrumental analysis to vary in fruit texture were harvested at mature green and ripe blue developmental stages. Paraffin embedded 12-μm sections were stained with Safranin O and Aniline Blue and microstructure was examined by light microscopy. Stone cells within ≈1.2 mm of the epidermis were counted and cell area was measured in the epidermal layer and three layers beneath the epidermis of the fruit. There was a significant difference in cell area among genotypes and cell layers for mature green fruit and among texture types, genotypes, and cell layers for ripe blue fruit. The average number of stone cells in a single berry ranged from zero to 95 among cultivars. Significant differences in the number of stone cells just below the epidermal layer did not correspond to standard or crisp fruit texture.

α-Glucosidase inhibitory activity and antioxidant capacity in the peel and pulp of mixed-species blueberry hybrids

Inhibition of α-glucosidase activity is considered an effective means for controlling diabetes by regulating glucose uptake, and blueberries have been shown to possess high levels of inhibitory activity. In the present study, we examined the variations in α-glucosidase inhibition, phenolic and anthocyanin levels, and antioxidant capacity in the peel and pulp of 16 mixed-species rabbiteye hybrids (Vaccinium asheiReade × Vacciniumspp.), one rabbiteye cultivar (V. ashei) and two highbush hybrids (Vaccinium corymbosum). Peel tissue had, on average, about four times higher levels of α-glucosidase inhibitory activity than pulp, and exhibited significantly higher levels of all other measured activities, even though the peel comprised only a small portion of the fruit. Significant variations in the levels of antioxidant activity were observed; however, no consistent differences were observed between the hybrids with various species composition. Significant positive correlations (r≥ 0.84) were found among α-glucosidase inhibitory activity, total anthocyanin (TA) and phenolic levels, and scavenging activity against ROO∙, ∙OH,1O2and H2O2radicals in the extracts from the peel and pulp. There was a high correlation observed between α-glucosidase inhibitory activity levels and ROO∙(ORAC)peel(r= 0.95). A similarly high correlation with TApeel(r= 0.93) suggests that TA would be a suitable assay proxy if a broader genotypic evaluation of blueberry genotypes is desired.