Blueberry Stem Research Articles

Modeling the Effect of Temperature on the Severity of Blueberry Stem Blight and Dieback with a Focus on Neofusicoccum parvum and Cultivar Susceptibility

Stem blight and dieback rank among the most relevant diseases affecting blueberry production worldwide. In Northern Italy, Neofusicoccum parvum, Diaporthe rudis, Cadophora luteo-olivacea and Peroneutypa scoparia have been reported to cause stem blight and dieback in blueberry. Considering that the incidence and severity of these diseases are on the rise in Northern Italy, two of the main aims of the present study were a—to compare the in vitro growth rate of the four fungi at different temperatures and b—to assess the aggressiveness of the same fungi on four commercial blueberry cultivars. Neofusicoccum parvum had the fastest growth rate and was the most aggressive pathogen. A possible effect of temperature on host colonization by N. parvum and disease expression was postulated and tested as a third aim. In planta trials were performed to model and predict the influence of temperature on the severity of blueberry stem blight and dieback caused by N. parvum. Increasing temperatures boosted the aggressiveness of the pathogen, causing higher disease severity and host mortality. Our findings suggest that temperature plays a relevant role in the severity of blueberry stem blight and dieback caused by N. parvum. Given the predictions of a warmer climate, this disease may become increasingly more significant and should be actively managed.

Evaluation of dichlobenil for hair fescue (Festuca filiformis Pourr.) management in wild blueberry (Vaccinium angustifolium Ait.)

AbstractHair fescue is an economically destructive, tuft‐forming weed common in wild blueberry fields. The current management of hair fescue is almost completely reliant on pronamide (3,5‐dichloro‐N‐[2‐methylbut‐3‐yn‐2‐yl]benzamide) herbicide with few other products demonstrating effectiveness. Dichlobenil (2,6‐dichlorobenzonitrile) is a group 29 herbicide registered for use in wild blueberry; however, it has seen limited use because of its high product cost of over CAD 1800 ha−1 and limited research on the effect of varying application rates. Treatments (dichlobenil at 4400, 5700, and 7000 g a.i. ha−1, pronamide at 2240 g a.i. ha−1, and a nontreated control) were applied during the 2020 autumn prior to wild blueberry stem emergence in the nonbearing year (2021). Each treatment was replicated five times per field across three fields in central Nova Scotia. Dichlobenil at 4400, 5700, and 7000 g a.i. ha−1 reduced 2021 (nonbearing year) living tuft density by 59%, 71%, and 83%, respectively, and provided residual control in 2022 (bearing year) with densities reduced by 59%, 69%, and 78%, respectively. Comparatively, pronamide reduced 2021 and 2022 living tuft density by 95% and 91%. Reductions in living tuft density resulted in yield increases of 62%, 57%, and 94% in plots treated with dichlobenil at 4400, 5700, and 7000 g a.i. ha−1, respectively, and 73% for plots treated with pronamide. Results demonstrate that dichlobenil is an effective herbicide for managing hair fescue in wild blueberry. The potential for the selection of herbicide‐resistant biotypes to industry standard pronamide could be prolonged with integrated dichlobenil applications.

First report of Diaporthe sojae causing stem canker on blueberry in China.

Blueberry (Vaccinium corymbosum) plants are popular all over the world due to their high nutritional value and health benefits. In October 2020, blueberry stems (cv. O'Neal) displaying reddish brown necrotic lesions were observed from a blueberry field in Anqing (Anhui, China), with the incidence of approximately 90%. The affected plants were somewhat stunted that had smaller fruit, and in severe cases, partial or whole plant died. We randomly selected three sampling sites to collect stems with the symptoms. Samples at the margin between diseased and healthy tissues were taken out, cut into 5 mm pieces in length，and then mixed them together. Twenty small samples were surface-sterilized, and plated onto potato dextrose agar (PDA). The plates were incubated at 25°C in the dark until fungal colonies were observed. After subculturing single hyphal tips, 9 out of 12 fungal isolates with similar morphologies were obtained. The representative isolate, LMKY12 was selected for further identification. The colonies on PDA showed white, fluffy aerial mycelia with 7.9  0.2 mm (n=5) diameter after inoculation in darkness at 25°C for one week. The colony darkens in color with age, yellowish pigmentation in reverse were observed. After 15 days of incubation, dark brown, irregular hard particles (fruiting bodies in sexual stage) accumulated on the surface of the colonies. Asci were 8-spored, sessile, club-like, hyaline, and 35-46 x 6-9 μm (n=30) in size. The ascospores were oval or spindle shaped, two-celled, constricted at division, and containing four guttulates with larger guttules at centre and smaller one at ends, measured 9-11 x 2-4 um (n=50). No sporulation observed on blueberry stems after inoculated 30 days. In order to induce the production of conidiophores, mycelial plugs were placed on blueberry leaves and cultured in darkness at 25°C. There are two types of conidia observed after 20 days of inoculation. Alpha conidia were aseptate, hyaline, smooth, ovate to ellipsoidal, often biguttulate, measured 5.33-7.26 x 1.65-2.53 μm (n=50). Beta conidia were hyaline, linear, measured 12.60-17.91 x 0.81-1.38 μm (n=30). The morphological characteristics matched the previous description of D. sojae (Udayanga et al. 2015; Guo et al. 2020). To confirm the identification, the mycelial genomic DNA of LMKY12 was extracted as a template. The rDNA internal transcribed spacer (ITS), translation elongation factor 1-α gene (TEF1-α), and calmodulin (CAL) were amplified and sequenced using primers ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R, and CAL-228F/CAL-737R (Carbone and Kohn 1999), respectively. BLAST analysis revealed that the ITS (ON545758), CAL (OP886852), and TEF1-α (OP886853) sequences were 100% (527/527 base pairs), 99.21% (504/508 base pairs), and 99.41% (336/338 base pairs) similar to the strain FAU636 of D. sojae (KJ590718, KJ612115, KJ590761), respectively. Phylogenetic analysis based on concatenated sequences of ITS, TEF1-α, and CAL using MEGA 7.0 by maximum likelihood attributed the isolate LMKY12 to the D. sojae clade. Pathogenicity tests were performed on blueberry cv. O'Neal using detached stems (n=8) in laboratory, one-year-old potted plants (n=4) in greenhouse. Inoculations were done by placing mycelial plugs (7 mm in diameter) taken from a 7-day-old PDA culture on wounded stems. Inoculations with uncolonized agar plugs served as negative controls. Reddish dark brown lesions similar to the symptoms were observed on all inoculated stems 7 days after inoculation. No symptoms developed on control stems. Reisolations were successfully made from all the inoculated stems, and the pathogen was confirmed by the presence of pycnidia, alpha conidia and beta conidia. To our knowledge, this is the first report of D. sojae causing blueberry stem canker in China.

First report of stem blight caused by Diaporthe eres on highbush blueberry (Vaccinium corymbosum) in Michigan.

The U.S. is the world's leading producer of highbush blueberries (Vaccinium corymbosum L.), and Michigan is ranked in the top five production states (USDA NASS, 2022). In June and July of 2021, 268 blueberry stem blight samples were collected for a pathogen survey across 22 total fields in Van Buren and Ottawa counties in Michigan. Current season stems with symptoms of necrosis and wilting were collected. Stems were cut just below the necrotic area and cross-sections (2-3 mm long) were surface disinfested in 10% bleach for 1 min, rinsed twice in sterile distilled water, and dried on sterile paper towels. Stem cross-sections were plated onto potato dextrose agar (PDA) amended with 100 µg/ml streptomycin sulfate and 50 µg/ml ampicillin. Plates were incubated at 21°C under a 12-h photoperiod for 5-6 days. Outgrowing fungi with morphology similar to Diaporthe spp. were transferred to new PDA plates 2 consecutive times after 7 days of similar incubation to ensure single colony isolation. After 7 days, colonies consisted of white and light brown mycelia that were mostly flat, with some isolates that had partially raised mycelia towards the center of the plate. After 3-4 weeks, colonies turned brown and gray and produced dark brown pycnidia. Aseptate, hyaline, fusiform to ellipsoid, biguttulate alpha conidia measuring 5.4 to 7.6 x 2.6 to 3.7 µm (n = 60) were produced. No beta conidia were observed. In total, 3 isolates, representing 3 different farms (37-95 km apart) and cultivars ('Duke', 'Jersey', and 'Bluecrop'), as well as 2 counties, were identified as Diaporthe through colony morphology (Gomes et al. 2013, Udayanga et al. 2014). Amplification and subsequent Sanger sequencing were performed for the internal transcribed spacer (ITS) region and portions of the translation elongation factor (TEF) 1-α, β-tubulin (TUB), and histone H3 (HIS) genes using primers ITS5/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999), T1/Bt-2b (Glass and Donaldson 1995), and CYLH3F/H3-1b (Glass and Donaldson 1995), respectively. Representative sequences were deposited in NCBI GenBank (accession no. OQ507870-OQ507872 for ITS, and OQ550272-OQ550278 for TEF, HIS, and TUB). BLASTn results revealed 97-100% identity for all 4 genes across other established D. eres isolates reported in Gomes et al. (2013). For example, JMK047 had 99.8% (577/578 bp), 99.7% (327/328 bp), 100% (701/701 bp), and 100% (439/439 bp) homology with ITS, TEF, TUB, and HIS sequences, respectively, of D. eres CBS 439.82 (accession no. KC343090, KC343816, KC344058, KC343574). Koch's Postulates were fulfilled via pathogenicity tests on 2-year-old potted 'Blueray' plants with 2 isolates. Stems were surface sterilized with 1% bleach then 8-mm long pieces of bark were removed using a sterile razor blade to expose the cambium. Plugs of sterile PDA (negative control) or mycelia from 7-day old cultures on PDA (5-mm diameter) were placed onto the cambium layer and sealed with Parafilm. Six stems on unique plants were inoculated per treatment. Plants were grown in a 20.5°C greenhouse with a 14-hr photoperiod. After 3 weeks, the stems inoculated with D. eres isolates showed similar stem blight symptoms to those observed in the field while control stems remained healthy. Re-isolation and sequencing of the ITS region of 3 replicates per treatment with the protocol described above confirmed symptoms correlated with D. eres isolates. This is the first report of D. eres associated with stem blight of highbush blueberry in Michigan, and the second report in the U.S. (Lombard et al. 2014). Increasing prevalence of D. eres in U.S. blueberries may affect disease management programs. References Carbone, I., and Kohn, L. M. 1999. Mycologia 91:553. 10.1080/00275514.1999.12061051. Glass, N. L., and Donaldson, G. C. 1995. Appl. Environ. Microbiol. 61:1323. 10.1128/aem.61.4.1323-1330.1995. Gomes, R. R., et al. 2013. Persoonia 31:1. 10.3767/003158513x666844. Lombard, L., et al. 2014. Phytopathol. Mediterr. 51(2):287. 10.14601/Phytopathol_Mediterr-14034. Udayanga, D., Castlebury, L. A., Rossman, A. Y., Chukeatirote, E., and Hyde, K. D. 2014. Fungal Divers. 67:203-229. 10.1007/s13225-014-0297-2. USDA NASS. 2022. Noncitrus Fruits and Nuts 2021 Summary. White, T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, Inc., San Diego, California, USA.

Identification and distribution of species of Neofusicoccum that cause blueberry stem blight in Chile

ABSTRACT Stem blight is a destructive woody disease of blueberry (Vaccinium corymbosum) caused by several species of the family Botryosphaeriaceae. A field survey was conducted in the mayor blueberry production area of Chile, comprising latitudes 32°49ʹS to 40°55ʹS, to determine the occurrence and distribution of Botryosphaeriaceae in the region. Together, a multilocus analysis, morphological characterization, and phytopathogenicity testing were used to identify 51 Neofusicoccum isolates belonging to N. nonquaesitum (28 strains), N. parvum (22 strains), and N. australe (1 strain). Of these, N. parvum and N. nonquaesitum were the most commonly found, with N. parvum most frequent from latitude 37°40ʹS to the north and N. nonquaesitum predominantly located from the same latitude toward the south. Morphological traits of the isolates were consistent with the species identified by molecular techniques, despite the overlapping of conidial size of some isolates among species. Pathogenicity trials showed that the three species were pathogenic to blueberry plants and revealed that N. parvum and N. nonquaesitum were the most aggressive species, although variability in virulence was observed among isolates of N. parvum and N. nonquaesitum.

High Efficiency Regeneration System from Blueberry Leaves and Stems.

The main propagation approach is tissue culture in blueberries, and tissue culture is an effective and low-cost method with higher economic efficiency in blueberries. However, there is a lack of stable and efficient production systems of industrialization of tissue culture in blueberries. In this study, the high-efficiency tissue culture and rapid propagation technology system were established based on blueberry leaves and stems. The optimal medium for callus induction was WPM (woody plant medium) containing 2.0 mg/L Forchlorfenuron (CPPU), 0.2 mg/L 2-isopentenyladenine (2-ip) with a 97% callus induction rate and a callus differentiation rate of 71% by using blueberry leaves as explants. The optimal secondary culture of the leaf callus medium was WPM containing 3.0 mg/L CPPU with an increment coefficient of 24%. The optimal bud growth medium was WPM containing 1.0 mg/L CPPU, 0.4 mg/L 2-ip, with which the growth of the bud was better, stronger and faster. The optimal rooting medium was 1/2 Murashige and Skoog (1/2MS) medium containing 2.0 mg/L naphthylacetic acid (NAA), with which the rooting rate was 90% with shorter rooting time and more adventitious root. In addition, we established a regeneration system based on blueberry stems. The optimal preculture medium in blueberry stem explants was MS medium containing 2-(N-morpholino) ethanesulfonic acid (MES) containing 0.2 mg/L indole-3-acetic acid (IAA), 0.1 mg/L CPPU, 100 mg/L NaCl, with which the germination rate of the bud was 93%. The optimal medium for fast plant growth was MS medium containing MES containing 0.4 mg/L zeatin (ZT), 1 mg/L putrescine, 1 mg/L spermidine, 1 mg/L spermidine, which had a good growth state and growth rate. The optimal cultivation for plantlet growth was MS medium containing MES containing 0.5 mg/L isopentene adenine, with which the plantlet was strong. The optimal rooting medium for the stem was 1/2MS medium containing 2.0 mg/L NAA, with which the rooting rate was 93% with a short time and more adventitious root. In conclusion, we found that stem explants had higher regeneration efficiency for a stable and efficient production system of industrialization of tissue culture. This study provides theoretical guidance and technical support in precision breeding and standardization and industrialization in the blueberry industry.

Blueberry stem extract and stem active components prevent blue light-emitting diode light-induced retinal photoreceptor cell damage in vitro.

Blue light causes retinal damage that can lead to ocular diseases such as age-related macular degeneration. In this study, we determined the protective effect of blueberry stem extract (BStEx) and active components on blue light-emitting diode (LED) light-induced retinal photoreceptor cell damage in vitro. Photoreceptor cells cultured in the presence of BStEx or components were exposed to blue light to induce cell damage. BStEx, fractions of BStEx containing proanthocyanidins, chlorogenic acid, catechin, and epicatechin prevented the cell damage and/or inhibited the generation of reactive oxygen species (ROS). Furthermore, BStEx reduced apoptosis and cell death, and inhibited the phosphorylation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase leading to cellular apoptosis induced by blue light exposure. These findings suggest that BStEx and components exert a protective effect against blue light-induced photoreceptor cell damage through the inhibition of MAPK phosphorylation and ROS production.

Blueberry Stem Extract Prevents Lacrimal Hyposecretion in Non-obese Diabetic Mice via Activation of AMPK.

Tears secreted from the lacrimal gland are essential for preserving the ocular surface. Thus, dysfunction of the lacrimal gland in Sjögren's syndrome (SS) can lead to dry eye, resulting in a reduced quality of life. We previously reported that blueberry 'leaf' water extract prevents lacrimal hyposecretion in male non-obese diabetic (NOD) mice in a SS-like model. In this study, we investigated the effect of blueberry 'stem' water extract (BStEx) on lacrimal hyposecretion in NOD mice. Male NOD mice were fed 1% BStEx or control (AIN-93G) for 2, 4, or 6 weeks from 4 weeks of age. Pilocarpine-induced tear secretion was measured using a phenol red-impregnated thread. The lacrimal glands were histologically evaluated by HE staining. Inflammatory cytokine levels in the lacrimal glands were measured using ELISA. Immunostaining was performed to examine aquaporin 5 (AQP5) localization. The expression levels of autophagy-related proteins, AQP5, and phosphorylated AMPK were measured using western blotting. After feeding BStEx to mice for 4 or 6 weeks, tear volume was observed to have increased in the BStEx group compared with that in the control group. There were no significant differences in inflammatory cell infiltration, autophagy-related protein expression, or the localization and expression of AQP5 in the lacrimal glands between the two groups. In contrast, AMPK phosphorylation increased in the BStEx group. BStEx prevented lacrimal hyposecretion in the SS-like model of male NOD mice, probably by opening tight junctions via the activation of AMPK in lacrimal acinar cells.

Neofusicoccum vaccinii: A Novel Species Causing Stem Blight and Dieback of Blueberries in China.

Blueberries (Vaccinium spp.) have been considered to be a superfood because of their health benefits. Stem blight or dieback of blueberry has been frequently observed in commercial plantations, with incidences between 15 and 30% being observed in China. The causal agents of blueberry stem blight and dieback were surveyed at four commercial blueberry plantations in the Shandong, Fujian, Guizhou, and Yunnan Provinces of China during 2017 and 2019. Twenty-eight isolates of Neofusicoccum were obtained from 75 diseased and dead stem samples. Two taxa were identified. Of these, one novel species, Neofusicoccum vaccinii, was identified based on morphological characteristics and DNA sequence analysis of the concatenated internal transcribed spacer, the translation elongation factor-1α gene, and the beta-tubulin gene. Koch's postulates tests indicated that N. vaccinii was pathogenic toward blueberry. N. parvum is the other species isolated in this study. The optimal temperature for mycelial growth was 30°C for both N. vaccinii and N. parvum. N. vaccinii, however, was more virulent than N. parvum in this study at temperatures ranging from 25 to 30°C. Coinoculation of N. vaccinii and N. parvum did not lead to increased disease severity. On the contrary, the aggressiveness of N. vaccinii was suppressed by the presence of N. parvum at 25 to 35°C.

An observational investigation of potential cow wheat (Melampyrum lineare Desr.) interference with wild blueberry (Vaccinium angustifolium Ait)

Wild blueberry stem density, length, diameter, biomass, and berries per stem were 28%, 30%, 26%, 61%, and 55% lower in quadrats containing wild blueberry and cow wheat relative to quadrats containing only wild blueberry. Cow wheat may reduce wild blueberry growth and controlled studies to explore this interference are warranted.

Blueberry and blackberry are tolerant to repeated indaziflam applications

AbstractNumerous perennial horticultural crops are grown across the southeastern United States. Blueberry and blackberry (also known as caneberry) are commonly found in roadside stands, promote agritourism via pick-your-own markets, are important for fresh market commercial production in the region, and when processed, provide desirable value added products. Season-long weed control using residual herbicides is crucial for these perennial fruit crops to maximize berry quality and yield. Studies performed from 2012 to 2014 in Lanier and Clinch counties in Georgia evaluated the effects of repeated applications of indaziflam at 35, 75, or 145 g ai ha−1 applied biannually in March and September (five total applications) on growth of ‘Alapaha’ rabbiteye and ‘Palmetto’ highbush blueberry, and ‘Apache’ thornless blackberry. All indaziflam treatments were mixed with glufosinate, and a glufosinate-only treatment was included as a check. Minor leaf chlorosis (<10%) was noted within 30 d after application for all blueberries for all treatments, but this was always transient. Blueberry stem diameter was not different for any treatment, even when indaziflam was applied up to 725 g ai ha−1 over 3 yr as compared to glufosinate alone. There was no chlorosis or stem diameter differences for blackberry noted for any treatment. Indaziflam applied in blueberry and blackberry production provides season-long control of numerous troublesome weed species, without causing injury or negatively impacting crop growth.

Efficacy of Foliar Applied Insecticides for Control of Blueberry Stem Gall Wasp, 2020

Efficacy of Foliar Applied Insecticides for Control of Blueberry Stem Gall Wasp, 2020

Efficacy of Systemic Insecticides for Control of Blueberry Stem Gall Wasp, 2019

Efficacy of Systemic Insecticides for Control of Blueberry Stem Gall Wasp, 2019

Effect of a supplement containing blueberry stem extract in dogs with reduced kidney function

Effect of a supplement containing blueberry stem extract in dogs with reduced kidney function

Efficacy of Foliar Applied Insecticides for Control of Blueberry Stem Gall Wasp, 2019

Efficacy of Foliar Applied Insecticides for Control of Blueberry Stem Gall Wasp, 2019

Botryosphaeriaceae species associated with blueberry stem blight and dieback in the Centre Region of Portugal

Blueberry (Vaccinium corymbosum) cultivation in Portugal has been growing considerably in the last decade, making it a highly profitable fruit crop. Species of Botryosphaeriaceae are relevant pathogens of blueberry causing stem blight and dieback. In this study a survey was carried out in blueberry orchards in the centre region of Portugal in order to assess which species of Botryosphaeriaceae are associated with stem blight and dieback symptoms. Their presence as endophytes was also evaluated in asymptomatic plants. Four species were identified, Botryosphaeria dothidea, Neofusicoccum parvum, N. australe and N. eucalyptorum. Of these, B. dothidea and N. parvum were the most commonly found. Pathogenicity trials showed that the four species tested were pathogenic to blueberry plants and revealed that N. parvum, was the most aggressive species, and most likely the main causal agent of blueberry stem blight and dieback in Portugal. Neofusicoccum eucalyptorum, a common Eucalyptus pathogen, is reported for the first time as a pathogen of blueberry. This represents a significant host jump whose potential future effects on blueberry plantations are not fully understood.

Stem Blight of Blueberry Caused by Lasiodiplodia vaccinii sp. nov. in China.

Blueberries (Vaccinium spp.) are largely cultivated in China because of their nutritional benefits and economic value. Blueberry stem blight caused by members of the Botryosphaeriaceae has become one of the most severe diseases affecting blueberry cultivation in China. In this study, we examined the causal agent of blueberry stem blight at commercial greenhouse farms in the suburban area of Beijing, China. In total, 37 isolates of Botryosphaeriaceae were obtained from 100 stem blight samples of blueberry. Twelve of 37 strains were morphologically consistent with the genus Lasiodiplodia, showing ellipsoid to ovoid, one-celled, hyaline conidia that sometimes turned brown, with median septa and longitudinal striations when mature. These 12 strains were identified as belonging to a novel fungal species, Lasiodiplodia vaccinii, based on phylogenetic analysis of the concatenated internal transcribed spacer, RNA polymerase II gene, β-tubulin gene, and translation elongation factor-1α gene sequences as well as morphological characteristics. Pathogenicity tests indicated that L. vaccinii can cause twig blight on blueberry seedlings in the greenhouse. Mycelial growth of L. vaccinii occurred at pH values ranging from 3.0 to 10.0, with an optimum at 6.2, and at temperatures from 15 to 40°C, with an optimum at 30.3°C. Of the seven carbon sources tested, sucrose, fructose, and glucose were all highly efficient in supporting the mycelial growth of L. vaccinii, and xylose was the least effective. Of six nitrogen sources tested, yeast extract and tryptone best promoted mycelial growth of L. vaccinii. The ability of L. vaccinii to grow at high temperatures may help to explain its occurrence in Beijing greenhouses in this study.

Macrophominavaccinii sp. nov. causing blueberry stem blight in China.

Blueberries (Vaccinium spp.) have been widely cultivated in China because of their nutritional benefits and economic value. Blueberry stem blight has become one of the most severe diseases influencing blueberry productivity and quality in China. In this study, eight fungal isolates were obtained from twenty stem blight lesions of blueberry collected in Nanping, Fujian province, China. Asexual stage was observed after inducing sporulation, the morphology of which agrees with Macrophomina in the black, smooth, hard sclerotia and ellipsoid to obovoid, smooth hyaline conidia with apical sheath. Furthermore, DNA sequences of concatenated ITS, tef1-α, TUB, and ACT loci indicated that these isolates belong to a novel fungal species. The distinguishing morphological characteristics, such as the wider conidia and larger conidiomata pycnidial, also support its new status. Thus a novel fungus, Macrophominavaccinii, was described in this study. Pathogenicity tests indicated that M.vaccinii could cause stem blight of blueberry.

Effects of blueberry leaf and stem extracts on hepatic lipid levels in rats consuming a high-sucrose diet

Background: Blueberry stems, a by-product of blueberry leaf tea production, are typically discarded. We evaluated the effects of hot-water extracts of rabbiteye blueberry (Vaccinium virgatum Aiton; RB species) leaves and stems on hepatic lipid levels in rats consuming a high-sucrose diet.Methods: Male Sprague-Dawley rats were divided into groups that received a control high-sucrose diet alone or supplementation with 2.0% blueberry leaf extract or 0.5% or 2.0% blueberry stem extract. Blood and hepatic lipid levels, hepatic lipogenic enzyme activity, and hepatic quercetin metabolites were evaluated after 28 days of ad libitum consumption.Results: Supplementation with the extracts did not affect body weight gain, food intake, liver and white adipose tissue weights, or serum lipid levels. Hepatic triglyceride and total cholesterol levels were reduced in the groups that received 2.0% supplementation of either extract. Hepatic malic enzyme activity was also reduced in those groups. Quercetin and its glycosides, the major polyphenols identified in the extracts, accumulated in the liver as quercetin aglycone and quercetin metabolites. Conclusion: We demonstrated how daily consumption of blueberry leaf and stem extracts can decrease hepatic lipid levels, potentially downregulating malic enzyme activity. These effects were intensive in leaf extracts. The active compounds existed in both extracts may be quercetin and its glycosides. Therefore, blueberry stems and leaves may be an attractive candidate novel functional food.Keywords: Blueberry leaf; blueberry stem; quercetin; hepatic lipid; rat; functional food

Botryosphaeriales associated with stem blight and dieback of blueberry (Vaccinium spp.) in New South Wales and Western Australia

Stem blight and dieback caused by species of the Botryosphaeriales are important diseases of blueberry worldwide. In recent years, stem blight and dieback symptoms have been increasingly observed affecting blueberry production in Australia. Thirty samples were collected from symptomatic plants in an orchard at Corindi NSW, a major blueberry growing region. In addition, samples from symptomatic blueberry plants were submitted by growers to the Plant Health Diagnostic Service, NSW Department of Primary Industries from eight orchards in New South Wales (NSW), and a single orchard in Western Australia (WA). Culture isolations, DNA sequencing and pathogenicity testing were undertaken to determine the species causing the disease. Fifty-two isolates were recovered in total, forty-eight from NSW, and four from WA. A multi-locus sequencing approach was used to assist species identification including the internal transcribed spacer region of rDNA including 5.8S (ITS), partial translation elongation factor 1-alpha (tef1-α), and DNA-directed RNA polymerase II second largest subunit (rpb2). Eight species from three genera were identified; the most common was Neofusicoccum parvum (n = 34), followed by N. kwambonambiense (n = 7), N. occulatum (n = 5), L. theobromae (n = 2), Botryosphaeria dothidea (n = 1), N. australe (n = 1), N. macroclavatum (n = 1) and Lasiodiplodia pseudotheobromae (n = 1). The pathogenicity testing showed all isolates produced lesions on blueberry stems. This study provides the first survey of Botryosphaeriales causing blueberry stem blight and dieback in Australia, and is a valuable resource for plant pathologists and growers trying to manage the disease.