Wild Blueberry Research Articles

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.

Response of Plant-Associated Microbiome to Plant Root Colonization by Exogenous Bacterial Endophyte in Perennial Crops.

The application of bacterial inoculums for improving plant growth and production is an important component of sustainable agriculture. However, the efficiency of perennial crop inoculums depends on the ability of the introduced endophytes to exert an impact on the host-plant over an extended period of time. This impact might be evaluated by the response of plant-associated microbiome to the inoculation. In this study, we monitored the effect of a single bacterial strain inoculation on the diversity, structure, and cooperation in plant-associated microbiome over 1-year period. An endophyte (RF67) isolated from Vaccinium angustifolium (wild blueberry) roots and annotated as Rhizobium was used for the inoculation of 1-year-old Lonicera caerulea (Haskap) plants. A significant level of bacterial community perturbation was detected in plant roots after 3 months post-inoculation. About 23% of root-associated community variation was correlated with an application of the inoculant, which was accompanied by increased cooperation between taxa belonging to Proteobacteria and Actinobacteriota phyla and decreased cooperation between Firmicutes in plant roots. Additionally, a decrease in bacterial Shannon diversity and an increase in the relative abundances of Rhizobiaceae and Enterobacteriaceae were detected in the roots of inoculated plants relative to the non-inoculated control. A strong effect of the inoculation on the bacterial cooperation was also detected after 1 year of plant field growth, whereas no differences in bacterial community composition and also alpha and beta diversities were detected between bacterial communities from inoculated and non-inoculated roots. These findings suggest that while exogenous endophytes might have a short-term effect on the root microbiome structure and composition, they can boost cooperation between plant-growth-promoting endophytes, which can exist for the extended period of time providing the host-plant with long-lasting beneficial effects.

Effect of Wild Blueberry Metabolites on Biomarkers of Gastrointestinal and Immune Health In Vitro

Wild blueberries (Vaccinium angustifolium Aiton.) are a rich source of dietary fiber and (poly)phenols with gastrointestinal and immune health-promoting properties, however, their mechanisms of action on the intestinal epithelial cells and transient tissue macrophages remain to be elucidated. In this study, we evaluated the individual effects of anthocyanins, short-chain fatty acids (metabolites derived from fiber), and a series of hydroxycinnamic and hydroxybenzoic acid metabolites common to anthocyanins and other polyphenols on epithelial gut homeostasis in human colon epithelial CCD-18 cells and murine RAW 264.7 macrophages. Gastrointestinal cell migration was enhanced in response to anthocyanin glucosides with the maximum effect observed for malvidin-3-glucoside, and a structural subset of hydroxybenzoic acids, especially 2-hydroxybenzoic acid. Enhanced staining for ZO-1 protein in the junctional complexes was observed in CCD-18 cells treated with malvidin and butyrate, as well as several phenolic metabolites, including hydroxybenzoic and hydroxycinnamic acids. Nitric oxide production and pro-inflammatory gene expression profiles in the LPS-stimulated macrophages were mostly affected by treatments with 3-caffeoylquinic (chlorogenic) and 3,4-dihydroxycinnamic (caffeic) acids, as well as 2-hydroxybenzoic acid. This study lays the foundation for future investigations evaluating the effects of dietary interventions on managing gastrointestinal and inflammatory pathophysiological outcomes.

High Variation in Yield among Wild Blueberry Genotypes: Can Yield Be Predicted by Leaf and Stem Functional Traits?

Wild lowbush blueberry fields are characterized by high genetic diversity, with a large number of genotypes coexisting in every field. Yield also varies among genotypes, which could be related to the variation in physiological and structural traits, but this has not been rigorously tested. In this study, we aimed to quantify the inter-genotype variation in yield, as well as leaf and stem functional traits, and to establish the relationship between functional traits and yield-related traits in wild blueberries. To do so, we carried out a study during the 2019 harvest season measuring structural and functional traits including stem number, stem length, stem diameter, leaf chlorophyll concentration, leaf mass area, leaf area per stem, leaf number per stem, number of branches per stem, leaf temperature, soil temperature, and soil water content and yield data including yield, berry size (weight of 100 berries), number of berries per stem, and length of berry cluster from two wild blueberry farms. We found high variations in structural, functional, and yield-related traits among genotypes, but not between two fields. We also found negative associations of the leaf mass per unit area and midday leaf temperature with the yield, whereas the leaf chlorophyll concentration was positively associated with the yield. Additionally, we found a quadratic relationship between yield-related traits (weight of 100 berries, number of berries per stem, and length of berry cluster) and stem length, with the optimum stem length for yield at 25 cm. Our results suggest that several leaf and stem functional traits are related with yield-related traits; thereby, those traits can be used to predict wild blueberry yields. Our findings could help growers and breeders select better-yielding genotypes based on structural and functional traits.

A HYBRID TECHNIQUE FOR MEASURING THE CONTENT OF XENOBIOTICS IN WILD AND CULTIVATED BLUEBERRIES

Laboratory control requires testing of berry products for the content of residual amounts of mixtures of various xenobiotics: pesticides, polycyclic aromatic hydrocarbons. In this regard, the purpose of this study was to investigate the physicochemical conditions of extraction of xenobiotics from wild and cultivated blueberries and further chromatographic analysis of the obtained extracts. The leading approach to the development of a hybrid method of laboratory control of residual amounts of xenobiotics in berries is the construction of a theoretical model of the method and empirical studies of the proposed conditions of the method. The first stage of the study was sample preparation and extraction of xenobiotics. It was found that pesticides should be extracted from homogenized plant material, and for the extraction of polycyclic aromatic hydrocarbons, berries with an intact skin should be used. It was found that 1% acetonitrile solution of formic acid is a unified extractant of xenobiotics. The need for sequential chromatographic analysis of the obtained extracts by using high-performance liquid chromatography with a fluorescent detector, methods of high-performance liquid chromatography and gas chromatography with mass-selective detectors was substantiated. Approbation measurements showed that the limit of quantitative determination of residual quantities of pesticides is 0.01±0.001 mg/kg, and the limit of quantitative determination of polycyclic aromatic hydrocarbons is much lower and is 0.5±0.05 μg/kg. The hybrid technique allows detecting and measuring the content of xenobiotics in extracts of blueberry berries within 90 minutes. The working ranges for controlling pesticide content are from 1.0 mg/kg to 0.01 mg/kg, for polycyclic aromatic hydrocarbons – from 20 µg/kg to 0.5 µg/kg. The magnitude of the error of the quantitative analysis was estimated using the root-mean-square deviation from the mean (σ, %). The completeness of extraction of xenobiotics was established as a percentage (r, %) using a series of studies of model samples artificially enriched with xenobiotics. It was found that the measurement error of xenobiotic content does not exceed 20%, the value of analyte extraction is within 90-108%, the method is suitable for laboratory control. The developed hybrid method is of practical value for performing laboratory control of chemical compounds dangerous to human health

Managing Botrytis blossom blight of wild blueberry through field sanitation, lime sulfur and Trichoderma application

Botrytis blossom blight is an important disease of wild blueberries (Vaccinium angustifolium) and causes substantial yield loss annually. Field trials that involve primary inoculum reduction and disease reduction techniques were conducted for the 2015/2016 and 2019/2020 growing seasons. The aim of this study was to evaluate the single and combined effects of thermal treatment, calcium polysulphide and Trichoderma harzianum T-22 application on Botrytis blossom blight development, physical plant structure and harvestable yield over the 2-year production cycle of the crop. The treatments were such that fields were thermally treated in May after pruning, followed by calcium polysulphide application in November 2015 and 2019. Trichoderma harzianum was applied in June 2016 and 2020 as single and combined treatments. Thermal treatment + calcium polysulphide + T. harzianum and thermal treatment + calcium polysulphide combinations reduced Botrytis blossom blight incidence and severity by over 50% and 74%, respectively, compared with the untreated control in both seasons. Plots receiving only the thermal treatment and calcium polysulphide as well as the calcium polysulphide + T. harzianum combination showed reductions in disease incidence of over 51, 38 and 81%, and reductions in disease severity of 55, 39 and 68%, respectively, compared with the untreated control. Plots that received thermal treatment combined with calcium polysulphide had taller stems, and a higher number of floral and vegetative buds. Results from this study have demonstrated that Botrytis blossom blight in wild blueberry fields can be adequately reduced when calcium polysulphide is used tandem with thermal treatment and biofungicides.

Are Foliar Fertilizers Beneficial to Growth and Yield of Wild Lowbush Blueberries?

Wild lowbush blueberry is an economically and culturally important crop in North America. Different fertilizer companies have been advertising their foliar fertilizer products to the wild blueberry growers, claiming better growth and production of this crop with no scientific proof. Although foliar fertilization has shown to be efficient for delivering micronutrients in deficit for different crops by reducing soil activation and environmental contamination, limited research has been done in wild blueberries. It is still unknown how foliar fertilizers affect the physiology, growth, and yield of this crop. Therefore, we tested the impacts of seven foliar treatments containing macro- and micro-nutrients and plant hormones (Seacrop16, Salvador, Agro-Phos applied in 2019 and Kali-T, Nano-Gro, Poma, Poma + Nanocellulose applied in 2020) on this crop for one crop cycle from vegetative year (2019) to crop year (2020). We tested these products against the standard soil-applied granular fertilizer called Diammonium phosphate (DAP) and control (no fertilizer) in a randomized complete block design with eight replicates in a conventional wild blueberry field in Maine, USA. In 2019, no significant differences across the applied treatments were observed in crop physiology and growth except in leaf chlorophyll concentration. In 2020, there was significantly higher leaf chlorophyll concentration in SeaCrop16 and Poma+Nanocellulose plots, but significantly lower photosynthetic rates in DAP and SeaCrop16 treated plots compared to the control. Meanwhile, no significant differences in plant height, leaf characteristics, or blueberry yield were found among the treatments. Overall, mobile nutrients (N, P, K) from soil applied fertilizers and foliar fertilizers containing other immobile nutrients (Ca) and/or plant hormones might benefit crop growth, but the impact on yield is limited. We also reveal that the wild blueberry physiological and morphological traits and leaf nutrients in the vegetative year are more related to the crop yield than those traits in the crop year. This implies that a combination of wild blueberry physiology, morphology, and leaf nutrients in the vegetative year largely impact their yield in the following crop year.

Will Climate Warming Alter Biotic Stresses in Wild Lowbush Blueberries?

As global temperatures rise, a growing need exists for understanding the impacts of warming on crop production. Warming not only changes crop physiology and growth but also the weeds, insect pests, and diseases of crops including wild lowbush blueberries, which have not been studied till now. Changes in pest pressures can cause instability in production and will require changes in management practices and the development of mitigation strategies. The objective of this study was to determine the impacts of warming on the prevalence of major weeds, insect pests, and diseases of the wild blueberry production system. We selected six genotypes of wild lowbush blueberries in a commercially managed wild blueberry field in Maine Northeast USA and used open-top-chambers (OTCs) to study the effects of warming for two years (2019 and 2020). Both active-heating OTCs (elevated monthly mean temperatures by 3.3 °C) and passive-heating OTCs (elevated by 1.2 °C) were employed and compared with ambient controls. Our results showed that warming did not change the prevalence of red leaf disease, blueberry gall midge, red-striped fireworm, or any weed species. In contrast, the incidence of Sphaerulina leaf spot, powdery mildew, and other leaf spot disease were significantly lower under warming treatments compared to the ambient control at the end of the growing season in 2020. Overall, different pests responded to warming differently, inviting further research to reveal the mechanisms. The lower overall pressure of leaf spot disease under warming was probably due to decreased air humidity.

Blueberries and health

Blueberry is a high value crop globally. Both wild and cultivated blueberries are commercially available to consumers. Although mostly consumed as fresh or frozen, dried blueberries are also offered in the market. Yogurts, beverages, jams, and jellies made with blueberries are some of the products popular with consumers.Blueberries are rich in several health-beneficial phytochemicals including phenolic compounds and vitamins. This article reviews the health implications of blueberry consumption. The review was limited to the research studies published in peer-reviewed scientific journals. The impact of blueberry intake on cardiovascular functions, obesity, cancer, diabetes, cognitive performance, and gut microbiota was the focus of this review.This review clearly revealed very broad health benefits of blueberry intake. However, it is evident that scientific studies on this topic are scarce. Indeed, there are only a few studies on the health effects of blueberries published in scientific journals. The majority of the investigations on this topic were carried out using animal models or cell cultures. Scarcity and limited size of the clinical studies in this field leave many questions about the effect of blueberry consumption on human health unanswered. Undoubtedly, there is a need for large-scale controlled and randomized clinical and epidemiological studies and meta-analyses of the data from such research. This would allow for an in-depth understanding of the effect of blueberries on health and the biological and metabolic pathways involved in disease mitigation and treatment.Keywords: Blueberry, cancer, cardiovascular health, chemical composition, cognitive performance, diabetes, gut microbiota, obesity, phytochemicals

Phenolic Compound Content and the Antioxidant and Antimicrobial Activity of Wild Blueberries (Vaccinium stenophyllum Steud.) Fruits Extracts during Ripening

The genus Vaccinium contains about 400 species distributed worldwide, but only a few species and varieties have had their phenolic composition and biological activity documented. In this study, phenols, flavonoids, anthocyanins, antioxidant and antimicrobial activity of methanolic extracts of Vaccinium stenophyllum Steud. fruits: 1-totally immature, 2-immature, 3-immature/close to maturity and 4-mature, were determined using UV-Visible spectrometry and HPTLC. The totally immature fruit extract showed the highest content of total phenols (19.153 ± 0.175 mg GAE/g DW), chlorogenic acid (20.867 ± 0.240 mg CAE/g DW), and the highest antioxidant activity by ABTS●+ (196.761 ± 0.641 µM TE/g DW) and DPPH● (146.580 ± 6.466 µM TE/g DW). Immature, immature/close to maturity and mature fruits extracts, exhibited the lowest MIC (9.37 mg/mL) and MBC (18.75 mg/mL) against Escherichia coli, Salmonella choleraesuis, and Shigella flexneri. The mature fruits extract exhibited the highest content of total anthocyanins (0.141 ± 0.004 mg CE/g DW) and cyanidin-3-glucoside (19.230 ± 0.309 mg CGE/g DW). The content of phenols, flavonoids and anthocyanins was higher than that reported for other Vaccinium species. These results showed the relevance of Vaccinium stenophyllum Steud. for breeding purposes to enhance the bioactivity of cultivars, or as a source of natural additives for the food industry, among others.

First Record of Invasive Pest Blueberry Gall Midge, Dasineura oxycoccana (Johnson)1 in Mexico: Molecular and Morphological Confirmation

The blueberry gall midge, Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae), is an important pest of wild and cultivated blueberries, Vaccinium spp. (Ericales: Ericaceae), and causes great loss at infested farms. This is the first report of the occurrence of the pest at a plantation in Mexico. Suspicious larvae and adults were collected from flower and vegetative buds of 12,625 (11.2% of the total) infested blueberry plants, Vaccinium corymbosum L. Specimens were identified based on DNA similarity to known sequences of the mitochondrial COI gene and on traditional morphometric analysis of the species. Interestingly, DNA sequence similarity varied depending upon the origin of known sequences: 98.88-99.84% similarity with D. oxycoccana from V. corymbosum in Canada, Japan, and United Kingdom, <91.04% with specimens from Vaccinium macrocarpon from Canada, and <85.85% with other Dasineura species. In conclusion, both (morphometric and molecular) approaches agreed that all analyzed specimens were D. oxycoccana. Once identified, complete control of the pest was achieved 4 weeks after proper measures were initiated.

Is Drought Increasing in Maine and Hurting Wild Blueberry Production?

A few severe drought events occurred in the Northeast (NE) USA in recent decades and caused significant economic losses, but the temporal pattern of drought incidents and their impacts on agricultural systems have not been well assessed. Here, we analyzed historical changes and patterns of drought using a drought index (standardized precipitation-evapotranspiration index (SPEI)), and assessed drought impacts on remotely sensed vegetation indices (enhanced vegetation index (EVI) and normalized difference vegetation index (NDVI)) and production (yield) of the wild blueberry fields in Maine, USA. We also analyzed the impact of short- and long-term water conditions of the growing season on the wild blueberry vegetation condition and production. No significant changes in the SPEI were found in the past 71 years, despite a significant warming pattern. There was also a significant relationship between the relatively long-term SPEI and the vegetation indices (EVI and NDVI), but not the short-term SPEI (one year). This suggests that the crop vigor of wild blueberries is probably determined by water conditions over a relatively long term. There were also significant relationships between 1-year water conditions (SPEI) and yield for a non-irrigated field, and between 4-year-average SPEI and the yield of all fields in Maine. The vegetation indices (EVI and NDVI) are not good predictors of wild blueberry yield, possibly because wild blueberry yield does not only depend on crop vigor, but also on other important variables such as pollination. We also compared an irrigated and a non-irrigated wild blueberry field at the same location (Deblois, Maine) where we found that irrigation decoupled the relationship between the SPEI and NDVI or EVI.

Evaluation of cameras and image distance for CNN-based weed detection in wild blueberry

Agricultural herbicide application efficiency can be improved using smart sprayers which provide site-specific, rather than broadcast, applications of agrochemicals. The YOLOv3-Tiny convolutional neural network (CNN) was trained to detect two weeds, hair fescue and sheep sorrel, in images captured from wild blueberry fields throughout Nova Scotia, Canada. An evaluation was performed in three commercial wild blueberry fields in Nova Scotia to examine the effects of camera selection and target distance on detection accuracy. A Canon T6 DSLR camera, an LG G6 smartphone, and a Logitech c920 webcam were used to capture RGB images at varying distances from target weeds. Mean F1-scores for each combination of camera and image height were analysed in a 3 × 3 factorial arrangement for hair fescue and a 3 × 2 factorial arrangement for sheep sorrel. Images captured from 0.98 m with the LG G6 and Canon T6 produced F1-scores of up to 0.97 for detection of at least one hair fescue tuft. Images captured with the LG G6 and Canon T6 DSLR from 0.57 m achieved F1-scores of 0.94 and 0.93, respectively, for detection of at least one sheep sorrel plant per image. Sheep sorrel was undetectable in images from the Logitech c920 under 19 of 27 parameter combinations. Future work will involve using the CNN to control herbicide applications with a real-time smart sprayer. Additionally, the CNN will be used in a web-based application to detect target weeds and provide site-specific information to aid management decisions. Using a CNN to detect weeds will create improvements in management techniques, resulting in cost-savings and greater sustainability for the wild blueberry industry.

Elucidation of the molecular responses during the primary infection of wild blueberry phenotypes with Monilinia vaccinii-corymbosi under field conditions

BackgroundMonilinia blight caused by Monilinia vaccinii-corymbosi (Reade) Honey (M.vc) is a major disease of wild blueberry that can result in severe crop losses in the absence of an integrated disease management programme. The fungus causes blight in the emerging floral and vegetative buds, but the degree of susceptibility varies among the different wild blueberry phenotypes, ranging from the highly susceptible V. a. f. nigrum to the moderately susceptible V. angustifolium and the least susceptible V. myrtilloides.ResultsThe present study evaluated the defense responses of these major phenotypes during their primary infection (floral buds) with M.vc. The temporal expression profiles of PR genes (PR3 and PR4) and the flavonoid pathway structural genes (CHS, ANS, ANR, DFR and FLS) were analysed. The PR3 and PR4 gene expression profiles revealed that V. myrtilloides responded to M.vc infection by activating the expression of both PR genes. V. a. f. nigrum, on the other hand, failed to activate these genes, while V. angustifolium, exhibited an intermediate response. Our study with the flavonoid pathway genes indicated variability in activation of the genes during post-infection time points with ANS and ANR in V. myrtilloides, FLS in V. angustifolium and no response observed in V. a. f. nigrum.ConclusionsAltogether, this study highlights that the degree of phenotype susceptibility is associated with the timely activation of host defense responsive genes. Data obtained in this study provided a starting point for a better understanding of the wild blueberry- M. vaccinii-corymbosi pathosystem.

Known and New Emerging Viruses Infecting Blueberry.

Blueberry (Vaccinium spp.) plants are exposed to existing and emerging viruses as a result of expanding acreage of blueberry plantations across the world, primarily in North America. Since blueberry is cultivated in areas where there are wild Vaccinium spp., there is increasing risk of virus movement between wild and cultivated blueberries. This is theoretically possible because viruses can spread from commercial cultivars to native species and vice versa causing the spread of existing and new viruses. The occurrence of these viruses in blueberry can be devastating to the industry considering the cost for cultivation and production of this perennial crop. However, the advent of high-throughput sequencing and bioinformatic sequence analysis have allowed for rapid identification of known and novel viruses in any crop including blueberry, thus facilitating proper intervention in response to serious viral diseases. In this paper, we aim to focus on the current status of known and novel viruses emerging in blueberry worldwide, which may impact the blueberry industry.

Field Capacity and Harvest Efficiency Evaluation of Traditional Small Box and Semi-Automated Bin Handling Systems for Wild Blueberries

Mechanical harvesters with small box and semi-automated bin handling systems are increasingly being used for harvesting wild blueberries in Eastern Canada, and Northeastern, USA. However, their field capacity and performance have not been quantified and compared. Important measures of field capacity and efficiency for a traditional mechanical harvester were compared with a novel semi-automatic bin handling harvester. Data were obtained from on-farm field trials conducted at four sites in Nova Scotia, Canada in 2017 and 2018. Both harvesters had double head configurations, along with other similar engineering configurations: (i) 0.66 m picking reels; (ii) 16 picker bars per head and 65 teeth per bar; (iii) 1.72 m picking width; (iv) 21 rpm head speed; and (v) 0.31 ms−1 ground speed. Each harvester was operated for 120 min and data such as berry harvesting time and box handling time were recorded, with six replications during each year. Statistical methods were used to compare the harvest efficiency of the two mechanical harvesters. Harvest time efficiency was significantly higher for the semi-automatic bin handling technology than for the small box handling technology both in 2017 (p &lt; 0.001), and 2018 (p &lt; 0.001). Weed coverage did not have a significant effect of harvest time in either 2017 (p = 0.694) or 2018 (p = 0.765), though it did significantly affect yield in both 2017 (p = 0.011) and 2018 (p = 0.045). The findings provide useful insights for decision-makers contemplating the choice of harvesting technology to sustain profits from wild blueberry production.

Neuroprotective effect of wild lowbush blueberry (Vaccinium angustifolium) on global cerebral ischemia/reperfusion injury in rats: Downregulation of iNOS/TNF-α and upregulation of miR-146a/miR-21 expression.

This study aims to investigate the neuroprotective effect of wild lowbush blueberry on CIRI in rats. Accordingly, CIRI and reperfusion were induced in rats for 60 min and 24 h, respectively. Then, the mechanisms of the neuroprotective effects of BBE were investigated in the injury through evaluating miR-146a, miR-21, and their targets in a CIRI rat model. After that, the BBE (30, 60, and 120 mg/kg b.wt) was intraperitoneally injected for 14 days, then CIRI was induced by BCCAO for 60 min for ischemic stroke and reperfusion for 24 h. Several parameters including the oxidative stress levels in the hippocampus and serum were measured 24 h after the CIRI. The findings showed that the BBE significantly decreased the levels of malondialdehyde (MDA) and nitric oxide (NO) and increased ferric ion reducing antioxidant power (FRAP) levels in the hippocampus and serum following the stroke. The BBE also maximized the miR-146a and miR-21 expressions and moderated iNOS and TNF-α expressions in the hippocampus. Likewise, the BBE enlarged the CA1 and CA3 domains of the post-stroke pyramidal cell layers of the hippocampus. Overall, the results revealed that BBE had potent neuroprotective efficacy against CIRI via the effective modulation of neuroinflammatory cascades and protected neurons against ischemic death.

Rooting of Wild Blueberry (Vaccinium spp.) Cuttings From the Peruvian Northeast

AbstractThe objective of this study was to evaluate the effect of indole-3-butyric acid (IBA) on the rooting of five wild accessions of blueberry (HCHA-262, HCHA-271, HCHA-283, HCHA-286, and HCHA-290) obtained from natural populations in the province of Chachapoyas (northern Peru). Buds were collected from the middle third of the plant and treated with IBA at concentrations of 0, 1,000, 2,000, and 3,000 mg L−1. The results indicated that of the IBA doses, the 2,000-mg L−1dose achieved the best effects on the rooting percentage and the lengths and numbers of roots and shoots of each accession studied. Accessions HCHA-262 and HCHA-283 showed greater regeneration of new seedlings than the other accessions after 45 days. The rhizogenic capacity of the cuttings varied because of the influences of both the IBA concentration and the genotype of the mother plant.

Parameterization and Calibration of Wild Blueberry Machine Learning Models to Predict Fruit-Set in the Northeast China Bog Blueberry Agroecosystem

Data deficiency prevents the development of reliable machine learning models for many agroecosystems, especially those characterized by a dearth of knowledge derived from field data. However, other similar agroecosystems with extensive data resources can be of use. We propose a new predictive modeling approach based upon the concept of transfer learning to solve the problem of data deficiency in predicting productivity of agroecosystems, where productivity is a nonlinear function of various interacting biotic and abiotic factors. We describe the process of building metamodels (machine learning models built and trained on simulation data) from simulations built for one agroecosystem (US wild blueberry) as the source domain, where the data resource is abundant. Metamodels are evaluated and the best metamodel representing the system dynamics is selected. The best metamodel is re-parameterized and calibrated to another agroecosystem (Northeast China bog blueberry) as the target domain where field collected data are lacking. Experimental results showed that our metamodel developed for wild blueberry achieved 78% accuracy in fruit-set prediction for bog blueberry. To demonstrate its usefulness, we applied this calibrated metamodel to investigate the response of bog blueberry to various weather conditions. We found that an 8% reduction in fruit-set of bog blueberry is likely to happen if weather becomes warmer and wetter as predicted by climate models. In addition, southern and eastern production regions will suffer more severe fruit-set decline than the other growing regions. Predictions also suggest that increasing commercially available honeybee densities to 18 bees/m2/min, or bumble bee densities to 0.6 bees/m2/min, is a viable way to compensate for the predicted 8% climate induced fruit-set decline in the future.

Are Wild Blueberries a Crop with Low Photosynthetic Capacity? Chamber-Size Effects in Measuring Photosynthesis

Wild lowbush blueberries, an important fruit crop native to North America, contribute significantly to the economy of Maine, USA, Atlantic Canada, and Quebec. However, its photosynthetic capacity has not been well-quantified, with only a few studies showing its low photosynthetic rates. Its small leaves make accurate leaf-level photosynthetic measurements difficult and introduce potential uncertainties in using large leaf chambers. Here, we determined the photosynthetic rate for five different wild blueberry genotypes using a big leaf chamber enclosing multiple leaves and a small leaf chamber with a single leaf to test whether using big leaf chambers (branch-level measurements) underestimates the photosynthetic capacity. Photosynthetic rates of wild blueberries were significantly (35–47%) lower when using the big leaf chamber, and they are not a crop with low photosynthetic capacity, which can be as high as 16 μmol m−2 s−1. Additionally, wild blueberry leaves enclosed in the big chamber at different positions of a branch did not differ in chlorophyll content and photosynthetic rate, suggesting that the difference was not caused by variation among leaves but probably due to leaf orientations and self-shading in the big chamber. A significant linear relationship between the photosynthetic rate measured by the small and big leaf chambers suggests that the underestimation in leaf photosynthetic capacity could be corrected. Therefore, chamber-size effects need to be considered in quantifying photosynthetic capacity for small-leaf crops, and our study provided important guidelines for future photosynthesis research. We also established the relationship between the Electron Transport Rate (ETR) and photosynthetic CO2 assimilation for wild blueberries. ETR provides an alternative to quantify photosynthesis, but the correlation coefficient of the relationship (R2 = 0.65) suggests that caution is needed in this case.