Northern Highbush Blueberry Cultivars Research Articles

Sensitivity of Northern Highbush Blueberry Cultivars to Soil Water Deficits during Various Stages of Fruit Development

In many regions, water limitations are increasing because of frequent and persistent droughts and competition for water resources. As a result, growers in these regions, including those producing blueberries, must limit irrigation during drier years. To identify the most critical periods for irrigation, we evaluated the effects of soil water deficits during various stages of fruit development on different cultivars of northern highbush blueberry (Vaccinium corymbosum L.). The study was conducted for 2 years in western Oregon and included two early season cultivars, ‘Earliblue’ and ‘Duke’, a midseason cultivar, ‘Bluecrop’, and two late-season cultivars, ‘Elliott’ and ‘Aurora’. Volumetric soil water content and stem water potentials declined within 1 to 2 weeks with no rain or irrigation in each cultivar and were lowest during the later stages of fruit development. Water deficits reduced berry weight by 10% to 15% in ‘Earliblue’ and ‘Elliott’ when irrigation was withheld in the second year during early or late stages of fruit development and by 6% to 9% in ‘Aurora’ when irrigation was withheld in either year during the final stages of fruit development. However, water deficits only reduced yield significantly in ‘Aurora’, which produced 0.8 to 0.9 kg/plant fewer fruit per year when irrigation was withheld during fruit coloring. In many cases, water deficits also reduced fruit firmness and increased the concentration of soluble solids in the berries, but they had inconsistent effects on titratable acidity and sugar-to-acid ratios. As a rule, water deficits were most detrimental during later stages of fruit development, particularly in midseason and late-season cultivars, which ripened in July and August during the warmest and driest months of the year.

Modeling the Effect of Different Medium on Rooting of Northern Highbush Blueberry (Vaccinium corymbosum L.) Softwood Cuttings

This study was to develop a mathematical modeling to prediction for the effects of different mediums on degree and percentage of rooting of highbush blueberry (Vaccinium corymbosum L.) softwood cuttings. The well fitted estimating equations for the rooting percentage and rooting degree tested were formulized as RP = (95.49533) + (-17.7671 x M)+(1.655312 x M²) + (-24.0961 x CV) and RD = 7.013245 + (-1.29063xM) + (0.119114xM²) + (-1.51642xCV) where RD is rooting degree, RP is rooting percentage, M is mediums, CV is northern highbush blueberry cultivars (Jersey [1] and Berkeley [2]) and M is mediums of the produced equation. Mediums are peat moss (PM) [1], perlite (P) [2], podzolic-brownish soil (BS) [3], podzolic-reddish soil (PR) [4], PM+P [5], PM+BP+PR [6], P+BP+PR [7] and PM+P+BP+PR [8]. All the medium mixed in equal v/v. Here the numerical count put in the angular brackets show the numerical values used for rooting medium and cultivars. Regression analysis over multiply was carried out for the least sum of square (R²) obtained. R2 value 0.92 for percentage of rooting and 0.93 for degree of rooting. Standard errors significances found at the p\0.001 level.

Correlation between fruit size and picking scar size in some organically grown highbush blueberries (Vaccinium corymbosum L.)

This study was carried out to determine the correlation between fruit size and picking scar diameter of organically grown northern highbush blueberry cultivars. In the experiment, eight northern highbush blueberry cultivars (Toro, Brigitta, Darrow, Patriot, Bluecrop, Bluegold, Bluejay and Chandler) (Vaccinium corymbosum L.), have five years old plants and grows in Trabzon conditions, were used. The differences in the fruit size and the picking scar diameter among the cultivars, and the annual differences within each cultivar were studied. Berry width varied between 14.22 - 20.43 mm and fruit weight varied between 1.76 - 4.22 g. While Chandler (2.86 - 3.14 mm) had the biggest scar size, Patriot and Brigitta (2.14 - 2.21 mm) had the smallest scar size. Also, it was determined that picking scar size correlates with fruit width and weight for the harvest year. However, relationship between the fruit width and the scar size of eight cultivars is significantly positive.

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

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

Floral Morphology Differs Among New Northern Highbush Blueberry Cultivars

Variation in floral morphology and timing of bloom are common among cultivars of northern highbush blueberry (Vaccinium corymbosum L.). These differences can affect the ability of commercial pollinators to effectively pollinate and fertilize ovules, which can impact fruit set, berry size, and ultimate yields. New northern highbush blueberry cultivars may exhibit differences in flower morphology, which could impact pollination and fruit set. Evaluation of new cultivars compared to standard industry cultivars is of specific importance in predicting potential pollination constraints by honey bee (Apis mellifera), one of the primary pollinators in North America, and in developing optimal hive stocking densities. Three new cultivars (‘Blue Ribbon’, ‘Top Shelf’, and ‘Cargo’) were compared to an industry standard (‘Duke’) for floral morphology and relative bloom phenology. All new cultivars had significantly smaller flowers as compared to ‘Duke’; however, ‘Top Shelf’ flowers exhibited a unique characteristic whereby many flowers (81%) had partially fused petals. Reduced flower size of new cultivars suggests floral morphology may be a constraint to effective pollination by honey bees and/or these cultivars will require higher honey bee stocking densities for effective pollination. However, the partially unfused petals in ‘Top Shelf’ may provide improved exposure to the stamen and pistil, which could increase accessibility to pollinators like honey bee and promote pollination and fruit set.

Northern Highbush Blueberry Cultivars Differed in Yield and Fruit Quality in Two Organic Production Systems from Planting to Maturity

Northern highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated from planting (Oct. 2006) through 2014 in a certified organic research site in Aurora, OR. The treatments included cultivar (Duke, Bluecrop, Reka, Bluejay, Bluegold, Draper, Legacy, Liberty, Ozarkblue, and Aurora), amendment-mulch [“compost + sawdust” (included preplant amendment and a surface mulch of either an agricultural on-farm crop waste compost or yard-debris compost and sawdust), and “weed mat” (no preplant amendments but with a sawdust mulch topped with weed mat)]. Adding on-farm compost as a preplant amendment and as part of the mulching program increased soil pH from 4.9 to 6.9, organic matter content (OM), and calcium (Ca), magnesium (Mg), and potassium (K) levels compared with the weed mat treatment. The reduced plant growth and yield in some cultivars grown in the compost + sawdust treatment was likely due to the higher soil pH. ‘Bluegold’ and ‘Draper’ were among the cultivars with consistently high flower bud set (40% to 57%), whereas others had consistently low values (e.g., 22% to 45% in ‘Bluecrop’). The number of flowers per bud was affected only by cultivar. There was no effect of year or amendment-mulch treatment on percent fruit set which averaged 93% during the study; however, ‘Ozarkblue’ had a significantly lower fruit set (88%) than only ‘Aurora’ (96%). Berry weight was affected by year (plant age), cultivar, and amendment-mulch treatment. ‘Ozarkblue’ produced the largest berries. Type of amendment-mulch had little effect on berry weight, except in ‘Ozarkblue’, ‘Aurora’, and ‘Reka’ where plants grown with weed mat produced larger fruit than those grown with compost + sawdust. On average, ‘Bluejay’, ‘Draper’, and ‘Liberty’ fruit had the highest percent soluble solids (TSS) and ‘Ozarkblue’ the lowest. Fruit harvested from plants grown with weed mat were firmer than when compost + sawdust was used. ‘Draper’ fruit were much firmer than those of the other cultivars in all years of the study. The number of flower buds per plant multiplied by the number of flowers/bud and berry weight (cultivar specific) and average fruit set was a good predictor of yield in young plants. Yield per plant increased from the second through seventh growing seasons as plants matured in all cultivars except for ‘Duke’ which had the greatest yield in 2014. Cumulative yield was highest in ‘Legacy’ and lowest in ‘Bluejay’ and in ‘Draper’, which had relatively low yield when plants were young. Most cultivars had greater yield when grown with weed mat, whereas ‘Bluegold’ and ‘Liberty’ were unaffected by amendment-mulch treatment. Because weeds were managed in all plots, the cultivar response to amendment-mulch was likely a reflection of sensitivity to preplant amendment with on-farm compost and the resulting higher soil pH. It is possible that the cultivars differed in their adaptability to the various fertility regimes caused by the amendment-mulch treatments and fertilizers used in our study.

Effects of Prior Freezing Conditions on the Quality of Blueberries in a Freeze-Drying Process

Abstract. Freeze-drying has played an increasingly important role in the production of dehydrated foods. This article discusses the operating conditions of the prior freezing process of blueberry fruit to maintain the fruit aroma during the sublimation process. The properties of frozen fruit, such as ice crystal size, seem to depend on the freezing speed, leading to some aroma loss during the sublimation process. The temperature of the deep freezer was set at -20°C, -40°C, -60°C, or -80°C to determine the effects of changing the freezing speed of blueberries during prior freezing. Northern highbush blueberry cultivars Dixi and Elliott harvested in a university orchard (Tokyo, Japan) were used as the test material. The sublimation process of freeze-drying was done using a transparent vacuum desiccator connected to a vacuum pump through a vapor cooling trap under heating conditions provided by a far-infrared heater. Trapped vapors were analyzed with GC-MS to identify and quantify the aroma compounds of the blueberries, such as benzaldehyde. The change in the appearance of the freeze-dried blueberries following prior freezing at various speeds is also described. The amounts of typical volatile compounds, such as acetic acid, 2-hexanol, and 3-hexanol, decreased as the freezing speed increased. Most volatile aroma compounds could be preserved when blueberries were frozen rapidly in a deep freezer. Keywords: Aroma loss, Blueberry, Freeze drying, Freezing speed, Prior freezing.

Changes in berry quality of northern highbush blueberry(Vaccinium corymbosum L.) during the harvest season

As blueberries ripen successively and are commercially harvested over a period of several weeks, their composition may be altered during the harvest. The aim of this study was to compare blueberry fruit composition during the entire harvest season. Fully ripe fruits of two northern highbush blueberry cultivars (Bluecrop and Jersey) were harvested weekly at two different locations. Additionally, the Earliblue cultivar was monitored at a single location. Most of the examined characteristics changed during the harvest season and were cultivar-dependent, with smaller differences observed between sampling locations. Fruit weight of all cultivars decreased with the time of harvest. Levels of total sugars generally increased and total organic acids decreased, making the berries sweeter at the end of the growing period. Moreover, berries harvested later in the season generally contained more total anthocyanins. Total phenolic content generally decreased with successive harvests, mostly due to decreasing contents of total hydroxycinnamic acid derivatives and flavonol glycosides. The results indicate that blueberries harvested at later periods are smaller and contain comparable or increased levels of selected metabolites than larger fruits collected at the beginning of the harvest season.

Heat tolerance of highbush blueberry is related to the antioxidative enzymes and oxidative protein-repairing enzymes

Improving the understanding of the heat-tolerance mechanisms in blueberries (Vaccinium spp.) and screening high heat-tolerant germplasms are critical for the development of this fruit. In the present study, the heat tolerances of the ‘Jersey’ and ‘Diana’ cultivars were compared, which represent the northern and southern highbush blueberry cultivars, respectively. The results showed that exposure to high temperature significantly increased the level of oxidative damage in both highbush blueberries. However, oxidative stress induced by high temperature is significantly lower in ‘Jersey’ than that observed in ‘Diana’. The lower level of oxidative stress in ‘Jersey’ was related to the significantly higher transcript levels of the antioxidative genes and oxidative protein-repairing genes, which may have resulted in the relatively higher semi-lethal high temperature of ‘Jersey’ (48.30°C) than that of the heat-sensitive ‘Diana’(47.32°C). The heat susceptibility of ‘Diana’ was also confirmed by the 3-year field trial, the total death rates of ‘Jersey’ and ‘Diana’ were 7.78 and 12.22%, respectively. Therefore, it can be suggested that some northern highbush blueberry cultivars such as ‘Jersey’ are more heat tolerant than some southern highbush cultivars, and thus suitable for cultivation in lower latitude areas with hot summers.

Seasonal Variation in Leaf Nutrient Concentration of Northern Highbush Blueberry Cultivars Grown in Conventional and Organic Production Systems

Northern highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated for leaf and fruit nutrient concentration at two production sites in 2013–14. The treatments included cultivar (Duke, Bluecrop, Draper, Legacy, Liberty, and Aurora), site [“conventional” (conventionally managed, grower-collaborator site) and “organic” (certified organic research site)], and amendment–mulch [at the organic site only; “organic mulch” (included preplant amendment and a surface mulch of yard debris compost and sawdust); and “weed mat” (no preplant amendments but with a sawdust mulch topped with weed mat)]. Leaf samples were collected every 2 weeks in all treatment plots from late April through early October of each year. Ripe fruit were subsampled from the second harvest for each cultivar. Fruiting season varied from 22 June to 19 Sept. and the highest yielding cultivar, Legacy, had 114% to 330% greater yield than the lowest, Duke, depending on year and site. Cultivar had a significant effect on all fruit nutrients except for phosphorus (P) at the conventional site. Nitrogen (N) and potassium (K) accounted for the largest proportion of nutrient content in the fruit, with 10 to 52 kg·ha–1 and 7 to 34 kg·ha–1 removed in the harvested fruit, respectively, depending on cultivar and site. Fruit carbon concentration ranged from 32% to 44% dry weight with 0.5 to 3.2 t·ha–1 removed in harvested fruit. There were significant year, site, and cultivar effects on leaf nutrient concentrations on many sample dates throughout the season. Despite relatively large differences in management between sites and yield and fruiting season among cultivars, the pattern in leaf nutrient concentration over sampling time was relatively similar between sites and years. Leaf manganese (Mn) and aluminum (Al) concentrations were higher when plants were grown with weed mat as compared with the organic mulch treatment, because soil pH was lower under weed mat than in the organic mulch treatment. ‘Liberty’ had the highest leaf N throughout much of the season at the conventional site. There were relatively large differences among cultivars in leaf magnesium (Mg), calcium (Ca), and K when sampling from mid-July to autumn at both sites. ‘Duke’ and ‘Bluecrop’ tended to have the highest leaf K during this period, whereas ‘Legacy’ and ‘Liberty’ had the lowest. There were greater differences in leaf Ca among cultivars at the conventional site than at the organic site. ‘Draper’ and ‘Legacy’ had higher leaf Ca than ‘Duke’. Leaf nutrient concentrations were within the current published sufficiency levels on many sample dates throughout the season for P, Mg, sulfur (S), Mn, and zinc (Zn), on many dates in midseason for K and Ca, and from mid- to late-season for boron (B) and iron (Fe). However, only when sampled in late July to early August, the current recommended sampling time, was leaf N within sufficiency range. Moreover, there was an effect of cultivar on the concentration of most leaf nutrients at both sites when sampled in late July to early August. The recommended sampling time to determine plant nutrient status in northern highbush blueberry should remain at late July to mid-August, regardless of cultivar, when most nutrients are relatively stable. We recommend lowering the leaf sufficiency range for P and copper (Cu) based on our findings.

Variability of Procyanidin type A- and -B Trimers Content in Aerial Parts of Some Vaccinium Species and Cultivars

Based on the ethnopharmacological data showing that either wild bilberry leaves or whole aerial parts of the plants have been used as antidiabetic drugs, it can be hypothesized that the controversial results of various clinical and animal investigations may be caused by different contents of the active principles in different aerial parts of the bilberry/blueberry (Vaccinium spp.) plants, as well as by their geographical and seasonal variability. The aim of this study was to compare the content of procyanidin type A- and -B trimers in different parts of wild bilberry (Vaccinium myrtillus L.) and northern highbush blueberry (V. corymbosum L.) cultivars. Stems (60 samples) and leaves (30 samples) of wild bilberries and northern highbush blueberry cultivars 'Ama' and 'North Blue' were collected at different locations in Estonia around the year, and analyzed for the concentration of the target polyphenols by HPLC-MS/MS. The highest content of type A doubly linked trimer, a known antidiabetic substance, was established in the stems of V. myrtillus. These contained up to 100 times more of the active substance than the leaves of V. myrtillus and at least 1000 times more than the leaves of V. corymbosum, whereas the seasonal/geographical variation was nearly tenfold. We suggest using stems of V. myrtillus for future animal and clinical investigations of bilberry preparations against diabetes.

Mathematical modeling of the indole-3-butyric acid applications on rooting of northern highbush blueberry (Vaccinium corymbosum L.) softwood-cuttings

The objective of the present study is to develop a mathematical model to predict the effect of indole-3-butyric acid (IBA) on mean rooting (%) and mean root growth of northern highbush blueberry cultivars (Vaccinium corymbosum L.). The best estimating equations for the rooting (%) and root growth are formulized as: RG = (5.672183) + [0.002851 × (IBA)] − [2.0E−6 × (IBA)²] + (−0.27211 × Cv.) and R = (82.00649) + [0.030801 × (IBA)] − [2,4E−5 × (IBA)²] − [2.36218 × (Cv.)] where RG is root growth, R is rooting, IBA is indole-3-butyric acid (ppm) and Cv. is cultivar. Cultivars are Ivanhoe [1], Jersey [2], Rekord [3], Northland [4], Berkeley [5] and Bluejay [6]. The numbers given in square brackets represent the blueberry cultivars for the equations. Multiple regression analysis was carried out until the least sum of squares (R²) was obtained. R2 value 0.90 for rooting and 0.95 for root growth. Standard errors were found to be significant at the p < 0.001 level. The actual rooting differed to the blueberry cultivars and it was between 57.76 and 83.23% while estimated rooting percentage calculated by the produced mathematical model was between 59.04 and 83.80%.

Growth Responses of Three New Zealand Northern Highbush Blueberry Cultivars (Vaccinium corymbosum) to Nutrient Availability.

Responsiveness of three New Zealand northern highbush blueberry cultivars (Vaccinlum corymbosum L.), 'Nui', 'Puru' and 'Reka' to three degrees of regulated nutrient availability was examined: 1) in the control treatment, no nutrient was added, 2) in the solid fertilizer treatment, a standard commercial fertilizer was applied at the start of the experiment, the release of nutrients being dependent on the properties of the fertilizer and environmental conditions, and 3) in the fertigation treatment, a dilute solution of readily available nutrients was supplied daily. Treatments were applied from mid-May 2001 up until plants were destructively harvested in mid-September 2001. For all three cultivars, accumulated dry matter in the fertigation treatment was 2 to 3 times that in the solid fertilizer treatment, whereas that in the control treatment was the least. 'Nui' had the lowest total dry matter levels, they were significantly higher in the fertigation treatment though because of increases in aboveground growth. The root system was unresponsive to the varying nutrient levels applied. 'Reka', the fastest, growing cultivar, had the most responsive root system, its dry weight increasing 2.9 fold in the fertigation compared to the solid fertilizer treatment, that of 'Puru' was intermediate. We concluded that there is potential to apply a finely regulated fertigation system to commercial blueberry production.

`Star' Southern Highbush Blueberry

Southern highbush blueberry cultivars are hybrids bred from a gene pool developed by crossing northern highbush cultivars (largely V. corymbosum L.) with one or more low-chill blueberry species native to the southeastern United States. Vaccinium darrowi Camp has been the most widely used source of climatic adaptation to warm areas. Vaccinium darrowi is a low-growing, late-ripening species with small fruit, and several generations of backcrossing, intercrossing, and selection are normally needed to produce upright-growing cultivars with berries large enough for commercial exploitation. The principal value of southern highbush blueberry cultivars is that they can be cultivated where the mean temperature of the three coldest months is as high as 15 °C, whereas northern highbush blueberry cultivars are not consistently productive where mean temperatures for these months exceed 10 °C. The wide range of northern highbush cultivars and the wide geographic range over which they are cultivated allows fresh fruit harvest from midMay through the end of September in the northern hemisphere and from mid-November through the end of March in the southern hemisphere. The remaining gaps in the harvest year can be filled by growing southern highbush cultivars in areas where temperatures are warm in late winter and early spring. Lowchill southern highbush cultivars are needed in these areas, because climates that are warm enough to promote early berry development in late winter and early spring do not provide sufficient chill units during winter to break dormancy in high-chill cultivars. Southern highbush cultivars can provide fresh blueberries in April and early May in the northern hemisphere and in October and early November in the southern hemisphere. They also make it possible for millions of people living in subtropical and warm-temperate areas to produce blueberries in home gardens or for local markets. ‘Sharpblue’ and ‘Flordablue’, the first southern highbush blueberry cultivars, were released by the Univ. of Florida in 1975 (Sharpe and Sherman, 1976), and other low-chill blueberry cultivars have subsequently been re