Effects of Latitude and Weather Conditions on Proanthocyanidins in Blackcurrant (Ribes nigrum) of Finnish Commercial Cultivars

Blackcurrants of three Finnish commercial cultivars 'Mortti', 'Ola', and 'Melalahti' cultivated in southern and northern Finland were compared on the basis of the content and composition of proanthocyanidins (PAs). Seventeen B-type PA oligomers (degree of polymerization 2-5 and 7) were detected by hydrophilic interaction liquid chromatography and electrospray ionization mass spectrometry. Total PAs, dimers, trimers, and tetramers were quantified. Among the three cultivars, 'Ola' had the highest contents of both total PAs and PA oligomers. 'Melalahti' was separated from both 'Mortti' and 'Ola' by PA profiles in the partial least-squares discriminant analysis model. All three cultivars revealed distinct responses to latitude and weather conditions. The content of total PAs showed a positive correlation to latitude in 'Ola' and 'Melalahti'. Among the meteorological variables, high temperature and radiation correlated negatively with total PAs, while only specific variables showed a correlation with PA oligomers.

Application of HPLC-PDA-MS metabolite profiling to investigate the effect of growth temperature and day length on blackcurrant fruit

INTRODUCTION

Blackcurrant (Ribes nigrum L.) is an excellent example of a "super fruit" with potential health benefits. Both genotype and cultivation environment are known to affect the chemical composition of blackcurrant, especially ascorbic acid and various phenolic compounds. Environmental conditions, like temperature, solar radiation and precipitation can also have significant impact on fruit chemical composition. The relevance of the study is further accentuated by the predicted and ongoing changes in global climate.

OBJECTIVES

The aim of the present study was to provide new knowledge and a deeper understanding of the effects of post flowering environmental conditions, namely temperature and day length, on fruit quality and chemical composition of blackcurrant using an untargeted high performance liquid chromatography-photo diode array-mass spectrometry (HPLC-PDA-MS) metabolomics approach.

METHODS

A phytotron experiment with cultivation of single-stemmed potted plants of blackcurrant cv. Narve Viking was conducted using constant temperatures of 12, 18 or 24 °C and three different photoperiods (short day, short day with night interruption, and natural summer daylight conditions). Plants were also grown under ambient outdoor conditions. Ripe berries were analysed using an untargeted HPLC-PDA-MS metabolomics approach to detect the presence and concentration of molecules as affected by controlled climatic factors.

RESULTS

The untargeted metabolomics dataset contained a total of 7274 deconvolved retention time-m/z pairs across both electrospray ionisation (ESI) positive and negative polarities, from which 549 metabolites were identified or minimally annotated based upon accurate mass MS. Conventional principal component analysis (PCA) in combination with the Friedman significance test were applied to first identify which metabolites responded to temperature in a linear fashion. Multi-block hierarchical PCA in combination with the Friedman significance test was secondly applied to identify metabolites that were responsive to different day length conditions. Temperature had significant effect on a total of 365 metabolites representing a diverse range of chemical classes. It was observed that ripening of the blackcurrant berries under ambient conditions, compared to controlled conditions, resulted in an increased accumulation of 34 annotated metabolites, mainly anthocyanins and flavonoids. 18 metabolites were found to be regulated differentially under the different daylength conditions. Moreover, based upon the most abundant anthocyanins, a comparison between targeted and untargeted analyses, revealed a close convergence of the two analytical methods. Therefore, the study not just illustrates the value of non-targeted metabolomics approaches with respect to the huge diversity and numbers of significantly changed metabolites detected (and which would be missed by conventional targeted analyses), but also shows the validity of the non-targeted approach with respect to its precision compared to targeted analyses.

CONCLUSIONS

Blackcurrant maturation under controlled ambient conditions revealed a number of insightful relationships between environment and chemical composition of the fruit. A prominent reduction of the most abundant anthocyanins under the highest temperature treatments indicated that blackcurrant berries in general may accumulate lower total anthocyanins in years with extreme hot summer conditions. HPLC-PDA-MS metabolomics is an excellent method for broad analysis of chemical composition of berries rich in phenolic compounds. Moreover, the experiment in controlled phytotron conditions provided additional knowledge concerning plant interactions with the environment.

Profiles of Volatile Compounds in Blackcurrant ( Ribes nigrum) Cultivars with a Special Focus on the Influence of Growth Latitude and Weather Conditions

The volatile profiles of three blackcurrant ( Ribes nigrum L.) cultivars grown in Finland and their responses to growth latitude and weather conditions were studied over an 8 year period by headspace solid-phase microextraction (HS-SPME) followed by gas-chromatographic-mass-spectrometric (GC-MS) analysis. Monoterpene hydrocarbons and oxygenated monoterpenes were the major classes of volatiles. The cultivar 'Melalahti' presented lower contents of volatiles compared with 'Ola' and 'Mortti', which showed very similar compositions. Higher contents of volatiles were found in berries cultivated at the higher latitude (66° 34' N) than in those from the southern location (60° 23' N). Among the meteorological variables, radiation and temperature during the last month before harvest were negatively linked with the volatile content. Storage time had a negative impact on the amount of blackcurrant volatiles.

Metabolic Fingerprinting of Dormant and Active Flower Primordia of Ribes nigrum Using High-Resolution Magic Angle Spinning NMR

Global warming may modify the timing of dormancy release and spring growth of buds of temperate fruit crops. Environmental regulation of the activity-dormancy cycle in perennial plants remains poorly understood at the metabolic level. Especially, the fine-scale metabolic dynamics in the meristematic zone within buds has received little attention. In this work we performed metabolic profiling of intact floral primordia of Ribes nigrum isolated from buds differing in dormancy status using high-resolution magic angle spinning (HR-MAS) NMR. The technique proved useful in monitoring different groups of metabolites, e.g., carbohydrates and amino acids, in floral primordia and allowed metabolic separation of primordia from endo- and ecodormant buds. In addition, due to its nondestructive character, HR-MAS NMR may provide novel insights into cellular compartmentation of individual biomolecules that cannot be obtained using liquid-state NMR. Out results show that HR-MAS NMR may be an important method for metabolomics of intact plant structures.

Analysis and Sensory Evaluation of Volatile Constituents of Fresh Blackcurrant (Ribes nigrum L.) Fruits

Volatile constituents of fresh blackcurrant (Ribes nigrum L.) berries were isolated via vacuum-headspace extraction and analyzed by capillary gas chromatography-mass spectrometry. In agreement with previous studies with frozen fruits, short-chain esters and terpenes were major compound classes. However, rather high concentrations of C₆-compounds (e.g., (E)-hex-2-enal, (Z)-hex-3-enal) constituted a striking difference to data reported for frozen fruits. Frozen storage of blackcurrant berries was shown to result in drastically reduced concentrations of C₆-compounds and a shift of the volatile profile in favor of terpenes. The time-dependent enzymatic formation and isomerization of C₆-compounds adds an additional element of variability to the spectrum of fresh blackcurrant volatiles. Nevertheless, blackcurrant cultivars can be classified according to the major classes of the volatiles of the fresh fruits, if prerequisites, such as the same growing location and the same state of ripeness, are met. The sensory contributions of volatiles of blackcurrant berries were assessed by gas chromatography-olfactometry in combination with aroma extract dilution analysis. 4-Methoxy-2-methyl-2-butanethiol, (Z)-3-hexenal, ethyl butanoate, 1,8-cineole, oct-1-en-3-one, and alkyl-substituted 3-methoxypyrazines were among the volatiles showing the highest aroma activity values.

Species identification, host range and diversity of Cecidophyopsis mites (Acari: Trombidiformes) infesting Ribes in Latvia

Cecidophyopsis mites are important pests in all cultivation regions of Ribes causing bud galls and sterility. Despite their economic importance, the knowledge on Cecidophyopsis species infesting Ribes in various areas of the world is still deficient. The present study was carried out to identify Cecidophyopsis species occurring in Latvia on cultivated and wild Ribes, to assess their host range and gain insight into the genetic diversity of these insufficiently studied pests by use of multiplex PCR, rDNA sequences and morphological characters. Cecidophyopsis alpina, C. aurea, C. spicata and C. selachodon were detected to occur in all surveyed habitats. For the first time, C. alpina was identified on blackcurrants and redcurrants, and C. aurea on redcurrants, blackcurrants and alpine currants. The presence of C. ribis was not confirmed with molecular tools during this study. Phylogenetic analyses confirmed the presence of four Cecidophyopsis species identified by multiplex PCR. A close phylogenetic relatedness was found for C. aurea and C. alpina, and for C. ribis and C. spicata highlighting the necessity for additional studies. Our findings suggest a need to consider also other Cecidophyopsis species besides C. ribis in breeding programs for host resistance to mites.

Influence of Controlled Postflowering Temperature and Daylength on Individual Phenolic Compounds in Four Black Currant Cultivars

The effects of postflowering temperature and daylength on the concentration of individual phenolic compounds were studied in black currant (Ribes nigrum L.) berries under controlled phytotron conditions. The four cultivars studied varied greatly in their concentrations of individual phenolic compounds and temperature stability for accumulation. The concentrations of a wide range of identified phenolic compounds were strongly influenced by temperature over the 12-24 °C range, often with opposite temperature gradient patterns for compounds within the same subclass. Accumulation of anthocyanins and flavonols increased under natural long day conditions, which provided an increased daily light integral, while under identical light energy conditions, photoperiod had little or no effect on the concentration of phenolic compounds. Furthermore, with the exception of members of the hydroxycinnamic acid subclass, the concentration of most phenolic compounds was higher in berries ripened outdoors than in the phytotron, apparently due to screening of UV-B radiation by the glass cover.

Flavonol Glycosides in Currant Leaves and Variation with Growth Season, Growth Location, and Leaf Position

Flavonol glycosides (FG) were analyzed in the leaves of six currant cultivars (Ribes spp.) with HPLC-DAD, HPLC-MS/MS, and NMR. The average amounts of the 12 major, identified FG constituted 86-93% (9.6-14.1 mg/g DW) of the total of 27 FG found. Quercetin and kaempferol were the major aglycones with trace amounts of myricetin. Quercetin-3-O-(2,6-α-dirhamnopyranosyl-β-glucopyranoside), quercetin-3-O-(2-β-xylopyranosyl-6-α-rhamnopyranosyl-β-glucopyranoside), and kaempferol-3-O-(3,6-α-dirhamnopyranosyl-β-glucopyranoside) were identified for the first time in currant leaves and existed in a white currant cultivar 'White Dutch' only. Kaempferol-3-O-β-(6'-malonyl)glucopyranoside was also a new compound existing in abundance in five cultivars but not in the white one. The results show the primary importance of the genetic background of the cultivars. The content of malonylated FG of special importance in cardiovascular health decreased regularly during summer. Time of collection and leaf position were more prominent factors affecting the composition than were the year of harvest or the growth latitude. Randomly collected leaves differed in their FG profiles from those collected from the middle position of new branches.

Berry antioxidants: small fruits providing large benefits

Small berry fruits are consumed because of their attractive colour and special taste, and are considered one of the richest sources of natural antioxidants. Their consumption has been linked to the prevention of some chronic and degenerative diseases. The term 'berry fruits' encompasses the so-called 'soft fruits', primarily strawberry, currants, gooseberry, blackberry, raspberry, blueberry and cranberry. The objective of this review is to highlight the nutraceutical value of berries and to summarize the factors affecting berry fruit antioxidants. Particular attention is given to postharvest and processing operation factors that may affect fruit phytochemical content. The structure-antioxidant relationships for phenolic compounds - the main group of antioxidants in this fruit group - are presented and major areas for future research are identified.

Phenols and ascorbic acid in black currants (Ribes nigrum L.): variation due to genotype, location, and year

Black currant berries contain many biochemical compounds with proven or potential human health benefits. We studied the content of total and single polyphenols, ascorbic acid, soluble sugars, and titratable acidity for two advanced selections and three cultivars of black currant at two distant locations in Sweden (south: 56°06'N; north: 65°21'N) over a 3 year period. Regression analyses revealed the effect of genotype to be considerably larger than that of location and year. However, significant effects of location, year, and interactions were also revealed. A principal component analysis nevertheless separated the genotypes. The content of ascorbic acid, total phenols, total anthocyanins, and soluble sugars was highest in berries from the south, whereas the content of phenolic acids and titratable acidity was highest in berries from the north. The results show that selection of cultivars and production sites are important for cultivation of high-quality black currant raw material for health-promoting products.

Analysis and sensory evaluation of gooseberry (Ribes uva crispa L.) volatiles

Volatiles of gooseberries (Ribes uva cripsa L.) were isolated by means of vacuum-headspace-extraction, and the obtained concentrates were analyzed via capillary gas chromatography-mass spectrometry. To ensure the quantitation of highly volatile compounds, headspace analysis was additionally performed on selected batches. C₆-components (e.g., (Z)-hex-3-enal, (E)-hex-2-enal), derived from lipid oxidation, and short-chain esters (e.g., ethyl acetate, methyl butanoate, ethyl butanoate) turned out to be the major compound classes in the fresh fruit. The compositional variability was demonstrated by analyzing several gooseberry varieties at different stages of ripeness. The contributions of volatiles to the gooseberry aroma were assessed by using gas chromatography-olfactometry in combination with aroma extract dilution analysis and calculation of odor activity values. C₆-components and esters were shown to be responsible for the green and fruity character of fresh gooseberries.

Relationship between polyphenol content and anti-influenza viral effects of berries

BACKGROUND

Berries are known to have many kinds of biological activities. We focused on their antiviral effect, which has not yet been well evaluated.

RESULTS

We compared the anti-influenza viral effects of berries belonging to the genus Vaccinium - 35 species of blueberry (Vaccinium cyanococcus), the Natsuhaze (Vaccinium oldhamii), bilberry (Vaccinium myrtillus) and cranberry (Vaccinium oxycoccos)- with those belonging to the genus Ribes, i.e. blackcurrant (Ribes nigrum). Only Elliott and Legacy among Northern Highbush varieties but many Rabbiteye varieties such as Austin, Baldwin, Brightblue, Festival, T-100 and Tifblue showed anti-influenza viral activity. Natsuhaze, bilberry, cranberry and blackcurrant had high antiviral effects. A relationship was observed between the antiviral effect and total polyphenol content.

CONCLUSIONS

Antiviral effects were found to differ markedly between berry species. Rabbiteye varieties tended to have higher antiviral effects than Northern, Southern and Half Highbush blueberry varieties. We also found that Natsuhaze, which has recently been harvested in Japan as a potential functional food, had an antiviral effect comparable to that of bilberry, cranberry and blackcurrant. There was a positive relationship between antiviral activity and polyphenol content, indicating the possibility that polyphenol is one of the key factors in the antiviral effects of berries.

Effects of latitude and weather conditions on phenolic compounds in currant (Ribes spp.) cultivars

Effects of growth latitude and weather conditions on phenolic compounds of currants (Ribes spp.) were investigated. The berries of red currant cultivar 'Red Dutch', white currant 'White Dutch', and green currant 'Vertti' were collected in seven consecutive years from two growth sites (south and north) with a latitudinal distance of 690 km. The contents of hydroxycinnamic acid conjugates and flavonol glycosides in 'Vertti' were higher than those in 'White Dutch' by 8 and 5 times, respectively, and by 50 and 3 times than those in 'Red Dutch', respectively. The total content of phenolic compounds was 10-19% higher in the north than in the south (p < 0.05). In 'Red Dutch', anthocyanins were 12% richer in berries from the north compared with those from the south (p < 0.05). The total content of hydroxycinnamic acid conjugates in 'Vertti' and 'White Dutch' from the north was 30% higher than those from the south (p < 0.05). High radiation and temperature were associated with low contents of the major phenolic compounds in all the cultivars studied. High humidity correlated with low levels of hydroxycinnamic acid conjugates in green and white currants.

Linking ascorbic acid production in Ribes nigrum with fruit development and changes in sources and sinks

BACKGROUND AND AIMS

Understanding the synthesis of ascorbic acid (l-AsA) in green tissues in model species has advanced considerably; here we focus on its production and accumulation in fruit. In particular, our aim is to understand the links between organs which may be sources of l-AsA (leaves) and those which accumulate it (fruits). The work presented here tests the idea that changes in leaf and fruit number influence the accumulation of l-AsA. The aim was to understand the importance of leaf tissue in the production of l-AsA and to determine how this might provide routes for the manipulation of fruit tissue l-AsA.

METHODS

The experiments used Ribes nigrum (blackcurrant), predominantly in field experiments, where the source-sink relationship was manipulated to alter potential leaf l-AsA production and fruit growth and accumulation of l-AsA. These manipulations included reductions in reproductive capacity, by raceme removal, and the availability of assimilates by leaf removal and branch phloem girdling. Natural variation in fruit growth and fruit abscission is also described as this influences subsequent experimental design and the interpretation of l-AsA data.

KEY RESULTS

Results show that fruit l-AsA concentration is conserved but total yield of l-AsA per plant is dependent on a number of innate factors many of which relate to raceme attributes. Leaf removal and phloem girdling reduced fruit weight, and a combination of both reduced fruit yields further. It appears that around 50 % of assimilates utilized for fruit growth came from apical leaves, while between 20 and 30 % came from raceme leaves, with the remainder from 'storage'.

CONCLUSIONS

Despite being able to manipulate leaf area and therefore assimilate availability and stored carbohydrates, along with fruit yields, rarely were effects on fruit l-AsA concentration seen, indicating fruit l-AsA production in Ribes was not directly coupled to assimilate supply. There was no supporting evidence that l-AsA production occurred predominantly in green leaf tissue followed by its transfer to developing fruits. It is concluded that l-AsA production occurs predominantly in the fruit of Ribes nigrum.

[Biologically active substances of black currant of new varieties]

The assortment of black currant actively replenishes and is constantly updated as a result of successful work of domestic and foreign selectors. New grades of black currant are characterized by the raised content of biologically active substances, including vitamin C, P-active agents, pectin and are of special interest for studying. Fresh berries of seven grades (Azhurnaya, Arapka, Iskushenie, Kreolka, Ladushka, Orel serenade, Ocharovanie) of black currant which were selected by the All-Russian research institute of selection of fruit crops and are perspective for cultivation in the Central Chernozem Region of Russia were chosen as objects for research. The nutritional value of fresh berries was found to vary. Average content of soluble solids was 14.1%, while those below the average were observed in Kreolka (12.1%). The maximum amount of sugars characterized Ladushka grade (11.05%), minimum--Kreolka (9.00%). It has been found that most varieties have fairly high acidity. It is worth noting grade Ladushka, which had the highest sugar-acid index (4.39), with the lowest acidity (2.51%). The highest content of ascorbic acid was found in varieties Orel Serenade--183.7 mg/100 g, the smallest--Ocharovanie--110 mg/100 g, grade Azhurnaya, Kreolka, Ladushka exceeded this indicator average value (144.9 mg/100 g). In terms of the amount of P-active substances stood grades having values above the average (722.2 mg/100 g): Azhurnaya (789.8 mg/100 g), Kreolka (864.5 mg/100 g), Oryol serenade (765.6 mg/100 g). The average content of pectin in the studied berries of black currant was 7.92%, with a minimum of 6.30% was observed in grades Azhurnaya, maximum 9.90%--the kind Oryol serenade. High values of this index were characterized by grade Ladushka, Ocharovanie. Azhurnaya varieties, Creole, Orel serenade had high levels of ascorbic acid and P-active substances. Sort Ladushka marked as a dessert due to the largest sugar-acid ratio. Ladushka, Orel Serenade, Ocharovanie have the highest pectin content. This determine the usefulness of new varieties of blackcurrant as fresh, as well as for production of functional foods.

An approach to the determination of winter chill requirements for different Ribes cultivars

Winter chilling is critical for flowering and fruiting of many temperate fruits, with evidence that blackcurrant (Ribes nigrum L.) cropping has been adversely affected by warm winters. Accurate models of chill accumulation in blackcurrant are required so that breeding strategies can be formulated for the generation of new cultivars with resilience to future climates. Existing models for chill accumulation have largely been derived from statistical correlation; here we report the derivation of improved models for blackcurrant using controlled environment treatments. Hardwood cuttings from a diverse set of cultivars were exposed to constant or varying chilling temperatures and the effects on bud break after transfer to a warm, permissive environment evaluated. The impact of different combinations of temperature and chilling periods were described in terms of their overall 'Effectiveness' (E). Clear genotypic differences were found, with excessive chilling often inhibiting bud break. There was a significant interaction between observed chilling response and the period of low temperature exposure. A number of chilling models to explain observed interactions between chilling temperature and time of exposure on bud break were compared; the most effective involved an optimal response to increasing chill accumulation. The effects of varying temperatures during chilling on bud break were complex, with warm temperature breaks substantially inhibiting bud development and cooler temperature breaks tending to enhance bud burst. The relevance of these models to generic studies of endodormancy is discussed, together with their potential application to the development of phenotyping screens for future breeding using diverse blackcurrant germplasm.

Compositional differences of phenolic compounds between black currant (Ribes nigrum L.) cultivars and their response to latitude and weather conditions

Phenolic compounds in black currants of three Finnish cultivars and their response to growth latitude and weather conditions were analyzed over a six-year period. 'Melalahti' had lower contents of total phenolic compounds (31.4% and 29.2% lower than 'Mortti' and 'Ola', respectively), total anthocyanins (32.6% and 30.5%), and total hydroxycinnamic acid derivatives (23.1% and 23.8%) (p < 0.05) and was less affected by growth latitude and weather conditions than 'Mortti' and 'Ola'. However, all the cultivars grown at higher latitude (66°34' N) had lower contents of total flavonols, total anthocyanins, and total phenolic compounds than those grown at lower latitude (60°23' N) (p < 0.05). The content of total hydroxycinnamic acid conjugates did not vary in 'Melalahti' (p > 0.05) but increased as the latitude increased in 'Mortti' and 'Ola' (p < 0.05). Temperature and radiation were the major weather variables influencing the composition of phenolic compounds. Delphinidin-3-O-glucoside, delphinidin-3-O-rutinoside, and myricetin-3-O-glucoside content showed positive correlations with temperature and radiation in all three cultivars. The study gives important guidelines for the selection of raw materials and growth sites as well as for the berry cultivation for commercial exploitation of black currant berries.

The influence of early yield on the accumulation of major taste and health-related compounds in black and red currant cultivars (Ribes spp.)

The focus of our study was to investigate the effect of crop load on the accumulation and composition of primary metabolites (sugars and organic acids), selected groups of flavonoids (anthocyanins and flavonols), and total phenolics in two subsequent years in four black currant cultivars ('Titania', 'Triton', 'Tsema', and 'Cacanska crna') and three red currant cultivars ('Junifer', 'Rolan', and 'Stanza'). For the determination and quantification of compounds, high-performance liquid chromatography-photodiode array with a mass spectrometer was used. Significant differences among cultivars were detected in all analyzed compounds. Anthocyanins were the predominant phenolic group and were more abundant in black currant cultivars as compared to red ones. Similar amounts of sugars and organic acids were measured in both Ribes species; however, vitamin C was 3-fold higher in black currants. A larger crop load in the second year had a negative effect on the sugar content of berries and promoted a higher degree of acids, with the exception of vitamin C, which was higher in the year with a lower crop load. On the other hand, the content of anthocyanins and flavonols was higher in the year with a larger crop load, while there were no differences in total phenolic content.

Interchangeable effects of gibberellic acid and temperature on embryo growth, seed germination and epicotyl emergence in Ribes multiflorum ssp. sandalioticum (Grossulariaceae)

Morphophysiological dormancy was investigated in seeds of Ribes multiflorum Kit ex Roem et Schult. ssp. sandalioticum Arrigoni, a rare mountain species endemic to Sardinia (Italy). There were no differences in imbibition rates between intact and scarified seeds, suggesting a lack of physical dormancy, while methylene blue solution (0.5%) highlighted a preferential pathway for solution entrance through the raphe. Embryos were small at seed dispersal, with an initial embryo:seed ratio (E:S) of ca. 0.2 (embryo length, ca. 0.5 mm), whereas the critical E:S ratio for germination was three times longer (ca. 0.6). Gibberellic acid (GA(3), 250 mg · l(-1)) and warm stratification (25 °C for 3 months) followed by low temperature (<15 °C) enhanced embryo growth rate (maximum of ca. 0.04 mm · day(-1) at 10 °C) and subsequent seed germination (radicle emergence; ca. 80% at 10 °C). Low germination occurred at warmer temperatures, and cold stratification (5 °C for 3 months) induced secondary dormancy. After radicle emergence, epicotyl emergence was delayed for ca. 2 months for seeds from three different populations. Mean time of epicotyl emergence was affected by GA(3) . Seeds of this species showed non-deep simple (root) - non-deep simple (epicotyl) morphophysiological dormancy, highlighting a high synchronisation with Mediterranean seasonality in all the investigated populations.

Candidate genes associated with bud dormancy release in blackcurrant (Ribes nigrum L.)

BACKGROUND

The detrimental effects of mild winter temperatures on the consistency of cropping of blackcurrant (Ribes nigrum L.) in parts of Europe have led to increasing interest in the genetic control of dormancy release in this species. This study examined patterns of gene expression in leaf buds of blackcurrant to identify key differential changes in these profiles around the time of budbreak.

RESULTS

Using leaf bud tissue of blackcurrant, a cDNA library was generated as a source of blackcurrant ESTs for construction of a custom microarray, which was used to identify differential gene expression during dormancy release. Gene activity was lowest in early stages of dormancy, increasing to reach a maximum around the time of budbreak. Genes with significantly changing expression profiles were clustered and evidence is provided for the transient activity of genes previously associated with dormancy processes in other species. Expression profiling identified candidate genes which were mapped onto a blackcurrant genetic linkage map containing budbreak-related QTL. Three genes, which putatively encode calmodulin-binding protein, beta tubulin and acetyl CoA carboxylase respectively, were found to co-localise with budbreak QTL.

CONCLUSIONS

This study provides insight into the genetic control of dormancy transition in blackcurrant, identifying key changes in gene expression around budbreak. Genetic mapping of ESTs enabled the identification of genes which co-localise with previously-characterised blackcurrant QTL, and it is concluded that these genes have probable roles in release of dormancy and can therefore provide a basis for the development of genetic markers for future breeding deployment.

Direct cryopreservation of winter buds of nine cultivars of blackcurrant (Ribes nigrum L)

Direct cryopreservation of overwintering, dormant buds has been applied to nine blackcurrant cultivars, using a 7 day dehydration period at c.-20° C before plunging directly into liquid nitrogen. The buds on shoots thawed from -20° C showed normal development simply by standing them in water and all the cultivars could be successfully recovered (> 58%) by grafting. None of the shoots thawed from liquid nitrogen showed any development after standing in water and all of the grafts failed. Shoots thawed from liquid nitrogen showed significant damage to xylem transport, and the cortical tissues necessary fro successful grafting showed significant loss of membrane semipermeability. However, buds excised from shoots immediately after thawing from liquid nitrogen were viable and could be recovered using in vitro culture. Survival ranged from 88 to 55%, depending upon cultivar.

High-performance liquid chromatography analysis of black currant (Ribes nigrum L.) fruit phenolics grown either conventionally or organically

Black currants (Ribes nigrum L.) contain a diverse range of phenolics and possess a high antioxidant activity, which makes them an interesting target for the functional food industry. In this study, phenolic profiles of organically and conventionally grown black currant fruits, collected from commercial farms within a climatically similar area, were compared. Compounds were identified using UV/vis and mass spectroscopy techniques and quantified with high-performance liquid chromatography equipped with UV/vis detection. Several different conjugates of hydroxycinnamic acids, flavonols, and anthocyanins were quantified. Statistically significant differences between farms were found for almost all compounds. Differences between the highest and the lowest measured values of major phenolic compounds of different phenolic classes ranged from 24 to 77%. Principal component analysis quite effectively separated farms from each other but did not cluster them according to cultivation technique. Thus, it was concluded that the biochemical quality of organically grown black currant fruits does not differ from those grown conventionally.

Antioxidant capacity of black currant varies with organ, season, and cultivar

Small berries such as black currant constitute one of the important sources of potential health-promoting phytochemicals because these fruits are rich sources of compounds with high antioxidant properties. In this work, antioxidant capacities of different parts (buds, leaves, fruits) of various black currant cultivars were compared throughout the growing season with the aim to prepare extracts with high antioxidant capacity. Buds (opened, at the end of March) and leaves (in June) had a higher content in phenolics and antioxidants than fully ripened berries (in July) and the best yield (per branch) was obtained with the leaves collected in June due to their higher biomass. The differences observed among the eight cultivars tested were small. Concerning flavonols, quercetin was dominant in all organs and cultivars, myricetin varied widely among the cultivars, and kampferol was very low.

Phosphoenolpyruvate carboxykinase and its potential role in the catabolism of organic acids in the flesh of soft fruit during ripening

Previous studies of grapes and tomatoes have shown that the abundance of phosphoenolpyruvate carboxykinase (PEPCK) increases in their flesh at the start of ripening, and that this coincides with a decrease in its citrate and/or malate content. Thus, PEPCK might function in the catabolism of organic acid anions during the ripening of these fruits. In the present study, the abundance of PEPCK was determined in the flesh of blueberries, raspberries, red currants, and strawberries at different stages of their development. In addition, changes in the amounts of citrate, malate, soluble sugars, isocitrate lyase, NADP-malic enzyme, phosphoenolpyruvate carboxylase, and pyruvate, orthophosphate dikinase in the flesh were determined. PEPCK was not detected in strawberry flesh, in which there was no dissimilation of malate or citrate. In the flesh of the other fruits, the abundance of PEPCK increased during ripening to an amount that was similar to that in grapes and tomatoes. In the flesh of blueberries and red currants, PEPCK was most abundant when there was dissimilation of malate. In the flesh of raspberries, PEPCK was most abundant when there was dissimilation of malate and citrate. These results are consistent with PEPCK playing a role in the dissimilation of citrate and/or malate in the flesh of these fruits during ripening. However, PEPCK was also present in the flesh of blueberries, raspberries, and red currants when there was no dissimilation of malate or citrate, and this raises the possibility that PEPCK might have additional functions. Dissection of blueberries provided evidence that both PEPCK and phosphoenolpyruvate carboxylase were present in the same cells, and possible functions for this are discussed.