Freezing Events within Overwintering Buds of Blackcurrant (Ribes nigrum L.)

Overwintering buds of blackcurrant cultivars 'Ben Lomond' and'Ben More' were examined by differential thermal analysis (DTA).Photographic evidence relates the first (primary) exotherm tothe freezing of water in the basal pith and bud scales. Thenumber of secondary exotherms either matched, or was fewer than,the number of floral racemes within the bud. There is evidencein the structure of the secondary exotherms that the freezingof individual primordia was being recorded.Copyright 1993, 1999Academic Press Differential thermal analysis, freezing injury, buds, Ribes nigrum, blackcurrant     

RAPD fingerprinting of blackcurrant (Ribes nigrum L.) cultivars

Ribes nigrum germplasm was screened for random amplified polymorphic DNA (RAPD) markers. Fiftyfour markers were identified which generated individual fingerprints for each of 21 cultivars. Genetic variation within R. nigrum germplasm, as detected by RAPDs, demonstrated that the genetic basis for improvement of blackcurrant is narrower than would be expected by the analysis of parentage.     

Isolation of RNA from blackcurrant (Ribes nigrum L.) fruit

Extraction of high-quality RNA from blackcurrant fruit has hitherto proved difficult, probably owing to high levels of phenolic and polysaccharide components in the berries. The procedure described here is a modification of one described for grape berries, and yields RNA suitable for in vitro translations, RNA blot analysis, and cDNA library construction.     

Multi-environment QTL mapping in blackcurrant (Ribes nigrum L.) using mixed models

The first genetic linkage map of blackcurrant, published by Brennan et al. (Euphytica 161:19–34, 2008), identified regions where quantitative trait loci (QTLs) for some important traits were located. The analysis was complicated by the fact that the mapping population was found to contain two subgroups, with segregation ratios consistent with these being crossed and selfed offspring. The QTL analysis was based on the trait mean over 3 years and focused on the crossed offspring. Here we proposed a mixed model multi-environment approach for this population. The 3 years are considered as three separate environments, the data from both the selfed and crossed offspring are combined and different residual terms are explored to model the correlation between the years. This permits tests for interactions between the QTLs, the year and the type of offspring (selfed or crossed). This is applied to re-analyse two important traits, anthocyanin concentration and budbreak. Several additional QTLs were identified, some affecting the trait in both the selfed and crossed offspring, others in just one.     

Anthocyanin-rich black currant (Ribes nigrum L.) extract affords chemoprevention against diethylnitrosamine-induced hepatocellular carcinogenesis in rats

Anthocyanins are known to possess potent anticarcinogenic properties against several cancers thus demonstrating potential for cancer prevention. Black currant (Ribes nigrum L., Grossulariaceae) fruits have a high anthocyanin content. This “superfruit” is known to possess various pharmacological effects including alleviation of chronic oxidative stress and inflammation. In contrast to a large volume of literature on the health benefits of black currant, limited evidence on antitumor effects of black currant exists with virtually no data on the prevention of experimental carcinogenesis. In the current study, we have investigated the chemopreventive effects of an anthocyanin-rich black currant skin extract (BCSE) utilizing our well-characterized model of rat liver carcinogenesis. Initiation of hepatocarcinogenesis was done by intraperitoneal injection of diethylnitrosamine (DENA) followed by promotion with phenobarbital. The rats were exposed to dietary BCSE for 4 weeks prior to initiation, and the treatment was continued for 22 consecutive weeks. BCSE dose-dependently decreased the incidence, total number, multiplicity, size and volume of preneoplastic hepatic nodules. The antihepatocarcinogenic effect of BCSE was confirmed by histopathological examination of liver sections. Immunohistochemical analysis of proliferating cell nuclear antigen and DNA fragmentation revealed BCSE-mediated inhibition of abnormal cell proliferation and induction of apoptosis in DENA-induced rat liver tumorigenesis respectively. Mechanistic studies revealed that BCSE-mediated proapototic signal during experimental hepatocarcinogenesis may be propagated via the up-regulation of Bax and down-regulation of Bcl-2 expression at the translational level. These results along with a safety profile of BCSE encourage the development of black currant bioactive constituents as chemopreventive agents for human liver cancer.     

The use of chlorophyll fluorescence in assessment of low temperature hardiness in blackcurrant (Ribes nigrum L.)

The effect of freezing stress on chlorophyll fluorescence was examined in leaves of five genotypes of blackcurrant (Ribes nigrum L.). Minimum fluorescence (F_o), variable fluorescence (F_v) and the time for F_v to decay to half its maximum value (q_1/2) all varied between genotypes. Freezing stress significantly reduced F_o in all genotypes, but the effect of freezing stress on F_v was non-significant. Freezing stress significantly increased q_1/2, but the effect varied significantly between genotypes. The increase in q_1/2 induced by freezing stress was greatest in the cultivar Baldwin and least in the accession Ri-74020-6. The effects of freezing on chlorophyll fluorescence, particularly q_1/2, corresponded to the susceptibility of the genotypes to spring frosts. It is concluded that chlorophyll fluorescence can provide a rapid screening technique for assessing frost hardiness in blackcurrant.     

The use of metabolic profiling in the identification of gall mite (Cecidophyopsis ribis Westw.)-resistant blackcurrant (Ribes nigrum L.) genotypes

The terpenoid fractions of bud extracts from blackcurrant genotypes showing resistance or susceptibility to gall mite (Cecidophyopsis ribis) infestation were examined and compared using gas chromatography. By the use of discriminant analysis, and the application of the derived discriminator to the data, resistance status was correctly predicted in 88% of the genotypes sampled. The use of metabolic profiling provides a useful alternative to lengthy field assessments.     

Exudation from Aphid Stylets during the Period from Dormancy to Bud break in Tilia americana (L.)

Aphid stylet exudation during the period from dormancy to budbreak was studied in Tilia americana by means of detached branchesbrought from the woods into conditions of warmth and extendedphotoperiod. During physiological dormancy little exudationwas obtained. Thereafter until mid-March exudation was morevariable, but its onset accelerated progressively until mid-March,after which persistent exudation could be obtained from allbranches within 2 days. When the buds were removed from onebranch at this time, exudation persisted for only 5 days comparedwith 14 to 21 days for branches with buds. To account for theseresults it is suggested that a hormonal factor is produced bythe buds which results in sieve-tube activation, that the factoris virtually absent during physiological dormancy, and thereafterrequires a few weeks to become fully active. Determinations of sugar concentration, level of exudation, andbud dry weight indicated that exudation was most intense beforethe bud sinks were active and then rapidly falls off. It issuggested that the stylet acts as a sink competing with thenatural sinks for solutes from a limited region of the stem.Other interpretations are also considered.     

Immunostimulatory effects of a polysaccharide-rich substance with antitumor activity isolated from black currant (Ribes nigrum L.)

The fruit juice of black currant was found to contain a polysaccharide-rich substance, which was designated cassis polysaccharide (CAPS), with macrophage-stimulating activity. Especially, its interleukin (IL)-1beta-inducing activity was remarkably high, compared with other fruit juice preparations. CAPS was found to consist of rhamnose, mannose, arabinose, galactose, xylose, and glucose in a molar ratio of 11.3:0.9:54.1:29.8:2.0:1.9. CAPS turned out to be partitioned into a soluble component (CAPS-l.m.) and a precipitable component (CAPS-h.m.) with mean MWs of 80,000 and 600,000 respectively in 45% (v/v) ethanol solution. At least in vitro, CAPS-l.m. rather than CAPS-h.m. appeared to play an important role in macrophage activation. Oral administration of black currant juice and CAPS to Ehrlich carcinoma-bearing mice retarded the growth of the solid tumor by 45% and 51% respectively. CAPS administration had a stimulatory effect on the release of IL-2, IL-10, interferon-gamma, and IL-4 from splenocytes in comparison with PBS treatment in tumor-bearing mice. The IL-4 level was, however, still lower than that exhibited by a group of normal mice. CAPS showed a certain cytotoxicity directly against tumor cells.     

Hormonal Regulation of Lateral Bud (Tiller) Release in Oats (Avena sativa L.)

Stem segments containing a single node and quiescent lateral bud (tiller) were excised from the bases of oat shoots (cv. `Victory') and used to study the effects of plant hormones on release of lateral buds and development of adventitious root primordia. Kinetin (10⁻⁵ and 10⁻⁶ molar) stimulates development of tillers and inhibits development of root primordia, whereas indoleacetic acid (IAA) (10⁻⁵ and 10⁻⁶ molar) causes the reverse effects. Abscisic acid strongly inhibits kinetin-induced tiller bud release and elon-gation and IAA-induced adventitious root development. IAA, in combination with kinetin, also inhibits kinetin-induced bud prophyll (outermost leaf of the axillary bud) elongation. The IAA oxidase cofactor p-coumaric acid stimulates lateral bud release; the auxin transport inhibitor 2,3,5-triiodo-benzoic acid and the antiauxin α (p-chlorophenoxy)-isobutyric acid inhibit IAA-induced adventitious root formation. Gibberellic acid is synergistic with kinetin in the elongation of the bud prophyll. In intact oat plants, tiller release is induced by shoot decapitation, geostimulation, or the emergence of the inflorescence. Results shown support the apical dominance theory, namely, that the cytokinin to auxin ratio plays a decisive role in determining whether tillers are released or adventitious roots develop. They also indicate that abscisic acid and possibly gibberellin may act as modulator hormones in this system.     

Seasonal Changes in the Levels of Free and Bound Abscisic Acid in Blackcurrant (Ribes nigrum) Buds and Beech (Fagus sylvatica) Buds

Free and bound abscisic acid (ABA) levels in blackcurrant andbeech buds have been determined by an extraction procedure involvingseveral thin-layer chromatography purification stages and finalbioassay in the wheat coleoptile straight-growth test. In bothspecies the highest level of free ABA occurs in the autumn atabout the time of onset of winter dormancy. The free ABA contentthen declines throughout the winter months reaching its lowestvalue just before bud burst. These results strengthen the viewthat free ABA plays an important role in the induction and maintenanceof winter dormancy. The bound ABA level increases in both species throughout theautumn and winter until halfway through the bud swelling phaseand then declines. It is proposed that the bound ABA accumulatesin the buds because it cannot be translocated or further metabolizedduring the winter months. The ratios of free to bound ABA were plotted and the resultingcurves show a distinctive annual cycle with the highest freeABA/ bound ABA ratio (F/B) occurring in the autumn and the highestbound ABA/ free ABA ratio (B/F) coinciding with bud burst. Agradual increase in the B/F ratio during bud swelling may indicatea feed-back reaction between free and bound ABA which maintainsthe free ABA at a sufficiently high level to put a gentle brakeon growth. At bud burst the B/F ratio falls very sharply anda period of very rapid growth ensues.     

Estimation of heterozygosity in Ribes nigrum L. using RAPD markers

Heterozygosity in three cultivars of the blackcurrant (Ribes nigrum L.) was estimated. A selfed population of each cultivar was screened for Random Amplified Polymorphic DNA markers (RAPDs) and heterozygous loci were identified by band segregation in contrast with the non-segregation of homozygous loci. On average, 21% of the loci scored in each cultivar were heterozygous. The implications for mapping studies in Ribes nigrum are discussed.     

Anti‐viral and anti‐bacterial activities of an extract of blackcurrants (Ribes nigrum L.)

The inhibitory effects of an extract of the blackcurrant (Ribes nigrum L.) against pathogens associated with oral, nasopharyngeal and upper respiratory infectious diseases; namely respiratory syncytial virus (RSV), influenza virus A and B (IFV‐A and IFV‐B), adenovirus (AdV), herpes simplex virus type 1, Haemophilus influenzae type B, Streptococcus pneumoniae and Streptococcus mutans, were investigated. Less than 1% concentration of extract of blackcurrant inhibited replication of RSV, IFV‐A and ‐B and HSV‐1 by over 50% and a 10% extract inhibited adsorption of these viruses onto the cell surface by over 95%. The effects on AdV were much less pronounced; the half minimal inhibitory concentration of AdV replication was 2.54 ± 0.26, and a 10% concentration of the extract inhibited AdV adsorption on the cell surface by 72.9 ± 3.4%. The antibacterial activities of the blackcurrant were evaluated based on its efficacy as a disinfectant. A 10% extract disinfected 99.8% of H. Influenzae type B and 78.9% of S. pneumoniae in 10 min, but had no demonstrable effect against S. mutans. The blackcurrant extract still showed antiviral and antibacterial activities after the pH had been made neutral with sodium hydroxide, suggesting that these activities are not the result of acidic reactions or of components precipitated at a neutral pH. These findings demonstrate the potential of blackcurrant extract as a functional food for oral care.     

Isobutyl Amides from Pepper (Piper nigrum L.)

Four isobutyl amides were isolated from the fruits of white pepper (Piper nigrum L.) and identified to be N-isobutyl-13-(3,4-methylenedioxyphenyl)-2E,4E,12E-tridecatrienamide (3, guineensine), N-isobutyl-2E,4E,8Z-eicosatrienamide (5), N-isobutyl-2E,4E-octadecadienamide (6) and N-isobutyl-2E,4E-decadienamide (7, pellitorine).     

Dormancy in peach (Prunus persica L.) flower buds

Summary Peach buds (floral and vegetative) were periodically collected from midsummer until the spring flowering and sprouted under continuous light, 100% relative humidity and 20–25°C. Treatments with 200 ppm gibberellin A₃ (GA₃) or chilling (2–4°C for 30 days before planting) were applied. Vegetative buds showed well-defined phenological stages: pre-dormancy, true dormancy, and end of dormancy. Both GA₃ and chilling treatments shortened the sprouting times of vegetative dormant buds close to those in predormancy. Isolated floral buds were irresponsive under all conditions and did not sprout even with the GA₃ or chilling treatments. In a comparative study with buds immediately after collection anatomical analysis demonstrated that vegetative buds were almost completely developed by midsummer/early automn and remained in a resting state until the end of winter. Floral buds developed continuously over the same period. Both types of verticils began to differentiate in midsummer. Sepals and petals developed mainly in late summer, androecious floral parts developed throughout the resting period, while gynoecious floral parts showed differentiation in late winter. The flower was completely formed a few days prior to blossoming. Thus, in isolated peach buds fertile verticils are not sufficiently developed during the resting time to allow sprouting.     

Dormancy in peach (Prunus persica L.) flower buds

Morphological studies were carried out with peach flower buds collected monthly in 1989 and 1990, from two months before leaf fall (7 March) until two to three weeks before bloom (7/8 August). Chilled (2–4°C for 30 days) and unchilled buds were exposed to 20 to 25°C, 100% RH and continuous light. Gibberellin A₃ (3 ng or 30 ng) was applied to some of the non-chilled cuttings at three days intervals. Then, 12, 19, and 26 days after they were planted, the buds were sampled and processed for histological studies. Cultured flower buds (chilled or unchilled) had accelerated anther and gynoecium morphogenesis after 12 days under controlled conditions, compared to buds processed immediately after collection from the field. Chilling treatment augmented the bud culture effect, while Gibberellin A₃ applications to the excised buds retarded bud morphogenesis to a stage comparable to that of buds collected directly from the field. This, suggests that the comparatively high levels of Gibberellin A_1/3 we previously found in mid winter [15, 18] could be at least one of the factors that controls floral bud dormancy by retarding anther and gynoecium development.     

Dormancy studies in black gram (Phaseolus mnngo L.)

Mechanical scarification of seeds ofPhaseolus mungo L. resulted in 100 per cent gormination in comparison to 90 per cent dormant control. Seeds treated with concentrated sulphuric acid for 8 min led to 85 per cent germination. Heat treatment at 70 °C for 24 h exhibited 75 per cent gormination, while boiled water treatment for 7 min caused 65 per cent germination.