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.

Altered regulation of TERMINAL FLOWER 1 causes the unique vernalisation response in an arctic woodland strawberry accession.

Vernalisation requirement is an agriculturally important trait that postpones the development of cold-sensitive floral organs until the spring. The family Rosaceae includes many agriculturally important fruit and berry crops that suffer from crop losses caused by frost injury to overwintering flower buds. Recently, a vernalisation-requiring accession of the Rosaceae model woodland strawberry (Fragaria vesca) has been identified in northern Norway. Understanding the molecular basis of the vernalisation requirement in this accession would advance the development of strawberry cultivars better adapted to temperate climate. We use gene silencing, gene expression analysis, genetic mapping and population genomics to study the genetic basis of the vernalisation requirement in woodland strawberry. Our results indicate that the woodland strawberry vernalisation requirement is endemic to northern Norwegian population, and mapping data suggest the orthologue of TERMINAL FLOWER1 (FvTFL1) as the causal floral repressor. We demonstrate that exceptionally low temperatures are needed to downregulate FvTFL1 and to make these plants competent to induce flowering at low postvernalisation temperatures in the spring. We show that altered regulation of FvTFL1 in the northern Norwegian woodland strawberry accession postpones flower induction until the spring, allowing plants to avoid winter injuries of flower buds that commonly occur in temperate regions.

Ascorbate pool, sugars and organic acids in black currant (Ribes nigrum L.) berries are strongly influenced by genotype and post-flowering temperature.

BACKGROUND: Marked effects of the climatic environment on fruit chemical composition have often been demonstrated in field experiments. However, complex covariations of several climatic factors in the natural environment complicate the interpretation of such experiments and the identification of the causal factors. This can be better achieved in a phytotron where the various climatic factors can be varied systematically. Therefore, we grew four black currant cultivars of contrasting origin in a phytotron under controlled post-flowering temperature and photoperiod conditions and analysed the berries for their ascorbic acid, sugar and organic acid contents. RESULTS: The analyses revealed significant effects of genotype on all investigated compounds. Particularly large cultivar differences were observed in the concentrations of l-ascorbic acid (AA) and sucrose. The concentrations of both AA and dehydroascorbic acid (DHAA), as well as the concentrations of all major sugars, decreased consistently with an increasing temperature over the temperature range 12-24 °C. Fructose and glucose were the predominant sugars with concentrations several fold higher than that for sucrose. AA was the main contributor to the total ascorbate pool in black currant berries. The AA/DHAA ratio varied from 5.6 to 10.3 among the studied cultivars. The concentration of citric acid, which was the predominant organic acid in black currant berries, increased with an increasing temperature, whereas the opposite trend was observed for malic and shikimic acid. Quninic acid was always present at relatively low concentrations. By contrast, photoperiod had no significant effect on berry content of any of the investigated compounds. CONCLUSION: It is concluded that the post-flowering temperature has marked effects on the concentration of important chemical compounds responsible for taste and nutritional value of black currant berries, whereas photoperiod has no such effect in the studied cultivars. © 2016 Society of Chemical Industry.

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.

Temperature rather than photoperiod controls growth cessation and dormancy in Sorbus species.

Environmental regulation of growth and dormancy of four Sorbus genotypes was studied in controlled environments. Emphasis was placed on assessment of the presence and nature of the deficient photoperiodic dormancy regulation system that has previously been reported for some woody Rosaceae species. Two genotypes of Sorbus aucuparia L. maintained indeterminate growth for 8 weeks and 9 weeks at temperatures of 15 °C and 21 °C in both 20 h and 10 h photoperiods, while at 9 °C, in the same photoperiodic conditions, they immediately ceased growing. At the higher temperatures, initiation of new leaves (nodes) was unaffected by photoperiod, while internode elongation was significantly enhanced by long days (LD). However, even after prolonged exposure to 9 °C, most plants resumed growth when moved to high temperature and LD, indicating a shallow state of dormancy. Seedlings of Sorbus intermedia (J. F. Ehrh.) Pers. and micro-propagated plantlets of S. commixta Hedl. 'Dodong' were also unaffected by photoperiod during primary growth, but failed to elongate and gradually became dormant regardless of temperature and day-length conditions. However, after chilling and breaking of dormancy, the plants elongated vigorously but changed to a determinate mode of growth. Furthermore, a temperature of 9 °C was found to be fully effective for breaking dormancy in S. intermedia plants. It is concluded that deficient photoperiodic dormancy control seems widespread in the Rosaceae and that, in such plants, both dormancy induction and release is brought about by low temperature. The potential impacts of climate change on such trees are discussed.

Influence of postflowering temperature on fruit size and chemical composition of Glen Ample raspberry (Rubus idaeus L.).

The effects of postflowering temperature on the fruit chemical composition of Glen Ample raspberries were studied under controlled environment conditions. The berry weight decreased significantly with increasing temperature (12, 18, and 24 °C) and with progress of the harvest period. Because the moisture content increased in parallel with the berry weight, the antioxidant capacity (AOC) and the concentration of a range of bioactive compounds decreased with decreasing temperature and progress of the harvest season when expressed on a fresh weight basis in the conventional way. Under those circumstances, dry weight units are therefore preferable. However, despite the dilution effect of large berries, the concentration of ascorbic acid (vitamin C) increased with decreasing temperature, even on a fresh weight basis. Berry AOC was closely correlated with total phenolic concentration (r = 0.958), predominantly anthocyanins and ellagitannins. While a total of 10 anthocyanins were detected, cyanidin-3-sophoroside and cyanidin-3-(2(G)-glucosylrutinoside)-rutinoside accounted for 73% of the total, the former decreasing and the latter increasing with increasing growth temperature. By far, the most prevalent ellagitannins were lambertianin C and sanguiin H-6, both of which increased significantly with increasing temperature. It is concluded that the growth temperature has significant and contrasting effects on the concentration of a range of potentially bioactive compounds in raspberry.

Dual induction rather than intermediate daylength response of flowering in Echinacea purpurea.

Echinacea purpurea cv. Bravado and Magnus have been reported to be intermediate daylength plants (IDP) which flower in response to photoperiods between 13 and 16 h. The present experiments with E. purpurea cv. Bravado show that E. purpurea is actually a dual induction short-long-day plant which flowers promptly and consistently when grown in short day (SD) followed by long day (LD) conditions, but not with the reverse sequence of photoperiods. The flowering response increased with increasing duration of both the SD and the LD treatments. A minimum of 4 weeks of SD followed by 12 LD was required for complete flowering. No flowering occurred in continuous SD or LD, whereas a high proportion of plants flowered in continuous 14-h daylength. However, flowering was more variable in intermediate daylength than after transition from SD to LD. Furthermore, photoperiods between 13 and 16 h could satisfy both the primary SD induction and the secondary LD induction requirements. As a number of dual induction plants, both short-long-day and long-short-day plants, have such an overlapping window of effective photoperiods that can trigger both the SD and LD responses, the rationale for maintaining IDP as a separate and genuine flowering response group is seriously challenged.