Effect of preharvest melatonin applications at dusk on quality and bioactive compounds content of early sweet cherries

BACKGROUND

Early sweet cherries have a high economic impact on cherry growers but have poorer quality characteristics and shorter shelf-life than late cherries. Melatonin has been proposed as a biostimulant that regulates plant and fruit growth and increases fruit quality and shelf-life but, in general in fruit and vegetables, there is controversy about its effects. Therefore, this work aimed to evaluate the impact of exogenous preharvest melatonin applications at dusk on the quality and bioactive compounds of two early sweet cherry cultivars.

RESULTS

The M3 and M5 (3 × 10-4 and 5 × 10-4  mol L-1 melatonin, respectively) treatments effectively enhanced the endogenous melatonin and hydroxycinnamic acid concentration, enhancing the functional properties of the fruit. Additionally, the M5 treatment enhanced skin colour and consumer acceptance of 'Samba' cherries, while the M3 treatment improved cherry size in 'Sandon Rose'.

CONCLUSION

Preharvest melatonin applications at dusk could be included in the scheduled preharvest treatments for early cherry cultivars in order to improve the quality and to stimulate the functionality of the fruit. However, further studies are needed to adjust the concentration depending on the cultivar and the objective pursued. © 2023 Society of Chemical Industry.

Antioxidant Systems and Quality in Sweet Cherries Are Improved by Preharvest GABA Treatments Leading to Delay Postharvest Senescence

γ-Aminobutyric acid (GABA) plays important roles in plant development, including the maintenance of fruit quality when applied as postharvest treatment. However, little information is available about the effects of preharvest GABA treatments. Thus, GABA (10, 50 and 100 mM) was applied as foliar spray at key points of fruit development in three sweet cherry cultivars and over two years. The results show that quality parameters, such as total soluble solid content, titratable acidity and firmness were higher in the fruit from GABA-treated trees than in the controls, either at harvest or during four weeks of cold storage. In addition, the total phenolic and total and individual anthocyanin concentrations were also enhanced by GABA treatments and the fruit color was improved. The activities of the antioxidant enzymes catalase, ascorbate peroxidase and peroxidase were also enhanced by the GABA treatments. The most effective concentration was 50 mM, which led to extending the storage period of sweet cherries with high quality traits to up to four weeks, while for the controls this was two weeks. Thus, GABA treatment had a clear effect on delaying the postharvest ripening and senescence processes in sweet cherries, with an additional effect on enhancing the content of bioactive compounds, such as phenolics and anthocyanins, with antioxidant properties and health benefits.

Valorization of Defatted Cherry Seed Residues from Liquor Processing by Matrix Solid-Phase Dispersion Extraction: A Sustainable Strategy for Production of Phenolic-Rich Extracts with Antioxidant Potential

The integrated valorization of food chain waste is one of the most promising alternatives in the transition to a sustainable bioeconomy. Thus, an efficient solid-phase matrix dispersion extraction method, using experimental factorial design and response surface methodology, has been developed and optimized for the recovery of polyphenols from defatted cherry seeds obtained after cherry liquor manufacture and subsequent fatty acid extraction, evaluating the effect of each processing step on the composition and phenolic content of sweet cherry residues. The phenolic extracts before fermentation showed the highest content of total polyphenols (TPC) and flavonoids (TFC) (3 ± 1 mg QE·g-1 and 1.37 ± 0.08 mg GAE·g-1, respectively), while the highest antioxidant capacity was obtained in the defatted seed extracts after both fermentation and distillation. In addition, high-performance liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (HPLC-ESI-QTOF-MS) was used to determine the phenolic profile. Dihydroxybenzoic acid, neochlorogenic acid, caffeic acid, and quercetin were the main phenolics found, showing differences in concentration between the stages of liquor production. The results underline the prospective of cherry by-products for obtaining phenol-rich bioactive extracts for possible use in different industrial sectors, offering a feasible solution for the cascade valorization of cherry agri-food waste.

Wild sweet cherry, strawberry and bilberry as underestimated sources of natural colorants and bioactive compounds with functional properties

Wild edible fruits, neglected by the development of commercial agriculture, have recently aroused as a good source of natural colorants and bioactive compounds. These novel uses could cover the recent demand for healthier foods with functional properties. Prunus avium, Fragaria vesca and Vaccinium myrtillus wild fruits were characterized by individual anthocyanin profile and color CIELAB parameters, as well as phenolic fraction. In addition, some bioactivities were evaluated. In P. avium cyanidin-O-deoxyhexosyl-pentoside was the representative anthocyanin, in F. vesca pelargonidin-3-O-glucoside and in V. myrtillus delphinidin-O-hexoside. The three wild edible fruits showed interesting antioxidant activity especially in OxHLIA assays. V. myrtillus was the fruit with the best results for the bacterial growth inhibition, while F. vesca with better fungal growth inhibition. These results evidenced the richness of these wild fruits in bioactive compounds and pigments with antioxidant capacity, therefore, their potential use as natural colorants for healthier food products design.

Impact of Pre-Storage Melatonin Application on the Standard, Sensory, and Bioactive Quality of Early Sweet Cherry

Melatonin (N-acetyl-5-methoxytryptamine) is involved in multiple functions in plants. However, its role in some metabolic pathways and exogenous application's effect on fruits is still unclear. Furthermore, the effects of pre-storage melatonin treatment on sensory traits and consumer acceptance of cherries have yet to be studied. For this reason, the early sweet cherry cultivar 'Samba' harvested at the commercial ripening stage was treated with different melatonin concentrations (0.1, 0.3, and 0.5 mmol L^-1) and stored for 21 days under controlled cold temperature and humidity. The standard quality, respiration rate, postharvest aptitude, sensory quality, phenols, and antioxidant systems (non-enzymatic and enzymatic) were analysed at 14 and 21 days of storage. Postharvest treatment with melatonin 0.5 mmol L^-1 improved firmness and reduced weight loss and non-commercial fruit percentage while increasing respiration rate, lipophilic antioxidant activity, and ascorbate peroxidase enzyme activity. Furthermore, the treated cherries showed better sensory qualities, such as uniformity of colour and skin colour, as well as being sourer and showing better consumer acceptance and liking after 14 days of storage. Therefore, we conclude that the 0.5 mmol L^-1 concentration is effective on the standard, sensory, and bioactive quality of early sweet cherries and can be considered an eco-friendly tool for maintaining the postharvest quality of early cherries.

Metabolites That Confirm Induction and Release of Dormancy Phases in Sweet Cherry Buds

Here we report on metabolites found in a targeted profiling of 'Summit' flower buds for nine years, which could be indicators for the timing of endodormancy release (t₁) and beginning of ontogenetic development (t₁*). Investigated metabolites included chrysin, arabonic acid, pentose acid, sucrose, abscisic acid (ABA), and abscisic acid glucose ester (ABA-GE). Chrysin and water content showed an almost parallel course between leaf fall and t₁*. After 'swollen bud', water content raised from ~60 to ~80% at open cluster, while chrysin content decreased and lost its function as an acetylcholinesterase inhibitor. Both parameters can be suitable indicators for t₁*. Arabonic acid showed a clear increase after t₁*. Pentose acid would be a suitable metabolite to identify t₁ and t₁*, but would not allow describing the ecodormancy phase, because of its continuously low value during this time. Sucrose reached a maximum during ecodormancy and showed a significant correlation with air temperature, which confirms its cryoprotective role in this phase. The ABA content showed maximum values during endodormancy and decreased during ecodormancy, reaching 50% of its content t₁ at t₁*. It appears to be the key metabolite to define the ecodormancy phase. The ABA-GE was present at all stages and phases and was much higher than the ABA content and is a readily available storage pool in cherry buds.

Orchard Net Covers Improve Resistance to Cherry Cracking Disorder

Orchard net cover improves plant physiology, yield and fruit quality, pest and disease control, and anticipates fruit ripening. Moreover, this crop technology has been used to reduce natural cherry cracking (NCC). This is a serious physiological disorder that cracks the epidermis, the hypodermis, and the storage parenchyma layers of the fruit due to rainfall events near the harvest and it is related to low fruit osmotic potential and/or high fruit water permeability. This work aims to study the effect of orchard net cover on sweet cherry trees, cv. Early Bigi, in two harvesting years (2019 and 2021). The NCC, the induced cracking index (CI), and the cracking type incidence were determined. In addition, epicuticular and intra-cuticular wax content, biometric and physicochemical parameters were also evaluated. Net cover reduced the natural cracking index by 40%. High fruit weight values were observed in covered trees comparing to the control ones, with increases of 45% and 13%, in 2019 and 2021, respectively. A positive correlation was observed between CI and total soluble solids and a negative correlation between CI and wax content. Therefore, with forecasts of worsening heavy precipitation events near harvest, protecting cherry trees with nets will increase resistance to fruit cracking.

Genetic and Pomological Determination of the Trueness-to-Type of Sweet Cherry Cultivars in the German National Fruit Genebank

Genebank collections preserve many old cultivars with ancient breeding history. However, often, cultivars with synonymous or incorrect names are maintained in multiple collections. Therefore, pomological and genetic characterization is an essential prerequisite for confirming trueness-to-type of cultivars in gene bank collections. In our study, 1442 single sweet cherry (Prunus avium L.) trees of the German Fruit Genebank were evaluated according to their trueness-to-type. For this purpose, pomological analysis was performed, in which the accessions were assigned totheir historical cultivar names. The pomological identifications were based on several historical reference sources, such as fruit references from historical cherry cultivar and fruit-stone collections, as well as historical pomological literature sources. In addition, the cherry trees were genetically analyzed for cultivar identity using 16 SSR markers. Based on pomological characterization and genetic analysis for the majority of the trees (86%), cultivar authenticity could be confirmed. Most markers were highly discriminating and powerful for cultivar identification. The cherry collection showed a high degree of genetic diversity, with an expected heterozygosity He = 0.67. Generally, high genetic admixture between cultivars of different geographic origin and year of origin was obtained after STRUCTURE analysis, demonstrating the extensive exchange of genetic information between cherry cultivars in the collection over time. However, the phylogenetic tree calculated by DARwin reflected the geographic origin of selected cherry cultivars. After parentage analysis with CERVUS, paternity could not be confirmed for three cultivars, indicating the necessity of further pedigree analysis for these cultivars. The results of our study underlined the general importance of evaluating the authenticity of cultivars in genebank collections based on genetic and pomological characterization.

The Phenolic Profile of Sweet Cherry Fruits Influenced by Cultivar/Rootstock Combination

The influence of three cultivars ('Carmen', 'Kordia' and 'Regina') grafted on six rootstocks (Mahaleb, 'Colt', 'Oblacinska', 'M × M 14', 'Gisela 5' and 'Gisela 6') on the phenolic profile of sweet cherry fruits was studied during a two-year period. All the individual phenolic compounds were detected using high-pressure liquid chromatography with diode-array detection coupled with mass spectrometry (HPLC-DAD-MSn). In all the examined samples, 54 compounds were identified and divided into five phenolic classes: anthocyanins (4 compounds), flavonols (7), flavanols (11), flavanones (4), and hydroxycinnamic acids (28). Anthocyanins (58%) and hydroxycinnamic acids (31%) showed the greatest amounts in all the examined fruit samples. PCA analysis revealed that among the cultivars, 'Kordia' showed the highest phenolic content. Regarding rootstocks, the lowest values of the most important phenolic compounds were obtained in fruits from trees grafted onto the seedling rootstock Mahaleb. Among the clonal rootstocks, the vigorous 'Colt' and dwarf 'Gisela 5' promoted the highest values of the evaluated phenolic compounds in the cultivars 'Kordia' and 'Carmen', while the dwarf 'Oblacinska' and semi-vigorous 'M × M 14' induced the highest values in the cultivar 'Regina'. By evaluating the influence of cultivars and rootstocks on the phenolic content in fruit, it has been proven that the cultivar has the most significant influence. However, the rootstock also influences the content of a large number of phenolic compounds. The selection of an adequate cultivar/rootstock combination can also be a powerful tool for improving the phenolic content in fruits, and consequently the nutritional value of sweet cherry fruits.

Comparative evaluation of phenolic profile and antioxidant activity of new sweet cherry (Prunus avium L.) genotypes in Turkey

INTRODUCTION

Sweet cherry (Prunus avium L.), one of the most consumed fruits in the world, is rich in phenolic and especially anthocyanin content.

OBJECTIVE

The aim of this study was to evaluate the phenolic properties of 11 different sweet cherry genotypes collected from Giresun, Turkey.

METHODS

Total phenol, flavonoid, anthocyanin and antioxidant properties were observed spectrophotometrically in three different extraction (conventional, microwave-assisted and ultrasound-assisted) processes. Major phenolic, anthocyanin and antioxidant structures were visually assessed by high-performance thin layer chromatography (HPTLC). Various phenolics in its structure were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

T2 and E5 genotypes had the highest content in terms of total phenol, flavonoid, anthocyanin and antioxidant activity. In HPTLC, cherry samples contained high levels of chlorogenic acid, neochlorogenic acid, p-coumaroylquinic acid, rutin and cyanidin-3 rutinoside. Among the phenolics examined in the LC-MS/MS method, the major compounds in the structure of cherry were found to be chlorogenic acid, rutin and catechin. The T2 genotype had higher phenolics than the other cherry samples (chlorogenic acid 19.3 mg/100 g; catechin; 3.8 mg/100 g; rutin 33.1 mg/100 g).

CONCLUSION

As a result, T2 and E5 genotypes had higher phenolic and antioxidant activity compared to other genotypes and commercial cultivars. It can be said that the antioxidant contents of these genotypes are due to the high anthocyanin amount in their structures. In addition, T2 genotype contained more major phenolics than other cherries. In the next stage, it is recommended to carry out studies on the cultivation of these two varieties.

Detection of Breeding-Relevant Fruit Cracking and Fruit Firmness Quantitative Trait Loci in Sweet Cherry via Pedigree-Based and Genome-Wide Association Approaches

Breeding for decreased fruit cracking incidence and increased fruit firmness in sweet cherry creates an attractive alternative to variable results from cultural management practices. DNA-informed breeding increases its efficiency, yet upstream research is needed to identify the genomic regions associated with the trait variation of a breeding-relevant magnitude, as well as to identify the parental sources of favorable alleles. The objectives of this research were to identify the quantitative trait loci (QTLs) associated with fruit cracking incidence and firmness, estimate the effects of single nucleotide polymorphism (SNP) haplotypes at the detected QTLs, and identify the ancestral source(s) of functional haplotypes. Fruit cracking incidence and firmness were evaluated for multiple years on 259 unselected seedlings representing 22 important breeding parents. Phenotypic data, in conjunction with genome-wide genotypic data from the RosBREED cherry 6K SNP array, were used in the QTL analysis performed via Pedigree-Based Analysis using the FlexQTL™ software, supplemented by a Genome-Wide Association Study using the BLINK software. Haplotype analysis was conducted on the QTLs to identify the functional SNP haplotypes and estimate their phenotypic effects, and the haplotypes were tracked through the pedigree. Four QTLs (two per trait) were consistent across the years and/or both analysis methods and validated the previously reported QTLs. qCrack-LG1.1m (the label given to a consistent QTL for cracking incidence on chromosome 1) explained 2-15.1% of the phenotypic variance, while qCrack-LG5.1m, qFirm-LG1.2m, and qFirm-LG3.2m explained 7.6-13.8, 8.8-21.8, and 1.7-10.1% of the phenotypic variance, respectively. At each QTL, at least two SNP haplotypes had significant effects and were considered putative functional SNP haplotypes. Putative low-cracking SNP haplotypes were tracked to an unnamed parent of 'Emperor Francis' and 'Schmidt' and unnamed parents of 'Napoleon' and 'Hedelfingen,' among others, and putative high-firmness haplotypes were tracked to an unnamed parent of 'Emperor Francis' and 'Schmidt,' an unnamed grandparent of 'Black Republican,' 'Rube,' and an unknown parent of 'Napoleon.' These four stable QTLs can now be targeted for DNA test development, with the goal of translating information discovered here into usable tools to aid in breeding decisions.

Probing the effects of sweet cherry (Prunus avium L.) extract on 2D and 3D human skin models

BACKGROUND

Natural products are not only positioned in the heart of traditional medicine but also in modern medicine as many current drugs are coming from natural sources. Apart from the field of medicine and therapeutics, natural products are broadly used in other industrial fields such as nutrition, skincare products and nanotechnology.

METHODS AND RESULTS

The aim of this study was to assess the effects of sweet cherry (Prunus avium L.) fruit extract from the Greek native cultivar 'Vasiliadi', on the human 2D and 3D in vitro models in order to investigate its potential impact on skin. We focused on 2D culture of primary normal human epidermal keratinocytes (NHEK) that were treated with sweet cherry fruit extract. In the first place, we targeted fruit extract potential cytotoxicity by determining ATP intracellular levels. Furthermore, we assessed its potential skin irritability by using 3D skin model. To better understand the bioactivity of sweet cherry fruit. extract, we used qPCR to study the expression of various genes that are implicated in the skin functions. Our experiments showed that sweet cherry fruit extract is non-toxic in 2D keratinocytes culture as well as non-irritant in 3D skin model. Our results revealed that the extract mediated important pathways for the optimum epidermis function such as cell proliferation, immune and inflammatory response.

CONCLUSION

The sweet cherry fruit extracts possesses significant activity in epidermis function without any potential of cytotoxicity or skin irritability, which makes it a rather promising active agent for skincare.

Rootstock Affects the Fruit Quality of 'Early Bigi' Sweet Cherries

The cherry rootstock influences the performance of the scion cultivar. It has an effect on cherry fruit quality, tree growth, yield and yield efficiency and floral and foliar nutrition. In this work, the influence of Saint Lucie 64 and Maxma 60 rootstocks on the fruit quality traits of cv. Early Bigi was evaluated. For this, several parameters, namely fruit weight (FW) and size (FS), soluble solids content (SSC), pH, titratable acidity (TA), flesh firmness (FF), epidermis rupture force (ERF), color and sensory profile, were assessed. Results showed that the fruits from trees on Saint Lucie 64 presented higher FF and ERF values and, consequently, better texture. On the other hand, fruits from trees on Maxma 60 showed sweeter cherries (higher SSC). Moreover, these trees presented the darkest cherries (lower values of L*, a*, b*, C* and hue°) and the highest SSC. Therefore, although the trees on Saint Lucie 64 produced firmer cherries, it was those with the Maxma 60 rootstock that produced sweeter and darker fruits. In conclusion, both scion–rootstock combinations proved to be good options for the region of Resende.

Valorisation of Prunus avium L. By-Products: Phenolic Composition and Effect on Caco-2 Cells Viability

Prunus avium L. by-products, such as stems, leaves, and flowers, are used in folk medicine to prevent and treat some diseases. However, their phenolic composition and in vitro bioactivities against tumor cells are poorly known. In this work, we compared the phenolic profile and the biological potential of aqueous infusions and hydroethanolic extracts of P. avium leaves, stems, and flowers from Saco cultivar, collected from the Fundão region (Portugal). Among the fifty-two phenolic compounds tentatively identified by HPLC-DAD-ESI/MSⁿ, the hydroxycinnamic acids were the most abundant. Both extracts of stems revealed a higher activity against DPPH^•. Meanwhile, hydroethanolic extracts from stems and flowers and aqueous infusions of flowers were the most effective in inhibiting the growth of the human epithelial colorectal adenocarcinoma (Caco-2) cells at concentrations above 200 μg/mL. More detailed knowledge about the phenolic composition and health-promoting properties of Portuguese P. avium by-products allows for increasing the biological and commercial value of these bio-wastes, which may have a positive impact on food and pharmaceutical industries, as on the valorization of the local economy.

Plant-Based Biostimulant as Sustainable Alternative to Synthetic Growth Regulators in Two Sweet Cherry Cultivars

Sweet cherry is a high value crop and the economic success of its cultivation depends not only on yield but also on fruit visual and nutritional quality attributes that influence consumer acceptability, as well as on fruit post-harvest performance and resistance to cracking. During the last few decades, cherry growers have tried to achieve these goals through exogenous applications of synthetic plant hormones and/or nutrients, but there is growing concern about the sustainability of the extensive use of these compounds in agriculture. For this reason, there is increasing interest in the possible adoption of different classes of biostimulants as sustainable alternatives to plant growth regulators. This research aimed to study the impact of foliar application of a novel tropical-plant extract, performed between full bloom and fruit set, on the yield and fruit quality of two important commercial sweet cherry cultivars, Kordia and Regina. The experimental design included a commercial control involving the application of a cytokinin promoter. In both cultivars, the tropical-plant extract induced significant increases in fruit yield. In addition, in the cultivar Kordia, the tropical-plant extract enhanced fruit calcium concentration, soluble solids content, flesh firmness, and skin color by 26.2%, 11.8%, 6.7%, and 12.0% (of fruits with mahogany skin color), respectively. Our results suggest that the tropical-plant extract tested as a biostimulant may be a sustainable and effective alternative to the exogenous application of synthetic hormones for sweet cherry cultivation.

Preliminary Insights in Sensory Profile of Sweet Cherries

Sweet cherry (Prunus avium L.) is a fruit appreciated by consumers for its well-known physical and sensory characteristics and its health benefits. Being an extremely perishable fruit, it is important to know the unique attributes of the cultivars to develop cultivation or postharvest strategies that can enhance their quality. This study aimed to understand the influence of physicochemical characteristics of two sweet cherry cultivars, Burlat and Van, on the food quality perception. Several parameters (weight, dimensions, soluble solids content (SSC), pH, titratable acidity (TA), colour, and texture) were measured and correlated with sensory data. Results showed that cv. Van presented heavier and firmer fruits with high sugar content. In turn, cv. Burlat showed higher pH, lower TA, and presented redder and brightest fruits. The principal component analysis revealed an evident separation between cultivars. Van cherries stood out for their sensory parameters and were classified as more acidic, bitter, and astringent, and presented a firmer texture. Contrarily, Burlat cherries were distinguished as being more flavourful, succulent, sweeter, and more uniform in terms of visual and colour parameters. The results of the sensory analysis suggested that perceived quality does not always depend on and/or recognize the quality parameters inherent to the physicochemical characteristics of each cultivar.

Differential Tissue-Specific Jasmonic Acid, Salicylic Acid, and Abscisic Acid Dynamics in Sweet Cherry Development and Their Implications in Fruit-Microbe Interactions

Sweet cherry is an important non-climacteric fruit with a high commercial interest, but exploitation of sweet cherry trees (Prunus avium L.) in orchards is usually subject to important economic losses due to fruit decay by pathogenic fungi and other microorganisms. Sweet cherries development and ripening are characterized by profound physiological changes in the fruit, among which the phytohormone abscisic acid (ABA) plays a pivotal role. In addition, sweet cherries are usually affected by fruit decay pathogens, and the role of other stress-related hormones such as jasmonic acid (JA) and salicylic acid (SA) may also be of paramount importance, not only from a developmental point of view, but also from a fruit-microbe interaction perspective. Here, a tissue-specific hormone quantification by LC-MS/MS, including the contents of JA, SA, and ABA, in the fruit exocarp and mesocarp of sweet cherries during fruit development from trees growing in a commercial orchard was carried out. Additionally, this study was complemented with the characterization of the culturable epiphytic and endophytic microbial communities of sweet cherries at various stages of fruit development and during cracking lesion formation. Our results revealed a completely differential behavior of phytohormones between both tissues (the exocarp and mesocarp), with a more dynamic exocarp in front of a more stable mesocarp, and with marked variations during fruit development. Microbial epiphytic community was mainly composed by yeasts, although rot-causing fungi like Alternaria spp. were always also present throughout fruit development. Endophytic colonization was poor, but it increased throughout fruit development. Furthermore, when the exocarp was naturally disrupted in sweet cherries suffering from cracking, the colonization by Alternaria spp. markedly increased. Altogether, results suggest that the fruit exocarp and mesocarp are very dynamic tissues in which endogenous phytohormones not only modulate fruit development and ripening but also fruit-microbe interactions.

Quality preservation of sweet cherry cv. 'staccato' by using glycine-betaine or Ascophyllum nodosum

Pre-harvest application of exogenous compounds has been employed in many crops, as a cultural practice, to promote their adaptation to a new climate-changing environment. Effect of foliar pre-harvest application of salicylic acid, glycine-betaine complex and seaweed extract (Ascophyllum nodosum) on the cherry quality from 'Staccato' cultivar was studied. Treatments significantly affected (p < 0.01) the fruit size, soluble solids content, pH, colour, polyphenols, vitamin C and antioxidant activity. Glycine-betaine and A. nodosum treated cherries presented higher dimensions, soluble solids content and pH and lower acidity. In addition, these cherries had a higher content of polyphenols and vitamin C and antioxidant capacity, but lower values of L*, C*ab and hue angle, meaning that both treatments can rise the fruit ripening process. Therefore, the pre-harvest application of glycine-betaine and A. nodosum can be a good alternative to promote the adaptation of sweet cherry tree to stressful environmental conditions, without compromising the fruit quality.

Fruit Quality Characterization of New Sweet Cherry Cultivars as a Good Source of Bioactive Phenolic Compounds with Antioxidant and Neuroprotective Potential

Sweet cherries (Prunus avium L.) are highly appreciated fruits for their taste, color, nutritional value, and beneficial health effects. In this work, seven new cultivars of sweet cherry were investigated for their main quality traits and nutraceutical value. The phytochemical profile of three classes of phenolic compounds and the antioxidant activity of the new cultivars were investigated through high-performance liquid chromatography with diode array detection (HPLC-DAD) and spectrophotometric assays, respectively, and compared with those of commonly commercialized cultivars. Cyanidine-3-O-rutinoside was the main anthocyanin in all genotypes, and its levels in some new cultivars were about three-fold higher than in commercial ones. The ORAC-assayed antioxidant capacity was positively correlated with the total anthocyanin index. The nutraceutical value of the new cultivars was investigated in terms of antioxidant/neuroprotective capacity in neuron-like SH-SY5Y cells. Results demonstrated that the new cultivars were more effective in counteracting oxidative stress and were also able to upregulate brain-derived neurotrophic factor (BDNF), a pro-survival neurotrophin, suggesting their potential pleiotropic role in counteracting neurodegenerations.

Effects of exogenous compound sprays on cherry cracking: skin properties and gene expression

BACKGROUND

Cherry fruit cracking is a costly problem for cherry growers. The effect of repeated sprayings (gibberellic acid - GA₃ ; abscisic acid - ABA; salicylic acid - SA; glycine betaine - GB, and Ascophyllum nodosum - AN) combined with CaCl₂ , on 'Sweetheart' cherry fruit-cracking characteristics was investigated. Cracking was quantified in terms of cracking incidence, crack morphology, confocal scanning laser microscopy, cuticular wax content, cell-wall modification, and cuticular wax gene expression.

RESULTS

All spray treatments reduced cracking compared with an untreated control (H₂ O), with fewer cheek cracks. The least cracking incidence was observed for ABA + CaCl₂ - and GB + CaCl₂ -treated fruits, indicating an added benefit compared to spraying with CaCl₂ alone. In addition, GB + CaCl₂ -treated fruits showed higher fruit diameter. ABA + CaCl₂ and GB + CaCl₂ sprays showed higher wax content and higher cuticle and epidermal thickness compared with the control, including increased expression of wax synthase (ABA + CaCl₂ ) and expansin 1 (GB + CaCl₂ ).

CONCLUSION

In general, factors that improve the cuticle thickness appear to be important at the fruit-coloring stage. At the fruit-ripening stage, larger cell sizes of the epidermis, hypodermis, and parenchyma cells lower cracking incidence, indicating the importance of flexibility and elasticity of the epidermis. © 2020 Society of Chemical Industry.

A Comparison of the Variable J and Carbon-Isotopic Composition of Sugars Methods to Assess Mesophyll Conductance from the Leaf to the Canopy Scale in Drought-Stressed Cherry

Conductance of CO2 across the mesophyll (Gm) frequently constrains photosynthesis (PN) but cannot be measured directly. We examined Gm of cherry (Prunus avium L.) subjected to severe drought using the variable J method and carbon-isotopic composition (δ13C) of sugars from the centre of the leaf, the leaf petiole sap, and sap from the largest branch. Depending upon the location of the plant from which sugars are sampled, Gm may be estimated over scales ranging from a portion of the leaf to a canopy of leaves. Both the variable J and δ13C of sugars methods showed a reduction in Gm as soil water availability declined. The δ13C of sugars further from the source of their synthesis within the leaf did not correspond as closely to the diffusive and C-isotopic discrimination conditions reflected in the instantaneous measurement of gas exchange and chlorophyll-fluorescence utilised by the variable J approach. Post-photosynthetic fractionation processes and/or the release of sugars from stored carbohydrates (previously fixed under different environmental and C-isotopic discrimination conditions) may reduce the efficacy of the δ13C of sugars from leaf petiole and branch sap in estimating Gm in a short-term study. Consideration should be given to the spatial and temporal scales at which Gm is under observation in any experimental analysis.

Influence of Regulated Deficit Irrigation and Environmental Conditions on Reproductive Response of Sweet Cherry Trees

The reproductive response of fifteen year old sweet cherry trees (Prunus avium L.) combination 'Prime Giant'/SL64 under Mediterranean climate to deficit irrigation was studied in a commercial orchard in south-eastern Spain for four seasons. Three irrigation treatments were assayed: (i) control treatment, irrigated without restrictions at 110% of seasonal crop evapotranspiration; (ii) sustained deficit irrigation treatment, irrigated at 85% ET_c during pre-harvest and post-harvest periods, and at 100% ET_c during floral differentiation, and (iii) regulated deficit irrigation treatment, irrigated at 100% ET_c during pre-harvest and floral differentiation and at 55% ET_c during post-harvest. The duration and intensity of the phenological phases of sweet cherry trees, including cold accumulation, flowering, fruit set or fruit and vegetative growth, were assessed to ascertain whether the different irrigation strategies imposed affect the trees' reproductive response (fruit yield, fruit size, leaf area, fruit physiological disturbances, and starch and soluble carbohydrates stock) in the same season or have a negative effect in the next season. Deficit irrigation did not advance, enhance or penalize flowering, fruit set or fruit growth. Neither did it diminish carbohydrate concentration in roots or cause an increase in the number of double fruits, which was more linked to high temperatures after harvest. However, deficit irrigation decreased vegetative growth and consequently the leaf area/fruit ratio, which, when it fell below 180 cm² fruit^-1, affected cherry size.

From bud formation to flowering: transcriptomic state defines the cherry developmental phases of sweet cherry bud dormancy

Background

Bud dormancy is a crucial stage in perennial trees and allows survival over winter to ensure optimal flowering and fruit production. Recent work highlighted physiological and molecular events occurring during bud dormancy in trees. However, they usually examined bud development or bud dormancy in isolation. In this work, we aimed to further explore the global transcriptional changes happening throughout bud development and dormancy onset, progression and release.

Results

Using next-generation sequencing and modelling, we conducted an in-depth transcriptomic analysis for all stages of flower buds in several sweet cherry (Prunus avium L.) cultivars that are characterized for their contrasted dates of dormancy release. We find that buds in organogenesis, paradormancy, endodormancy and ecodormancy stages are defined by the expression of genes involved in specific pathways, and these are conserved between different sweet cherry cultivars. In particular, we found that DORMANCY ASSOCIATED MADS-box (DAM), floral identity and organogenesis genes are up-regulated during the pre-dormancy stages while endodormancy is characterized by a complex array of signalling pathways, including cold response genes, ABA and oxidation-reduction processes. After dormancy release, genes associated with global cell activity, division and differentiation are activated during ecodormancy and growth resumption. We then went a step beyond the global transcriptomic analysis and we developed a model based on the transcriptional profiles of just seven genes to accurately predict the main bud dormancy stages.

Conclusions

Overall, this study has allowed us to better understand the transcriptional changes occurring throughout the different phases of flower bud development, from bud formation in the summer to flowering in the following spring. Our work sets the stage for the development of fast and cost effective diagnostic tools to molecularly define the dormancy stages. Such integrative approaches will therefore be extremely useful for a better comprehension of complex phenological processes in many species.

The Profile and Content of Polyphenols and Carotenoids in Local and Commercial Sweet Cherry Fruits (Prunus avium L.) and Their Antioxidant Activity In Vitro

The aim of this study was to evaluate and compare the content of a number of bioactive compounds and antioxidant activity of fruits of selected local and commercial sweet cherry (Prunus avium L.) cultivars. The experiment showed that the selected cultivars of sweet cherries differ significantly in the content of polyphenolic compounds and carotenoids. The fruits of commercial sweet cherry cultivars were, on average, richer in polyphenols (the sum of phenolic compounds determined chromatographically), flavonoids, as well as anthocyanins and were characterized by higher antioxidant activity when compared to the local, traditional cultivars. In the group of the traditional sweet cherry cultivars, particular attention could be paid to Black Late cv., showing the highest antioxidant activity of fruits. In the group of commercial sweet cherry cultivars, Cordia and Sylvia fruits could be recognized as being rich in bioactive compounds with high antioxidant activity. Yellow skin cultivars were characterized by the highest concentrations of carotenoids. Strong positive correlations between the identified bioactive compounds and antioxidant activity of fruits were also found. Although different cultivars of sweet cherries show a high variability in phenolics and carotenoids profiles as well as in the antioxidant activity of fruits, they all should be, similarly to other types of cherries, recognized as a rich source of bioactive compounds with an antioxidant potential.

Melatonin as an inhibitor of sweet cherries ripening in orchard trees

Although melatonin effects on postharvest fruit ripening have been studied in some detail, information is still scarce during pre-harvest. Here, we examined whether or not melatonin may exert a regulatory role during sweet cherries ripening in orchard trees. We evaluated (i) the endogenous variations in melatonin contents, in comparison to those of well-known phytohormones such as ABA, salicylic acid and jsamonic acid, by ultrahigh performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) during fruit ripening over two consecutive years, and (ii) to what extent melatonin treatments at low and high concentrations (at 10^-4 M and 10^-5 M, respectively) influence fruit ripening on the tree. Endogenous melatonin contents decreased in parallel to those of salicylic acid and jasmonic acid, while ABA contents increased as fruit ripening progressed, thus suggesting an inhibitory role for melatonin in fruit ripening. Furthermore, melatonin treatment at 10^-5 M, which transiently increased endogenous melatonin contents at physiological concentrations, delayed anthocyanin accumulation, thus confirming an inhibitory regulatory role for melatonin in fruit ripening. We also found that the endogenous contents of cytokinins, but not those of ABA were transiently affected by melatonin treatment at 10^-5 M. It is concluded that melatonin may delay sweet cherries ripening in orchard trees, probably exerting a modulatory role through a hormonal cross-talk. These results have important implications for the use of melatonin in the control of the timing of sweet cherries ripening in orchard trees.

Sweet cherry water relations and fruit production efficiency are affected by rootstock vigor

Rootstock vigor is well known to affect yield and productive performance in many fruit crops and the dwarfing trait is often the preferred choice for modern orchard systems thanks to its improved productivity and reduced canopy volume. This work investigates the different physiological responses induced by rootstock vigor on cherry, by comparing shoot and fruit growth, water relations, leaf gas exchanges as well as fruit vascular and transpiration in/outflows of "Black Star" trees grafted on semi-vigorous (CAB6 P) and on semi-dwarfing (Gisela™6) rootstocks. The daily patterns of stem (Ψ_stem), leaf (Ψ_leaf) and fruit (Ψ_fruit) water potential, leaf photosynthesis, stomatal conductance and transpiration, shoot and fruit growth, fruit phloem, xylem and transpiration flows were assessed both in pre- and post-veraison, while productivity and fruit quality were determined at harvest. At both stages, no significant differences were found on Ψ_leaf, photosynthesis, fruit daily growth rates as well as fruit vascular and transpiration flows, while trees on Gisela™6 showed lower shoot growth rates and lower Ψ_stem and Ψ_fruit than trees on CAB6 P. The resulting decrease in stem-to-leaf Ψ gradient on Gisela™6 trees determined a reduction in shoot growth by decreasing shoot strength as sinks for water and carbohydrates. On the other hand, Gisela™6 fruit lowered their Ψ_fruit thanks to a higher osmotic accumulation and increased their competitiveness towards shoots, as confirmed by the higher productivity and fruit soluble solid content found at harvest for these trees. These results indicate that rootstock vigor alters resource competition between vegetative and reproductive growth, which can affect water use efficiency, yield, and fruit quality.

Tuscan Varieties of Sweet Cherry Are Rich Sources of Ursolic and Oleanolic Acid: Protein Modeling Coupled to Targeted Gene Expression and Metabolite Analyses

The potential of six ancient Tuscan sweet cherry (Prunus avium L.) varieties as a source of health-promoting pentacyclic triterpenes is here evaluated by means of a targeted gene expression and metabolite analysis. By using a sequence homology criterion, we identify five oxidosqualene cyclase genes (OSCs) and three cytochrome P450s (CYP85s) that are putatively involved in the triterpene production pathway in sweet cherries. We performed 3D structure prediction and induced-fit docking using cation intermediates and reaction products for some OSCs to predict their function. We show that the Tuscan varieties have different amounts of ursolic and oleanolic acids and that these variations are related to different gene expression profiles. This study stresses the interest of valorizing ancient fruits as alternative sources of functional molecules with nutraceutical value. It also provides information on sweet cherry triterpene biosynthetic genes, which could be the object of follow-up functional studies.

Exploring the phenolic profile, antioxidant, antidiabetic and anti-hemolytic potential of Prunus avium vegetal parts

The aim of the present work was to evaluate the phenolic profile of leaves, stems and flowers of P. avium and their biological potential. For this purpose, two extracts of each matrix (hydroethanolic and infusion) were prepared. A total of twenty-six phenolics were identified by LC-DAD, including 1 hydroxybenzoic acid, 9 hydroxycinnamic acids, 7 flavonols, 3 isoflavones, 3 flavanones and 3 flavan-3-ols, being the hydroethanolic leaves extract the richest one. 5-O-caffeoylquinic acid, hydroxycinnamic derivative 1 and sakuranetin derivative were the major compounds found in leaves, flowers and stems, respectively. The hydroethanolic extracts of stems and leaves proved to be the most active against DPPH^• and O₂^•- (IC₅₀ = 22.37 ± 0.29 μg/mL and IC₅₀ = 9.11 ± 0.16 μg/mL, respectively). On the other hand, the infusion extract of stems showed the highest antioxidant activity against ^•NO (IC₅₀ = 99.99 ± 1.89 μg/mL). The antidiabetic potential was tested using the α-glucosidase enzyme, being the infusion extract of stems the most active, with an IC₅₀ = 3.18 ± 0.23 μg/mL. Finally, the protective effect of the extracts towards human erythrocytes against oxidative damage was also evaluated. The hydroethanolic extract of stems was the most active against lipid peroxidation and hemolysis with an IC₅₀ = 26.20 ± 0.38 μg/mL and IC₅₀ = 1.58 ± 0.18 μg/mL, respectively. On the other hand, the hydroethanolic extract of flowers showed the greater protective effect against hemoglobin oxidation (IC₅₀ = 12.85 ± 0.61 μg/mL). Considering the results obtained in this work, we can consider that leaves, stems and flowers of P. avium are a promising source of bioactive compounds and present health-promoting properties.

Non-anthocyanin phenolics in cherry (Prunus avium L.) modulate IL-6, liver lipids and expression of PPARδ and LXRs in obese diabetic (db/db) mice

Anthocyanin-rich cherries are known for preventing/decreasing risk factors associated with obesity; however, the specific benefits exerted by cherry non-anthocyanin phenolics are not clear. Obese diabetic (db/db) mice fed a diet supplemented with anthocyanin-depleted cherry powder (cherry) were compared to db/db (obese) or lean counterparts (lean) fed a control isocaloric diet for 12 weeks. The reduced plasma interleukin (IL)-6 and improved liver health may be mediated by cherry fibre and non-anthocyanin phenolics. Benefits for liver health included reduction of lipids and protein carbonyls, and modulation of peroxisome proliferator-activated receptor (PPAR)δ mRNA to resemble levels in lean. Lack of plasma antilipidemic, improvement of antioxidant defenses, and PPARα/γ mRNA modulation in liver suggest cherry anthocyanins specific benefits. This is the first study to elucidate in vivo the potential benefits of cherry non-anthocyanin phenolics for diabetes-induced liver disorders and the importance of choosing processing technologies that preserve anthocyanins and health benefits of whole cherries.

Selected Plant Metabolites Involved in Oxidation-Reduction Processes during Bud Dormancy and Ontogenetic Development in Sweet Cherry Buds (Prunus avium L.)

Many biochemical processes are involved in regulating the consecutive transition of different phases of dormancy in sweet cherry buds. An evaluation based on a metabolic approach has, as yet, only been partly addressed. The aim of this work, therefore, was to determine which plant metabolites could serve as biomarkers for the different transitions in sweet cherry buds. The focus here was on those metabolites involved in oxidation-reduction processes during bud dormancy, as determined by targeted and untargeted mass spectrometry-based methods. The metabolites addressed included phenolic compounds, ascorbate/dehydroascorbate, reducing sugars, carotenoids and chlorophylls. The results demonstrate that the content of phenolic compounds decrease until the end of endodormancy. After a long period of constancy until the end of ecodormancy, a final phase of further decrease followed up to the phenophase open cluster. The main phenolic compounds were caffeoylquinic acids, coumaroylquinic acids and catechins, as well as quercetin and kaempferol derivatives. The data also support the protective role of ascorbate and glutathione in the para- and endodormancy phases. Consistent trends in the content of reducing sugars can be elucidated for the different phenophases of dormancy, too. The untargeted approach with principle component analysis (PCA) clearly differentiates the different timings of dormancy giving further valuable information.

Climate change and spring frost damages for sweet cherries in Germany

Spring frost can be a limiting factor in sweet cherry (Prunus avium L.) production. Rising temperatures in spring force the development of buds, whereby their vulnerability to freezing temperatures continuously increases. With the beginning of blossom, flowers can resist only light frosts without any significant damage. In this study, we investigated the risk of spring frost damages during cherry blossom for historical and future climate conditions at two different sites in NE (Berlin) and SW Germany (Geisenheim). Two phenological models, developed on the basis of phenological observations at the experimental sweet cherry orchard in Berlin-Dahlem and validated for endodormancy release and for warmer climate conditions (already published), were used to calculate the beginning of cherry blossom in Geisenheim, 1951-2015 (external model validation). Afterwards, on the basis of a statistical regionalisation model WETTREG (RCP 8.5), the frequency of frost during cherry blossom was calculated at both sites for historical (1971-2000) and future climate conditions (2011-2100). From these data, we derived the final flower damage, defined as the percentage of frozen flowers due to single or multiple frost events during blossom. The results showed that rising temperatures in this century can premature the beginning of cherry blossom up to 17 days at both sites, independent of the used phenological model. The frequency and strength of frost was characterised by a high temporal and local variability. For both sites, no significant increase in frost frequency and frost damage during blossom was found. In Geisenheim, frost damages significantly decreased from the middle of the twenty-first century. This study additionally emphasises the importance of reliable phenological models which not only work for current but also for changed climate conditions and at different sites. The date of endodormancy release should always be a known parameter in chilling/forcing models.

Biochemical and physiological changes during fruit development and ripening of two sweet cherry varieties with different levels of cracking tolerance

The aim of this study was to investigate the biochemical and metabolic changes, related to oxidative stress, ethylene and respiration, cell wall modification and primary metabolism, between a high ('Prime Giant') and a low ('Cristalina') cracking susceptible sweet cherry cultivar during growth and ripening. While cherries are referred as a non-climacteric fruit, our results show that an increase of endogenous ethylene production at earlier fruit developmental stages is parallel to colour development and softening during growth. Higher cracking susceptibility was clearly associated to a higher fruit growth rate and accompanied by an increase net CO₂ and ethylene production, on a cherry basis, leading to an enhanced accumulation of oxidative stress markers (i.e. H₂O₂ and MDA). As observed in other fruit species (i.e. tomatoes) higher cracking susceptibility was also related to enhanced activity of cell wall-modifying enzymes which in turn occurred in parallel to the ethylene rise. Overall, these results suggest that cracking development may be a more complex phenomenon than a mere consequence of altered fruit water absorption or turgor and point out the importance of ethylene on sweet cherry ripening and cracking development.

Quality and antioxidant properties on sweet cherries as affected by preharvest salicylic and acetylsalicylic acids treatments

The effects of salicylic acid (SA) or acetylsalicylic acid (ASA) treatments during on-tree cherry growth and ripening on fruit quality attributes, especially those related with the content on bioactive compounds and antioxidant activity were analysed in this research. For this purpose, two sweet cherry cultivars, 'Sweet Heart' and 'Sweet Late', were used and SA or ASA treatments, at 0.5, 1.0 and 2.0mM concentrations, were applied at three key points of fruit development (pit hardening, initial colour changes and onset of ripening). These treatments increased fruit weight and ameliorated quality attributes at commercial harvest, and led to cherries with higher concentration in total phenolics and in total anthocyanins, as well as higher antioxidant activity, in both hydrophilic and lipophilic fractions. Thus, preharvest treatments with SA or ASA could be promising tools to improve sweet cherry quality and health beneficial effects for consumers.

Genetic diversity and relatedness of sweet cherry (prunus avium L.) cultivars based on single nucleotide polymorphic markers

Most previous studies on genetic fingerprinting and cultivar relatedness in sweet cherry were based on isoenzyme, RAPD, and simple sequence repeat (SSR) markers. This study was carried out to assess the utility of single nucleotide polymorphism (SNP) markers generated from 3' untranslated regions (UTR) for genetic fingerprinting in sweet cherry. A total of 114 sweet cherry germplasm representing advanced selections, commercial cultivars, and old cultivars imported from different parts of the world were screened with seven SSR markers developed from other Prunus species and with 40 SNPs obtained from 3' UTR sequences of Rainier and Bing sweet cherry cultivars. Both types of marker study had 99 accessions in common. The SSR data was used to validate the SNP results. Results showed that the average number of alleles per locus, mean observed heterozygosity, expected heterozygosity, and polymorphic information content values were higher in SSRs than in SNPs although both set of markers were similar in their grouping of the sweet cherry accessions as shown in the dendrogram. SNPs were able to distinguish sport mutants from their wild type germplasm. For example, "Stella" was separated from "Compact Stella." This demonstrates the greater power of SNPs for discriminating mutants from their original parents than SSRs. In addition, SNP markers confirmed parentage and also determined relationships of the accessions in a manner consistent with their pedigree relationships. We would recommend the use of 3' UTR SNPs for genetic fingerprinting, parentage verification, gene mapping, and study of genetic diversity in sweet cherry.