Sweet Cherry Fruit Research Articles

Large-fragment deletion encompasses the R2R3 MYB transcription factor, PavMYB10.1, causes yellow fruits in sweet cherry (Prunus avium L.)

Due to different accumulation and distribution patterns of anthocyanin, the fruits of sweet cherry (Prunus avium L.) display considerable color variation, ranging from yellow, blush to dark red. Yellow-skinned sweet cherries are characterized by the absence of anthocyanin in the fruits, providing a good candidate for research on yellow coloration in sweet cherry fruits. In this study, we identified the underlying genetic mechanism by integrating BSA-seq, RNA-seq, whole-genome sequencing and marker-trait association analyses. A ∼90 kb deletion on chromosome 3 containing PavMYB10.1 TF was found to be an nonfunctional allele, PavMYB10.1Del, responsible for yellow fruit skin. Other two functional alleles of PavMYB10.1, PavMYB10.1a and PavMYB10.1b, result in red or blush skin color. Furthermore, evaluation of variant-trait association in F1 populations and a set of advanced breeding selections revealed strong co-segregation of the fruit skin color phenotypes and the EFC marker which combined by primers specific to PavMYB10.1a/b and PavMYB10.1Del separately. These results provide novel insights into yellow fruit skin coloration in sweet cherry and represent a useful tool for the pre-selection of fruit color in molecular-assisted breeding programs.

Fruit Quality and Contents of Some Bioactive Compounds in Selected Czech Sweet Cherry (Prunus avium L.) Cultivars under Conditions of Central Poland

Dynamic changes have taken place in the production of sweet cherry (Prunus avium L.) in Poland over the last 20 years. New cultivars with both early- and late-ripening dates have appeared, and modern high-intensity cultivation techniques are being implemented. The main attribute of the fruit, in addition to its unique taste, is its health-promoting properties. In this research, which was conducted at the Warsaw University of Life Sciences in 2021, our main objectives were to evaluate seven selected Czech cherry cultivars (‘Jacinta’; ‘Horka’; ‘Tamara’; ‘Helga’; ‘Fabiola’; ‘Kasandra’; ‘Kordia’) with regard to their dessert quality and contents of biologically active compounds, and to indicate the most valuable cultivar under the conditions of central Poland. The cultivars tested differed in both the fruit quality and health-promoting properties. ‘Jacinta’, ‘Horka’, Tamara’ and ‘Fabiola’ had the largest fruits. The ‘Fabiola’ and ‘Kordia’ fruits had the highest firmness, while the ‘Jacinta’ and ‘Horka’ fruits had the highest soluble solid contents (SSCs) and titratable acidities (TAs). We found the highest SSC-to-TA ratio in the ‘Fabiola’ cultivar. ‘Jacinta’ proved to be the most valuable cultivar in terms of bioactive compounds, and it had the highest antioxidant activity (DPPH). Some of the traits were closely correlated with each other, mainly in relation to the biologically active compounds. Darker fruits contained more bioactive compounds and had a higher antioxidant activity. It was also proved that size of fruits as well as SSC and TA are also correlated with fruit color. Intensively colored fruit are larger and have higher SSC and TA. In sweet cherry fruit, the contents of polyphenols and flavonoids, as well as the high DPPH, are strongly determined by the high content of cyanidin-3-galactoside.

The PavNAC56 transcription factor positively regulates fruit ripening and softening in sweet cherry (Prunus avium).

The rapid softening of sweet cherry fruits during ripening results in the deterioration of fruit quality. However, few genes related to sweet cherry fruit ripening and softening have been identified, and the molecular regulatory mechanisms underlying this process are poorly understood. Here, we identified and functionally characterized PavNAC56, a NAC transcription factor that positively regulates sweet cherry fruit ripening and softening. Gene expression analyses showed that PavNAC56 was specifically and abundantly expressed in the fruit, and its transcript levels increased in response to abscisic acid (ABA). A subcellular localization analysis revealed that PavNAC56 is a nucleus-localized protein. Virus-induced gene silencing of PavNAC56 inhibited fruit ripening, enhanced fruit firmness, decreased the contents of ABA, anthocyanins, and soluble solids, and down-regulated several fruit ripening-related genes. Yeast one-hybrid and dual-luciferase assays showed that PavNAC56 directly binds to the promoters of several genes related to cell wall metabolism (PavPG2, PavEXPA4, PavPL18, and PavCEL8) and activates their expression. Overall, our findings show that PavNAC56 plays an indispensable role in controlling the ripening and softening of sweet cherry fruit and provides new insights into the regulatory mechanisms by which NAC transcription factors affect nonclimacteric fruit ripening and softening.

Analysis of the collision-damage susceptibility of sweet cherry related to environment temperature: A numerical simulating method

Sweet cherry is extremely susceptible to collision damage during post-harvest handling. Fruit-to-rigid surface and fruit-to-fruit collision systems were modeled by the dynamic FE method and the sweet cherry model included three parts: exocarp, mesocarp, and pit. A fruit-to-rigid surface horizontal collision testbed was newly developed to validate the prediction accuracy of the fruit FE model. It was found that the fruit model inputting the average elastic moduli and failure stress of the fruit tissues can reproduce the experimental maximum impact force and contact time in the compression stage with the relative error of 1.58 and 1.87%, respectively. Three mathematical models were proven to be capable of quantitatively assessing the internal damage degree of sweet cherry by three independent variables: collision type, initial fruit velocity, and environment temperature. This study shows an effective numerical simulation approach for objectively predicting the horizontal collision-damage susceptibility of sweet cherry and other fresh fruit in postharvest damage-prevention strategy analysis. • • Fruit FE model can reproduce two collision experimental mechanical parameters. • • Fruit damage volume increased nonlinearly with the collision contact time. • • The velocity change of the local tissue in fruit during collision was presented. • • The degree of fruit collision damage can be predicted by the obtained models. • • Collision type was the most key factor affecting the fruit damage susceptibility.

The Effect of Preharvest Application of Arginine on the Postharvest Quality of Sweet Cherry Fruits during Storage

ABSTRACT The quality of sweet cherry fruits decrease rapidly after harvest and in some cases does not reach the consumers properly due to the time require for transferring and market. Therefore, using chemical compounds is essential to increase durability and maintain its quality. This study was conducted to investigate the effects of arginine on postharvest quality of sweet cherry fruits. The sweet cherry fruits (Prunus avium L. cv TakDanehe Mashhad) were sprayed with arginine (0, 200, and 400 μM) one month before harvest. Fruits were harvested at commercial maturity stage according to acceptable color standards. After harvest, the fruits were transferred to the laboratory and immediately kept in cold storage with temperature of 1°C with 90–95% relative humidity (RH) for 20 days. The results showed that in treated fruits, electrolyte leakage, active oxygen production, and lipid peroxidation were decreased. The activity of antioxidant enzymes including ascorbate peroxidase, catalase, and superoxide dismutase was increased compared to control. The treated fruits with arginine 400 µM showed the highest enzymatic activity during cold storage. The percentage of chilling injury and fresh weight loss in treated fruits has decreased comparing control fruits. According to the results lowest amount of pH observed in fruits treated with arginine 400 µM. Arginine increased the amount of titratable acid, soluble solids, and vitamin C, as well the firmness of fruits. As short, arginine preharvest treatment at 400 µM concentration improved the postharvest quality of sweet cherry fruits.

Orchard microclimate, tree water uptake and sweet cherry fruit quality under protected cropping.

Protected cropping systems (PCS) de-risk adverse climatic effects in intensive horticultural production but alter the growing environment. The objectives of this study were to investigate the effects of modern, commercial-scale PCS on sweet cherry orchard microclimate, tree water uptake and fruit quality. Sap flow sensors and weather stations were positioned at four locations under a 21 ha PCS at varying elevations (125, 114, 111, 102 m above sea level) and distances from the block boundary (105, 75, 60 or 50 m, referred to hereafter as Locations 1 to 4, respectively). Generalised additive models (GAMs) were used to predict the effect of individual climate parameters (temperature, relative humidity, solar radiation and wind speed) on tree sap flow at each of the four locations. Average and maximum temperatures and average minimum relative humidity (RH) were higher (15.9°C, 26.1°C and 49.0%) at locations with higher elevations and located further from the PCS boundary (locations 1 and 2) in contrast to locations at lower elevations and closer proximity to the PCS boundary (locations 3 and 4) (15.4°C, 24.6°C and 48.1%). Predicted sap flow was strongly correlated (r2 = 0.92) with time across the four locations under the PCS. GAMS modelling indicated that the hourly water uptake by trees within close proximity to the block boundary (locations 3 and 4) responded with greater intensity to increases in temperature and reductions in relative humidity, taking up on average 0.15 L h-1 (at temperatures >30°C) and 0.08 L h-1 (at RH<50%), respectively, in contrast to trees further under the PCS (locations 1 and 2) where average tree water uptake was 0.08 and 0.04 L h-1 at temperatures >30°C and RH<50%, respectively. Highest average predicted hourly tree sap flow was associated with high wind speeds (0.67 L h-1) and low relative humidity levels (0.61 L h-1). Fruit harvested from locations further from the PCS boundary had significantly higher dry matter content (18.2%), total soluble solids (17.8%) and compression firmness (311.3 g mm-1) in contrast to fruit closer to the PCS boundaries (16.1%, 15.7% and 258.3 g mm-1). This study provides greater understanding of the effects of PCS on microclimate and consequences for tree water uptake and fruit quality.

A Real-Time Detection Algorithm for Sweet Cherry Fruit Maturity Based on YOLOX in the Natural Environment

Fast, accurate, and non-destructive large-scale detection of sweet cherry ripeness is the key to determining the optimal harvesting period and accurate grading by ripeness. Due to the complexity and variability of the orchard environment and the multi-scale, obscured, and even overlapping fruit, there are still problems of low detection accuracy even using the mainstream algorithm YOLOX in the absence of a large amount of tagging data. In this paper, we proposed an improved YOLOX target detection algorithm to quickly and accurately detect sweet cherry ripeness categories in complex environments. Firstly, we took a total of 2400 high-resolution images of immature, semi-ripe, and ripe sweet cherries in an orchard in Hanyuan County, Sichuan Province, including complex environments such as sunny days, cloudy days, branch and leaf shading, fruit overlapping, distant views, and similar colors of green fruits and leaves, and formed a dataset dedicated to sweet cherry ripeness detection by manually labeling 36068 samples, named SweetCherry. On this basis, an improved YOLOX target detection algorithm YOLOX-EIoU-CBAM was proposed, which embedded the Convolutional Block Attention Module (CBAM) between the backbone and neck of the YOLOX model to improve the model’s attention to different channels, spaces capability, and replaced the original bounding box loss function of the YOLOX model with Efficient IoU (EIoU) loss to make the regression of the prediction box more accurate. Finally, we validated the feasibility and reliability of the YOLOX-EIoU-CBAM network on the SweetCherry dataset. The experimental results showed that the method in this paper significantly outperforms the traditional Faster R-CNN and SSD300 algorithms in terms of mean Average Precision (mAP), recall, model size, and single-image inference time. Compared with the YOLOX model, the mAP of this method is improved by 4.12%, recall is improved by 4.6%, F-score is improved by 2.34%, while model size and single-image inference time remain basically comparable. The method in this paper can cope well with complex backgrounds such as fruit overlap, branch and leaf occlusion, and can provide a data base and technical reference for other similar target detection problems.

Copper Amine Oxidase (CuAO)-Mediated Polyamine Catabolism Plays Potential Roles in Sweet Cherry (Prunus avium L.) Fruit Development and Ripening

Copper amine oxidases (CuAOs) play important roles in PA catabolism, plant growth and development, and abiotic stress response. In order to better understand how PA affects cherry fruit, four potential PavCuAO genes (PavCuAO1–PavCuAO4) that are dispersed over two chromosomes were identified in the sweet cherry genome. Based on phylogenetic analysis, they were classified into three subclasses. RNA-seq analysis showed that the PavCuAO genes were tissue-specific and mostly highly expressed in flowers and young leaves. Many cis-elements associated with phytohormones and stress responses were predicted in the 2 kb upstream region of the promoter. The PavCuAOs transcript levels were increased in response to abscisic acid (ABA) and gibberellin 3 (GA3) treatments, as well as abiotic stresses (NaCl, PEG, and cold). Quantitative fluorescence analysis and high-performance liquid chromatography confirmed that the Put content fell, and the PavCuAO4 mRNA level rose as the sweet cherry fruit ripened. After genetically transforming Arabidopsis with PavCuAO4, the Put content in transgenic plants decreased significantly, and the expression of the ABA synthesis gene NCED was also significantly increased. At the same time, excessive H2O2 was produced in PavCuAO4 transiently expressed tobacco leaves. The above results strongly proved that PavCuAO4 can decompose Put and may promote fruit ripening by increasing the content of ABA and H2O2 while suppressing total free PA levels in the fruit.

Calcium decreases cell wall swelling in sweet cherry fruit

Swelling of epidermal cell walls decreases cell-to-cell adhesion and increases cracking susceptibility in sweet cherry. Ca is suggested to decrease cracking susceptibility by crosslinking of cell wall components and, possibly, by decreasing swelling. The objective is to test this hypothesis. The effect of Ca on swelling of anticlinal epidermal cell walls was quantified microscopically in vivo using excised skin sections and in vitro using extracted cell walls. After removal of turgor, cell wall thickness increased. Incubation in CaCl2 decreased cell wall thickness up to 3 mM CaCl2. At higher concentrations thickness remained constant. Decreased cell wall swelling in vivo also occurred with other salts of divalent and trivalent cations, but not with those of monovalent cations. Decreased swelling was due to the Ca cation, the anions had no effect. Ca also decreased swelling of cell walls that were already swollen. CaCl2 also decreased swelling of extracted cell walls in vitro. There was no effect on swelling pressure. The effect on swelling increased as the CaCl2 concentration increased. Chlorides of divalent and trivalent cations, but not those of monovalent cations decreased swelling in vitro. The decrease in swelling among the divalent cations was linearly related to the radius of the cation. The results indicate that Ca decreases cracking susceptibility by decreasing swelling.

Sweet cherry yield, fruit quality and water productivity under rainfed conditions in eastern Free State

Sweet cherry yield, fruit quality and water productivity under rainfed conditions in eastern Free State

Characterization and fungicide sensitivity of Colletotrichum godetiae causing sweet cherry fruit anthracnose in Guizhou, China.

Sweet cherry is an important fruit crop with high economic and ornamental value in China. However, cherry fruit anthracnose, caused by Colletotrichum species, greatly impacts cherry yield and quality. Here, we surveyed cherry anthracnose in Guizhou, China from 2019–2020. Necrotic sweet cherry fruits were collected from different areas in Guizhou and examined. A total of 116 Colletotrichum strains were isolated from these symptomatic fruits. Based on the morphological characteristics of the isolates and phylogenetic analyses of concatenate internal transcribed spacer (ITS) region and ACT, CHS-1, GAPDH, TUB2, and HIS3 genes, the pathogen responsible for causing sweet cherry anthracnose was identified as Colletotrichum godetiae. Pathogenicity tests were conducted by inoculating healthy sweet cherry fruits with spore suspensions of the fungal pathogen, and Koch’s postulates were confirmed by pathogen re-isolation and identification. The Q-1 isolate showed different sensitivities to 13 fungicides, exhibiting seven different modes of action, and its EC50 values ranged from 0.04 to 91.26 μg ml−1. According to that, the sensitivity of 20 isolates from different samples to ten fungicides with better performance, were measured. The results showed that 6 of the 10 fungicides (difenoconazole, propiconazole, prochloraz-manganese, pyraclostrobin, trifloxystrobin-tebuconazole, and difenoconazole-azoxystrobin) all showed higher sensitive to the 20\°C. godetiae isolates, and no resistance groups appeared. Its EC50 values ranged from 0.013 to 1.563 μg ml−1. In summary, this is the first report demonstrating that C. godetiae causes sweet cherry anthracnose and the results of this study provide insights into how sweet cherry anthracnose could be effectively controlled in China.

Screening of cherry leaf roll virus in Sambucus nigra plants in Ukraine

Goal. Cherry leaf roll virus (CLRV) infects naturally a wide range of herbaceous and woody plants, different species of trees, shrubs, horticultural, ornamental, weed plants and causes significant economic losses in many hosts and countries. CLRV on elderberry species was reported in Europe, USA, Iran and North America. Recently this virus has been detected in sour and sweet cherry fruit orchards in Ukraine. Testing of other hosts than Prunus was performed in Ukraine only recently. The aim of the study was to test the black elderberry plants (Sambucus nigra L.). for the presence of CLRV in the Poltava region and Kyiv regions.&#x0D; Methods. Sampling was carried out in the summer–autumn period in 2019—2021 in the territories of the Poltava and Kyiv regions and in Kyiv city. Samples of healthy elderberry plants were also analyzed. Visual diagnostics, enzyme-linked immunosorbent assay in DAS-ELISA modification, total RNA extraction, RT-PCR with primers for a 412 bp fragment of the 3’ untranslated region of the CLRV genome, and statistical data analysis were used in this research. PCR products were separated on an 1.5% agarose gel. Commercial CLRV preparations were used for positive controls in DAS-ELISA.&#x0D; Results. Thirty three elderberry samples with symptoms of leaf rolling and mosaics of varying degrees were selected in the territory of the Poltava and Kyiv regions and in Kyiv city in 2019 and 2021 and used in the study. ELISA and RT-PCR results showed that 82% of the tested black elderberry samples were infected by CLRV.&#x0D; Conclusions. The presence of CLRV, its harmfulness for elderberry plants, and Sambucus potential to serve as a reservoir for the virus indicate the necessity of testing a wider range of plant species for сherry leaf roll virus in Ukraine.

Abscisic acid-responsive transcription factors PavDof2/6/15 mediate fruit softening in sweet cherry.

Softening is a key step during fruit ripening that is modulated by the interplay between multiple phytohormones. The antagonistic action of abscisic acid (ABA) and auxin determines the rate of fruit ripening and softening. However, the transcription factors that integrate ABA and auxin signals to regulate fruit softening remain to be determined. In this study, we identified several DNA-binding with One Finger (Dof) transcription factors essential for ABA-promoted fruit softening, based on transcriptome analysis of two sweet cherry (Prunus avium L.) varieties with different fruit firmness. We show that PavDof6 directly binds to the promoters of genes encoding cell wall-modifying enzymes to activate their transcription, while PavDof2/15 directly repress their transcription. Transient overexpression of PavDof6 and PavDof2/15 in sweet cherry fruits resulted in precocious and delayed softening, respectively. In addition, we show that the auxin response factor PavARF8, the expression of whose encoding gene is repressed by ABA, activates PavDof2/15 transcription. Furthermore, PavDof2/6/15 and PavARF8 directly bind to the 9-cis-epoxycarotenoid dioxygenase 1 (PavNCED1) promoter and regulate its expression, forming a feedback mechanism for ABA-mediated fruit softening. These findings unveil the physiological framework of fruit softening and establish a direct functional link between the ABA-PavARF8-PavDofs module and cell-wall-modifying genes in mediating fruit softening.

The role of gene duplication in the divergence of the sweet cherry

Gene duplication is a drive for genetic complexity and diversity, and can occur by several mechanisms. The plant phenotypic evolution is assumed to have been aided by whole-genome duplication. WGD (Whole genome duplication) events are often separated by tens of millions of years, resulting in a lack of a constant supply of variations for adaptation to ever-changing environments. Sweet cherry is a major Rosaceae fruit crop, however, it's uncertain whether distinct forms of gene duplications throughout evolution in sweet cherry where whole genome has been duplicated. In this study, genes were identified that derived from transposed, tandem, whole-genome, dispersed and proximal duplication events and differ in abundance, selection pressures, uninterrupted genes, expression divergence, as well as Go ontology enrichment analysis, and duplicate gene evolution were investigated using integrated large-scale genome and transcriptome datasets. The proximal and tandem mode of duplication expressed extreme conserve expression along with slow divergence, while transposed genes show higher regulatory divergence expression than other modes of duplication. We also examined at the development and expansion of gene families involved in the sugar metabolism pathways and organic acid, which are associated to the flavour and quality of sweet cherry fruit. The current study provides knowledge on the evolutionary fate and consequences of duplicate genes, providing the groundwork for future research into the dynamic evolution of duplicate genes.

The Influence of Fruit Size on Quality Attributes and Bioactive Compounds of Sweet Cherry Fruit

The Influence of Fruit Size on Quality Attributes and Bioactive Compounds of Sweet Cherry Fruit

The role of mucilage of Opuntia ficus-indica Mill. on sweet cherry fruit during storage

The role of mucilage of <i>Opuntia ficus-indica</i> Mill. on sweet cherry fruit during storage

Tissue-specific transcriptional analysis outlines calcium-induced core metabolic changes in sweet cherry fruit

The role of calcium in fruit ripening has been established, however knowledge regarding the molecular analysis at fruit tissue-level is still lacking. To address this, we examined the impact of foliar-applied calcium (0.5% CaCl2) in the ripening metabolism in skin and flesh tissues of the sweet cherry ‘Tragana Edessis’ fruit at the harvest stage. Exogenously applied calcium increased endogenous calcium level in flesh tissue and reduced fruit respiration rate and cracking traits. Fruit metabolomic along with transcriptomic analysis unraveled common and tissue-specific metabolic pathways associated with calcium feeding. Treatment with calcium diminished several alcohols (arabitol, sorbitol), sugars (fructose, maltose), acids (glyceric acid, threonic acid) and increased ribose and proline in both fruit tissues. Moreover, numerous primary metabolites, such as proline and galacturonic acid, were differentially accumulated in calcium-exposed tissues. Calcium-affected genes that involved in ubiquitin/ubl conjugation and cell wall biogenesis/degradation were differentially expressed between skin and flesh samples. Notably, skin and flesh tissues shared common calcium-responsive genes and exhibited substantial similarity in their expression patterns. In both tissues, calcium activated gene expression, most strongly those involved in plant-pathogen interaction, plant hormone signaling and MAPK signaling pathway, thus affecting related metabolic processes. By contrast, calcium depressed the expression of genes related to TCA cycle, oxidative phosphorylation, and starch/sucrose metabolism in both tissues. This work established both calcium-driven common and specialized metabolic suites in skin and flesh cherry tissues, demonstrating the utility of this approach to characterize fundamental aspects of calcium in fruit physiology.

Assessment of the influence of weather factors on the quantitative indicators of sweet cherry fruits by Ridge regression

Sweet cherries are a favourite stone crop among consumers of fruit products. At present, the demand for sweet cherries is growing, which encourages the expansion of the varietal range of crops with different ripening periods. The purpose of this study was to develop a mathematical model for predicting the formation of fruit and sweet cherry pyrene mass depending on weather factors and varietal characteristics. The study was conducted during 2008–2019 in the conditions of the Southern Steppe zone of Ukraine on 33 varieties of sweet cherries of early, medium, and late ripening periods. The average mass of the sweet cherry fruit over the years of research was 8.41 g, and the average mass of the pyrene was 0.56 g. Late-ripening sweet cherry varieties had the best fruit mass (7.27–12.18 g). According to the maximum average mass of the fruit, the varieties Kazka, Dilema, and Kosmichna were distinguished. Sweet Erlise, Pervistok, Melitopol black and Krupnoplidna varieties had the lowest pyrene mass in sweet cherry fruits. In the group of early ripening, the best ratio of pyrene to fruit pulp was found in the Kazka variety, in medium-ripening varieties – Cordia, Perviystok, and Orion, in late-ripening varieties – Udivitelna, Krupnoplidna, and Prazdnichna.The smallest variability in sweet cherry fruit mass in the group of early-ripening varieties was detected in Sweet Erlise, in mid-ripening – Temp, and in late-ripening – Regina, while in pyrene mass – Rubinova Rannia, Vynka and Regina, respectively. Weather conditions had a dominant influence on the formation of fruit mass for all sweet cherry varieties under study, and varietal characteristics had a dominant effect on pyrene mass. The maximum influence on the formation of sweet cherry fruit mass of early varieties was provided by the indicator – the number of days with precipitation in May exceeding 1 mm, and for medium and late ripening varieties – the average monthly amount of precipitation in June. Decisive importance for the formation of pyrene mass in sweet cherry fruits of early ripening varieties was the average monthly amount of precipitation in May, in the middle ripening period – the average monthly amount of precipitation in June, in the late ripening period – the number of days with precipitation exceeding 1 mm in May.

Xylogenesis and phloemogenesis in the flesh of sweet cherry fruit are limited to early-stage development

Water inflows into sweet cherry fruit occur via the xylem and the phloem vasculatures of the pedicel. The rates of these inflows are subject to marked changes during fruit development. The objective was to establish if, and when, xylogenesis and phloemogenesis occur in the fruit flesh (mesocarp) during fruit development. Fruit were cut in half and the median and the lateral bundles inspected by light microscopy. Fruit mass increased with time in a double sigmoid pattern. Xylogenesis and phloemogenesis were both limited to early fruit development (stage I). There were no consistent changes in the areas of either xylem or phloem after stage I until maturity (i.e., during stages II and III). The cross-sectional areas of xylem and of phloem in a bundle were both linearly related to total bundle area. Most of the increases (stage I) in bundle area (62%, r2 = 0.99***) were accounted for by increases in phloem area and about 35% (r2 = 0.97***) by increases in xylem area. A small percentage of the xylem area increase (about 4% of the total area of the bundle; r2 = 0.48***) was contributed by the appearance of intercellular spaces within the xylem. Our results suggest, that new xylem and phloem tissues are differentiated only during early development.

Studies of the impact of environmental conditions and varietal features of sweet cherry on the accumulation of vitamin C in fruits by using the regression analysis method

The accumulation of vitamin C in sweet cherry fruits depends on the variety and environmental conditions. The aim of our research was to substantiate the rate of impact of weather factors as well as of varietal features on vitamin C accumulation in sweet cherry fruits. The varieties ʹKazkaʹ and ʹZabutaʹ, ʹKordiaʹ and ʹMirazhʹ were chosen as the best ones from among 33 varieties of early, medium and late term of ripening (7.31–10.67 mg 100 g-1) according to the average content of vitamin C in sweet cherry fruits. The studies found that the environmental conditions of the research years had the largest impact on the vitamin C content in the fruits of late and early ripening varieties, and in the fruits of medium ripening variety the vitamin C amount depended on the varietal features. The practicability of forecasting of vitamin C content in sweet cherry fruits on the average indices for a group of early and late maturity varieties, but not separately for every pomological variety, has been proven. For the medium ripening variety this index can be forecasted within each pomological variety. The models of dependence of vitamins C accumulation on the impact of meteorological parameters were evaluated on the basis of the principle components analysis and the least square method.