Sweet Cherry Cultivars Research Articles

Regulation of crop load and quality in sweet cherry cv. ‘Sweet Heart’ using blossom thinning

ABSTRACT Self-fertile cultivars of sweet cherry (Prunus avium) produce heavy crop load that is often associated with small and poor-quality fruits. Therefore, a crop load-management strategy is required to improve the quality of the fruit. In this study, the effect of blossom thinners on fruit set, yield and quality of the fruits was evaluated. Three types of blossom thinners were used at three different concentrations viz., ammonium thiosulphate (ATS) (1, 1.5 and 2%), naphthaleneacetic acid (NAA) (20, 40 and 60 ppm) and corn oil emulsion (1, 2 and 3%). These were sprayed at 80% of the bloom stage. The vegetative, flowering, fruit set and yield parameters were observed and recorded. Fruit quality was evaluated by measuring the physical and chemical characteristics of the fruits at the harvest stage. Negative correlation was found between fruit set and quality of fruit. The reduction in the crop load was associated with enhanced vegetative growth, including higher leaf:fruit ratio, higher supply and availability of photosynthates to the remaining fruitlets and reduced fruit firmness and titratable acidity. Fruit size, weight, volume, hue value, chroma value, soluble solid content (SSC), total sugars, SSC/acid ratio, anthocyanin and ascorbic acid content were enhanced as a result of thinning. The foliar spray of ATS at 2% and NAA at 60 ppm, at 80% bloom proved to be the most effective in reducing crop load and enhancing the fruit quality.

Optimizing Sweet Cherry Attributes through Magnesium and Potassium Fertilization

Plant nutrition through fertilizer application plays a crucial role in enhancing crop quality and yield, necessitating a balanced fertilization approach. Sweet cherry, esteemed as one of the most prized crops worldwide, was the focus of this three-year study spanning from 2019 to 2021, involving the sweet cherry cultivar Burlat. This study investigated the foliar application of magnesium (Mg) and potassium (K) to enhance fruit quality parameters. Different doses of Mg (250 g hL−1 and 125 g hL−1) and K (100 g hL−1 and 50 g hL−1) and a control treatment were administered to sweet cherry trees to assess their impact on fruit quality. At the commercial ripening stage, fruits from each treatment were harvested for comprehensive evaluation, including biometric and chromatic parameters, fruit firmness, routine parameters, sensory profile, and nutrient content analysis. Results from the study revealed notable enhancements in fruit weight and dimensions, particularly in the control treatment in 2020. Furthermore, Mg125 and Mg250 treatments exhibited improved color development and accelerated maturity by increasing the total soluble solids content while decreasing titratable acidity. Sensorial profiling indicated that Mg125 and Mg250 treatments intensified color intensity and sweet taste while mitigating sour taste perceptions. Conversely, potassium fertilization, especially the K50 treatment, led to increased fruit firmness and nutrient content. These findings offer valuable insights into optimizing sweet cherry production practices globally.

First Report of Pseudomonas amygdali pv. morsprunorum causing Bacterial Canker in Sweet Cherry Orchards in Washington State.

In 2023, an outbreak of bacterial canker disease (BCD) in sweet cherry orchards caused significant economic losses to growers and nurseries in the Pacific Northwest, USA (Fig. S1). The cherry industry in Washington State alone is valued at over $800 million (USDA NASS, 2022). BCD poses a recurring threat to the state's sweet cherry [Prunus avium (L.) L.] orchards, especially young and newly planted orchards. Three Pseudomonas species, including P. syringae pv. syringae (Pss), P. amygdali pv. morsprunorum (Pam) (formerly P. syringae pv. morsprunorum Race 1, Psm1), and P. avellanae pv. morsprunorum (formerly P. syringae pv. morsprunorum Race 2, Psm2), have been reported to be associated with BCD in sweet cherries (Hulin et al. 2019). While Pss is widely prevalent in the United States, Pam has only been reported in Michigan (Renick et al., 2008) as well as in Europe, Central America, South Africa and Australia (Hulin et al. 2019) . In 2023, we surveyed more than 60 cherry orchards and collected hundreds of canker samples from newly planted up to 8-year-old trees. BCD prevalence ranged from 40-100% in cherry orchards, leading to the removal of hundreds of thousands of trees. Affected cherry trees exhibited characteristic bacterial canker symptoms, including dead bud, canker, and gummosis (Fig. S1). Bacteria were isolated from canker tissues or ooze on King's B (KB) agar plates (King et al., 1954) and more than 300 fluorescent Pseudomonas isolates were obtained from 12 symptomatic sweet cherry cultivars. PCR results using Pss- and Pam- specific primers (SyrB and Psm1, Table S1) (Sorensen et al., 1998; Kałużna et al., 2016) revealed that 91.9% and 8% isolates were tested positive for SyrB and Psm1, indicating that these isolates potentially belong to Pss and Pam, respectively. Pathogenicity tests using immature cherries cv. Sentina showed that all isolates caused typical necrotic lesions and could be re-isolated and re-identified as Pss and Pam, thus completing Koch's postulates. The identity of three Pam representative isolates (S79, S158, S202) was further confirmed by comparing gyrD and rpoD housekeeping genes as well as 16S rRNA gene sequence with other Pam strains in GenBank (Parkinson et al., 2010; Gomila et al., 2017). Blast searches against GenBank using gyrB (GenBank accession numbers PP357444-PP357446), rpoD (PP357447-PP357449) and 16S rRNA (GenBank accession numbers PP421223-PP421225) gene sequences, ranging from 520 to 859bp, matched those of the Pam isolates (GenBank accession numbers CP026558 or PP218075) with 100% homology and 100% query coverage, further indicating that these isolates are indeed Pam. This represents the first documented record of Pam causing BCD in the Pacific Northwest, USA, suggesting the complexity of the disease, which underscores the need for effective management strategies for cherry growers in the region.

Effects of Ripening Phase and Cultivar under Sustainable Management on Fruit Quality and Antioxidants of Sweet Cherry

Sweet cherry grown under sustainable management produces highly valuable fruits, whose quality shows important biochemical and morphological changes during ripening. Research was carried out in Iasi (Romania), with the aim to assess the quality characteristics of the sweet cherry fruits of three cultivars (Van, Andreiaș, Margonia), grown in an inner or outer position inside the tree crown, at the pre-ripening or full ripeness phase. In 2022, the colour component a* showed higher values in cv. Van and Andreias red fruits and in an inner position, whereas the components L* and b* at the full ripeness phase were highest in cv. Margonia. The dry matter and total soluble solids contents increased from the pre-ripening to the full ripeness phase and were highest in cv. Van sweet cherry fruits; the DM of fruit from the outer part of crown was higher than that of fruit from the inner part at the pre-ripening phase. The content of phenolics was the highest in cv. Margonia fruits at the pre-ripening stage and in cv. Van at the full ripeness phase and higher in the inner tree crown zones. The cultivar Margonia generally showed the highest vitamin C content in both years and development phases. The yellow fruit cv. Margonia mostly showed the highest values of chlorophyll a and b. The fruit’s content of carotene, lycopene, and anthocyanins was generally the highest in the red fruits of cv. Andreias. The examined sweet cherry cultivars showed a high variability in fruit nutritional quality and proved to be a rich source of bioactive compounds with antioxidant potential.

Sweet Cherry Plants Prioritize Their Response to Cope with Summer Drought, Overshadowing the Defense Response to Pseudomonas syringae pv. syringae.

Disease severity and drought due to climate change present significant challenges to orchard productivity. This study examines the effects of spring inoculation with Pseudomonas syringae pv. syringae (Pss) on sweet cherry plants, cvs. Bing and Santina with varying defense responses, assessing plant growth, physiological variables (water potential, gas exchange, and plant hydraulic conductance), and the levels of abscisic acid (ABA) and salicylic acid (SA) under two summer irrigation levels. Pss inoculation elicited a more pronounced response in 'Santina' compared to 'Bing' at 14 days post-inoculation (dpi), and those plants inoculated with Pss exhibited a slower leaf growth and reduced transpiration compared to control plants during 60 dpi. During differential irrigations, leaf area was reduced 14% and 44% in Pss inoculated plants of 'Bing' and 'Santina' respectively, under well-watered (WW) conditions, without changes in plant water status or gas exchange. Conversely, water-deficit (WD) conditions led to gas exchange limitations and a 43% decrease in plant biomass compared to that under WW conditions, with no differences between inoculation treatments. ABA levels were lower under WW than under WD at 90 dpi, while SA levels were significantly higher in Pss-inoculated plants under WW conditions. These findings underscore the influence on plant growth during summer in sweet cherry cultivars that showed a differential response to Pss inoculations and how the relationship between ABA and SA changes in plant drought level responses.

Effect of preharvest biofilm application regimes on cracking and fruit quality traits in ‘0900 Ziraat’ sweet cherry cultivar

BackgroundFruit cracking impacts the quality of sweet cherry, significantly affecting its marketability due to increased susceptibility to injury, aesthetic flaws, and susceptibility to pathogens. The effect of 1% biofilm (Parka™) application regimes on fruit cracking and other quality parameters in the ‘0900 Ziraat’ cherry cultivar was investigated in this study. Fruit sprayed with water were served as control (U1). Fruit treated only once with biofilm three, two and one week before the commercial harvest were considered as U2, U3 and U4, respectively. Fruit treated with biofilm three, two, and one week before harvest were considered as U5; three and two week before harvest as U6; two and one week before harvest as U7; and fruit treated three and one week before harvest as U8.ResultsIn both measurement periods, the lower cracking index was obtained in biofilm-treated sweet cherry fruit. However, the firmness of biofilm-treated fruit was higher than that of the control fruit. The lowest respiration rate was observed in U7, while the highest weight was recorded in U4 and U5 than the control. The biofilm application decreased fruit coloration. The biofilm application also increased the soluble solids content of the fruit. The U2, U3 and U4 applications at harvest showed higher titratable acidity than the control. In both measurement periods, the vitamin C content of the U2, U5, U6, U7 and U8 applications was found to be higher than that of the control. The total monomeric anthocyanin of the U3 and U8 applications was higher than that of the control. Furthermore, the antioxidant activity of the U2, U3 and U5 in the DPPH, and the U7 and U8 in FRAP were measured higher thanthat of the control.ConclusionsThe application of biofilms has the potential to mitigate fruit cracking, prolong postharvest life of sweet cherries, and enhance fruit firmness.

Reduced Root Volume at Establishment, Canopy Growth and Fruit Production in ‘Lapins’/‘Colt’ and ‘Regina’/‘Gisela 12’ Sweet Cherry Trees

The success of establishing fruit orchards has traditionally been attributed to the vigor of the nursery plant used. This study aimed to evaluate the post-transplant survival, canopy growth and fruit productivity of two sweet cherry (Prunus avium L.) cultivars (‘Lapins’/‘Colt’ and ‘Regina’/‘Gisela 12’) with different radicular basal volumes of 100%, 50% and 25% and nursery plant types: (i) bare root (BR) or (ii) bagged (B). The initial stem diameter of the plants ranged from 12 to 19 mm, and their height ranged from 1.4 to 1.8 m. Plants grafted onto ‘Colt’ rootstock exhibited twice the initial root volume compared to those grafted onto ‘Gisela 12’. Evaluations were carried out in three commercial orchards during three seasons in the Central Valley of Chile. The results indicated that root volume and nursery type did not affect plant survival and productivity. For ‘Regina’/‘Gisela 12’, only the bag treatment resulted in less trunk cross-sectional area (TCSA) and shoot length, and for ‘Lapins’/‘Colt’, the BR25 treatment showed a lower initial TCSA than other treatments, although without a negative effect on yield. Hence, the presumption about the influence of root volume and plant type on the successful establishment of a sweet cherry on ‘Colt’ and ‘Gisela 12’ rootstock can be discarded. The survival, growth and precocity of the orchard depend more on post-planting conditions and water management than on the number or type of nursery plant roots. It is important to prioritize proper post-planting care and water management for optimal orchard health.

Sweet Cherry Fruit Firmness Evaluation Using Compression Distance Methods

Flesh firmness in sweet cherries is determined using the measurement of normalized deformation force, i.e., determining the required force for a distance equal to 5 or 10% of the diameter of the cherries per millimeter. However, a firmness method involving a defined distance is quite simple and suitable for easy applications. Hence, our study focuses on the impact of fruit physiology under various and fixed distances. To assess the firmness evaluation, two sweet cherry cultivars (Canada Giant and Regina) were selected and subjected to three different levels of compression distance equal to 1%, 5%, 10% of the fruit’s small thickness dimension along with a consistent compression distance of 0.16 mm. There was a strong correlation between panelists’ preferences and the fruit that had been subjected to both a 1% deformation force and a fixed distance of 0.16 mm within each cultivar. Physiological traits, membrane integrity, and the metabolome of the fruit in these categories were mostly unaffected by the control (0%), or 1%, deformation force, as shown by clustering and PCA analysis. The control and 1% deformation force groups showed similar patterns, contrary to those of the 5% and 10% deformation force groups. Given these considerations, a fixed distance of 0.16 mm and a minimal 1% deformation force possess the potential to be employed and implemented for monitoring the firmness of sweet cherries during postharvest preservation.

Synergistic approach of PCR-based fragment length analysis and amplicon deep sequencing reveals rich diversity of S-alleles in sweet cherries from the Caucasian region of origin.

The self-incompatibility system in sweet cherry (Prunus avium L.) prevents fertilization with own or genetically related pollen, and is genetically determined by the multi-allelic S-locus. Therefore, determining S-alleles is crucial for plant breeding and fruit production, as it enables the selection of compatible combinations of S-genotypes for successful pollination. In this study, S-alleles were identified in a total of 260 genotypes from the Caucasian region, the species' center of origin. S-allele genotyping was conducted using PCR fragment length analysis with the standard marker PaConsI-F/R2 and reference genotypes, complemented by sequence analysis through amplicon deep sequencing. The genotypes collected from Azerbaijan and Turkey exhibit a high allelic richness at the S-locus, particularly compared to modern sweet cherry cultivars worldwide. Nine previously undescribed S-alleles were identified and designated as S45, S46, S47, S48, S49, S50, S51, S52 and S53. Given the expected high diversity for other traits, this plant material represents a valuable resource for further breeding research and introgression of new traits in future breeding programs. Furthermore, our results underscore that fragment length alone may not be sufficient for unambiguous assignment of S-alleles due to minimal length differences between different alleles. To address this issue, an S-allele reference ladder was developed using the rich diversity for precise assignment of the S-alleles. This tool can be applied in future experiments as a robust and cost-effective method for accurate S-genotyping across different runs and laboratories. Additionally, several selected S-genotypes were planted in a trial field and will be maintained as an S-allele reference collection.

Effects of hot water treatments on the main physicochemical characteristics and the levels of vitamin C and polyphenols of two sweet cherry cultivars (Prunus avium L.) during cold storage and shelf-life

Effects of hot water treatments on the main physicochemical characteristics and the levels of vitamin C and polyphenols of two sweet cherry cultivars (Prunus avium L.) during cold storage and shelf-life

Determination and comparison of morpho-physiological characteristics of Turkish sweet cherry (Prunus avium L.) grown in Afyonkarahisar: local cultivars and genotypes

The research focused on analyzing qualitative and quantitative morpho-physiological characteristics of local sweet cherry cultivars and genotypes. Quantitative and qualitative characteristics (fruit weight, fruit length, fruit width, fruit shape, fruit pistil end, fruit suture, fruit skin colour, fruit flesh colour, length of fruit stalk, thickness of fruit stalk, weight of fruit stalk, colour of fruit juice, fruit juiciness, eating quality, fruit sweetness, stone weight, stone shape, TA, pH, L*, a*, b*, H, croma, cracking index, sensitivity class) with UPOV descriptors were used in the evaluation. The findings revealed a significant variation among local cultivars and genotypes. It was determined that there was a low-level negative correlation between cracking index and fruit weight, fruit length, stone weight, TA, pH and L*; and a low-level positive correlation between fruit width, fruit stem length, thickness and weight, SCC, a*, b*, H and croma. The heat map and clustering analysis classified local cultivars and genotypes into two main clusters, each containing several secondary sub-clusters. This classification indicates a significant potential within the characterized sweet cherry collection for targeted breeding purposes. In particular, local sweet cherry cultivars and genotypes classified into several clusters show promise as potential parental candidates for hybridization in breeding. As a result of the research, local cultivars and genotypes with high fruit weight and cracking resistance were identified. The dendrogram showing the examined characteristics visually expresses the differentiation between local cultivars and genotypes, thus indicating clear distinctions. We believe these genotypes can be employed in breeding and breeding research.

First report of canker caused by Cytospora sorbicola on Sweet Cherry (Prunus avium) in Chile.

Chile leads cherry exports in the southern hemisphere with a total of 415.315 t exported in the 2022 to 2023 season (IQonsulting, 2023). Cytospora canker, produced by Cytospora spp., causes destructive infections and limit the productivity of sweet cherry orchards (Luo et al. 2019). This study was focused on isolating Cytospora strains to identify and characterize the species present in sweet cherry. During the period 2019-2022, ten samples of stem or branch presenting canker, dieback, gummosis or dead buds, were collected from sweet cherry cultivars 'Skeena', 'Lapins', 'Santina', 'Sweetheart', and 'Regina', in the regions Ñuble and O'Higgins, Chile. Five mm pieces from the necrotic wood margins of the samples were rinsed with sterile deionized water, placed on potato dextrose agar (PDA, Difco) and incubated at 20±2 ºC for 5 days. One isolate was recovered from each sample, resulting in ten Cytospora-like strains. Single hyphal tips were transferred onto PDA plates and all isolates were deposited in the Chilean Collection of Microbial Genetic Resources (CChRGM). Colonies grown on PDA reached 89 mm in diameter in 10 d at 25 °C, showing irregular margin, lacking aerial mycelium, initially off-white to cream that turned greenish gray in the center, which darkens with age. After 20 days of culturing on pine needle agar (Chen et al. 2015), isolates produced conidiomata pycnidial, semi-immersed, black, and subglobose (362)445-555(681)×(357)528-700(1053) µm (n=10), generating amber slimy conidia masses; Conidiophores were phialidic, cylindrical, aseptate, hyaline (6.77)9-10.04(12.88)×(0.82)1.1-1.28(1.99) µm (n = 30); conidia were abundant, allantoid, hyaline to light brown, aseptate (3.39)4.28-4.57(5.36)×(0.69)0.96-1.09(1.47) µm (n = 30) (Supplementary Figure 1). No sexual morph was observed. With the exception of the strain RGM 3390, all the isolates shared morphological characters to the descriptions of Cytospora sorbicola Norphanph., Bulgakov, T. C. Wen & K. D. Hyde (Norphanphoun et al. 2017). Isolates were identified at species level, by sequencing DNA regions described by Pan et al. (2020): ITS1-5.8S-ITS2, LSU; act, tef-1α, and tub2 with the exception of the RBP2, because this region could not be amplified in seven out of ten isolates. The consensus tree included the concatenated sequences of the ten isolates and those of reference Cytospora species reported by Ilyukhin et al. (2023) using a maximum likelihood analysis with the tool IQ-TREE webserver. MLSA confirmed the taxonomic affiliation of nine of the isolates with C. sorbicola and one isolate with Cytospora sp. (RGM 3390), that might represent a novel species (Supplementary Figure 2). The isolates RGM 3399 and RGM 3400, were selected randomly for pathogenicity tests. Inoculations were performed on 2-year-old sweet cherry cv. 'Lapins' grow in pots in a greenhouse at 26±6°C. Seven plants per isolate were cut to about 6-cm length from the main stem, and inoculated onto fresh cuts with 5-mm mycelium PDA plugs of 5-d-old culture and wrapped in moist sterile cotton and parafilm to keep moisture. Six plants were inoculated with non-colonized PDA agar plugs as control. The average canker length 3 months after inoculation was 3.1 and 0.8 cm, for RGM 3389 and RGM 3400, respectively (Supplementary Figure 1). Symptomatic twigs were incubated in moist chambers at 20±2 ºC for 10 d, resulting in the re-isolation of Cytospora strains that produced pycnidia and conidia structures in agreement with C. sorbicola. Both strains were reidentified to fulfill Koch's postulates, control twigs remained asymptomatic and no fungus was isolated from these twigs. This is the first report of C. sorbicola causing canker on sweet cherry in Chile. Our findings suggest that this species could be the most recurrent in cherry in central Chile, coinciding with it found in California where C. sorbicola has been described as the main causal agent of Cytospora canker of stone fruits in California (Lawrence et al. 2018).

Enhancing the Quality and Fruit Yield of Sweet Cherry (Prunus Avium) Cultivars by Foliar Application of Boron

Enhancing the Quality and Fruit Yield of Sweet Cherry (Prunus Avium) Cultivars by Foliar Application of Boron

Quality changes of two sweet cherry cultivars with different susceptibility to cracking during the storage

Quality changes of two sweet cherry cultivars with different susceptibility to cracking during the storage

First Report of Brown Rot Caused by Monilia yunnanensis on Sweet Cherry in China.

Chinese cherry industry has developed rapidly over the past few years, with the planting acreage continuously expanding, from Shandong province to Liaoning, Shaanxi, Hebei, Sichuan etc. Monilia spp. are the most important causal agents of brown rot of cherry, to date, M. fructicola, M. mumecola, and M. fructigena were reported to cause brown rot of cherry in China (Chen et al. 2013; Yin et al. 2014; Liu et al. 2012). In May 2023, fruit of sweet cherry cultivar 'Hongdeng' (Prunus avium L.) with symptoms resembling brown rot were collected from Tongchuan City, Shaanxi Province. Conidia on diseased tissues were spread on a water agar (WA, 1.5% agar and distilled water) medium and isolated with a glass needle under a professional single spore separation microscope (Wuhan Heipu Science and Technology Ltd., Wuhan, China). If no conidia were present, fruit pieces (5 × 5 mm) at the intersection of healthy and diseased tissues were surface sterilized with a sodium hypochlorite solution (1%) for 30 s and washed three times in sterilized water, followed by 75% ethanol for 30 s, then washed three times in sterilized water. After the tissue pieces were dried, they were placed on potato dextrose agar (PDA; 200 g of potato, 20 g of dextrose, and agar at 20 g/L) and incubated at 22 °C for about twenty days to produce spores and then single spore isolation was carried out. Thirty single-spore isolates were obtained and all were morphologically similar. The isolates produced white-gray colonies with even margins and concentric rings of sporogenous mycelium after 3 days incubation, and abundant black-colored stromata on the PDA medium after 15 days of incubation at 22°C. Conidia were one-celled, hyaline, ellipsoid to lemon shape (14.12 × 10.37 μm), with 1-2 germs which is similar to M. yunnanensis on peach. The genomic DNA of the isolates was extracted as described previously (Chi et al. 2009). The pathogen identity was confirmed by multiplex PCR which resulted in a 237bp amplicon, which is diagnostic of M. yunnanensis (Hu et al. 2011). Further sequencing of the internal transcribed spacer (ITS) region 1 and 2 and 5.8S gene (accession number: OR192774) indicated 100% identity with that of M. yunnanensis isolates (accession numbers: MW355895, ON024742). The average daily growth of mycelium on PDA at 22°C was 11.44 mm. Koch's postulates were fulfilled by inoculating 20 mature sweet cherry fruits of cv. 'Van' with mycelial plugs in a drilled hole. After 3 days of incubation at 22℃ in an airtight plastic tray with wet paper, the inoculated fruit developed typical brown rot symptoms. The developing spores on inoculated fruit were confirmed to be M. yunnanensis based on ITS sequence. All control fruit inoculated with a PDA plug remained healthy. M. yunnanensis was first reported as the causal agent of brown rot of peach in China (Hu et al. 2011). Later studies demonstrated that it is also pathogen on other fruits, e.g. hawthorn (Zhao et al. 2013), plum (Yin et al. 2015), apricot (Yin et al. 2017), apple, and pear in China (Zhu et al. 2016). To our knowledge, this is the first report of cherry brown fruit rot caused by M. yunnanensis, indicating the high risk of this species to cherry production, and effective strategies must be taken to prevent the possible control failure in practice.

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.

Putrescine Increases Frost Tolerance and Effectively Mitigates Sweet Cherry (Prunus avium L.) Cracking: A Study of Four Different Growing Cycles

Sweet cherry producers must deal with different climactic challenges annually, specifically the impact of spring frost and the inherent risk of fruit cracking. This susceptibility arises from the simultaneous occurrence of spring frost during the bloom stage or the sweet cherry cracking at vulnerable maturity stages in sweet cherry trees during persistent rainfall. Given the change in climatic patterns, the implementation of new strategies and innovative approaches becomes imperative to alleviate potential damage from these climatic adversities. This study aims to explore—for the first time—the effectiveness of preharvest putrescine applications during the flowering stage and ripening on-tree to increase tolerance in sweet cherry against adverse climatic events throughout its on-tree development and at the time of harvest. In this context, foliar applications of putrescine at concentrations of 1 and 10 mM were administered to distinct sweet cherry cultivars, namely, ‘Prime Giant’ and ‘Sweetheart’. Over the course of four growing seasons, our investigation focused on evaluating the influence of this natural elicitor on the frost resilience of flower buds during the preharvest period and its impact on reducing fruit cracking in these selected cultivars. In this sense, the overall malondialdehyde content exhibited a reduction in flower buds treated with putrescine, and the fruit set experienced an increase across the majority of evaluated growing seasons. On the other hand, the incidence of sweet cherry cracking in putrescine-treated sweet cherries showed a consistent reduction in all the studied growing seasons. Our results indicate that preharvest treatments with putrescine effectively alleviate the susceptibility of flower buds to spring frost and significantly diminish fruit cracking, thereby enhancing the overall tolerance to abiotic stress. Furthermore, we evaluated different quality parameters at the time of harvest, including fruit firmness, external color, total soluble solids, and total acidity. Generally, the observed changes in these parameters were delayed in putrescine-treated fruit as compared to the control batch or remained unaffected. For this reason, the implementation of preharvest treatments based on putrescine emerges as a valuable strategy for adapting to climate change and mitigating the impact of abiotic stress, potentially increasing sweet cherry production.

Occurrence and Characterization of Sclerotinia sclerotiorum Causing Fruit Rot on Sweet Cherry in Southern China.

Sweet cherry (Prunus avium L.) is widely planted in northern China due to its high economic value, and its cultivation has gradually spread south to warm regions. However, fruit rot, observed on the young fruits, poses a considerable threat to the development of sweet cherry. To determine the causal agent, morphological observation, molecular identification, and pathogenicity tests were performed on isolates obtained from diseased fruits. As a result, Sclerotinia sclerotiorum was identified as the pathogen. Pathogenicity tests on different sweet cherry cultivars indicated that 'Summit' was highly sensitive to S. sclerotiorum, whereas 'Hongmi' showed significant resistance. Besides sweet cherry, S. sclerotiorum could also infect other vegetable crops we tested, such as cowpea, soybean, tomato, and chili. Fungicide sensitivity and efficacy assays showed that both fludioxonil and pyraclostrobin can effectively inhibit the mycelial growth of S. sclerotiorum and decrease disease incidences on the young fruits of sweet cherry. Furthermore, genome sequencing resulted in a 37.8 Mb assembly of S. sclerotiorum strain ScSs1, showing abundant SNPs, InDels, and SVs with the genome of S. sclerotiorum reference strain 1980 UF-70. The above results provide an important basis for controlling the fruit rot of sweet cherry caused by S. sclerotiorum in China.

DINAMICA PROCESULUI DE FOTOSINTEZĂ LA UNELE SOIURI DE CIREȘ ÎN CONDIȚIILE CLIMATICE DE LA SCDP IAȘI

The purpose of this study was to evaluate the influence of climatic conditions in the photosynthesis process at three cultivars of sweet cherry (‘Van’, ‘Andreiaș’ and ‘Margonia’) from the Research Station for Fruit Growing (RSFG) Iași. The ecophysiological response of the sweet cherry tree species was determined by evaluating the influence of light intensity on photosynthesis, as well as by determining the content of photosynthetic and carotenoid pigments of the leaves in different phenological stages (66 BBCH, 75 BBCH and 89 BBCH). The content of pigments in the leaves was analyzed spectrophotometrically, being estimated by the value of the light absorption capacity of the acetonic extract of pigments (1%) in the visible spectrum at different wavelengths. The obtained results showed that the intensity of the photosynthesis process has maximum values in the fruit ripening phenophase, the content in photosynthetic pigments (chlorophyll a and b) registering maximum values of 14.28 µg/mL, at an average light intensity of 53,000 lux.

CALITATEA FRUCTELOR UNOR SOIURI DE CIREȘ ÎN RAPORT CU CERINŢELE CONSUMATORULUI

The fruit quality is a complex of characteristics and traits, such as: fruit size, the content of sugar, acids, flesh consistence and succulence, flavour, etc. The objective of this study was to analyze fruit quality of sweet cherry cultivars in correlation with consumer preferences. The study was carried out at Genetic and Breeding Department of Research Institute of Fruit Growing Pitesti, Romania on 13 Romanian genotypes (‘Daria’, ‘Maria’, ‘Radu’, ‘Izverna’, ‘Tentant’, ‘Colina’, ‘Superb’, ‘Rubin’, ‘Simbol’, ‘Severin’, ‘H 04-4-38’, ‘H 06-3-77’, ‘H 06-11-57’) and 11 foreign cultivars (‘Kordia’, ‘Regina’, ‘Sweetheart’, ‘Karina’, ‘Vanda’, ‘Hertfort’, ‘Areko’, ‘Lapins’, ‘Penny’, ‘Folfer’, ‘Bigarreau Burlat’), in 2021 and 2022 years. The following determinations were carried out: fruit size by weighing, flesh firmness with penetrometer non-destructive Qualitest, soluble solids content with digital refractometer and pH with Hanna HI 84532 minititrator, such as sensory evaluation of fruits using a scale from 1 (very low) to 9 (very good). The results showed that the foreign cultivars were superior to the Romanian genotypes from the point of view of the size and fruits quality. Thus, on foreign cvs., the average fruit weight was 9.31 g, while on Romanian ones of 8.39 g. The soluble solids content of fruits was higher on foreign cvs. compared to the Romanian ones (15,59% Brix respectively 14.75% Brix). On the other hand, after the sensory evaluation of the fruits, the total score was slightly higher for the Romanian genotypes (51.20) compared to the foreign ones (51.08). For Romanian consumers the most important characteristics when choosing the cherry fruits are: taste - which must be sweet or medium sweet; size - which must be large and very large; colour – red and dark red; firmness – firm and very firm fruits. These results could be useful to breeders for selection the cultivars as genitors in controlled hybridization, to farmers for correct selection of cultivars on establishing new orchards, and to the fruit market for fresh consumption.