Grapevine cultivation in a Mediterranean environment is significantly influenced by climate conditions, which determine vine growth characteristics and berry quality, resulting in financial losses for growers. To address these issues and meet the export standards of Flame Seedless grapes, integrated strategies were adopted, including plastic covering along with foliar applications of 24-epibrassinosteroids and gibberellic acid. A split-plot experiment was conducted in 2024 and 2025, testing two gibberellic acid (GA 3 ) regimes (one at 110 µL L −1 [ppm] applied at three stages and another at 20 µL L −1 applied at two stages), alongside various concentrations of foliar-applied brassinosteroid (BR) at 0, 0.5, 1.0, 1.5, and 2.0 µL L −1 . The results indicated that the application of GA 3 and/or 24-epibrassinosteroids significantly improved the quality of grape clusters and berries, including their chemical traits, color parameters, and the biochemical composition of grape leaves. Specifically, 20 µL L −1 GA 3 enhanced berry firmness, berry adherence strength, coloration, and optimized total soluble solids (TSS), sugar, and anthocyanin levels, while decreasing the number of small berries, weight loss %, and titratable acidity. Meanwhile, the combined treatment of GA 3 at 20 µL L −1 + BR at 2.0 µL L −1 treatment µL L −1 significantly increased cluster weight, cluster length, shoulder length, berry weight, berry diameter, berry force, berry firmness, CIRG, TSS, TSS/acidity ratio, total sugars, reducing sugars, and anthocyanin, while decreasing small berry incidence and acidity. The combination of GA 3 at 20 µL L −1 with BR at 2.0 µL L −1 yielded the most significant improvements in berry and cluster dimensions and color intensity, as well as in the oxidative burst and antioxidant defense enzymes of fresh grape leaves. Overall, the results highlight that BR can be used as a partial substitute for GA 3 under plastic covering as a promising tool to facilitate early harvest, improve grape bunch quality and berry quality, and reduce postharvest losses.

In the paper are presented the results of studying the agrobiological characteristics of some seedless cultivars from the Ampelographic collection of PI NIARAMV: 'Bessemeannyi V-6', 'Călina', 'Centennial seedless', 'Flame seedless', 'Kișmiș lucistâi', 'Mecita', 'Otilia', 'Perlette', 'Perlon' – V. vinifera L. cultivars and interspecific cultivars 'Himrod', 'Interlaken' and 'Romulus'. The phenological stages, fertility coefficients, productivity indices and winter hardiness were assessed, and the relationships among the main fertility components were examined through linear regression analysis. The investigated cultivars exhibited a wide range of berry maturity periods—from very early to late—together with variable levels of fertility and productivity indices. Several genotypes showed favorable agronomic traits, highlighting their potential value as genetic resources for seedless grape breeding programs.

Low temperature is a major abiotic stressor that limits the distribution of various fruit tree species worldwide. In this study, the effects of chitosan-salicylic acid nanocomposite (CS-SA NCs) treatment were evaluated on antioxidant enzyme activity, the antioxidant pool, and membrane stability indices in the grapevine cultivar ‘Flame seedless’ under cold stress conditions. Prolonged exposure to cold, compared to the control, led to a reduction in maximum fluorescence (Fm), variable fluorescence (Fv), the ratio of photochemical to non-photochemical use of light energy in photosystem II (Fv/F0), and the ratio of variable fluorescence to maximum fluorescence (Fv/Fm). Levels of chlorophylls, carotenoids, total soluble protein content, antioxidant enzyme activity, ascorbate, and glutathione activity significantly decreased with increasing cold stress duration. Electrolyte leakage, malondialdehyde, and hydrogen peroxide content increased by 75%, 60%, and 80%, respectively, after 16 hours of cold stress compared to the control. Nanocomposite treatment significantly enhanced antioxidant activity and stabilized membranes under cold stress by reducing electrolyte leakage and malondialdehyde release. Overall, CS-SA NCs act as a biological stimulant and can be effectively used to improve the physiological and biochemical responses of grapevines under cold stress. Further research is needed to gain a comparative understanding of various physiological responses, which will help guide the application of this nanocomposite in extension services and field production systems.

IntroductionHydrogen-rich water (HRW) plays a crucial role in regulating plant growth and development. However, its potential involvement in modulating photosynthetic pigments, chlorophyll fluorescence (ChlF) parameters, antioxidant enzyme activities, and fruit ripening in (Vitis vinifera L.) ‘Flame Seedless’ grapes grown in a greenhouse remain unclear.MethodsThis study aimed to investigate the effects of HRW irrigation at a concentration of 1.0 mg L-1 on chlorophyll pigments, ChlF parameters, enzymatic antioxidant activities, and fruit quality.ResultsHRW irrigation induced a significant increase in carotenoid (Car) content, which was observed only on the first day after irrigation. It also significantly enhanced chlorophyll a (Chl a) and chlorophyll b (Chl b) contents, as well as ChlF parameters such as maximum quantum efficiency of photosystem II (Fv/Fm), and the photochemical quantum yield of PSII (ΦPSII), while non-photochemical quenching (NPQ) decreased, indicating enhanced PSII functionality and photosynthetic performance. Antioxidant enzyme activities, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), were also enhanced, reducing reactive oxygen species (ROS) accumulation and maintaining ROS homeostasis in grapevine leaves. HRW treatment promoted the accumulation of secondary metabolites such as total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin content (TAC), and Car, which contributed to an improved color index of red grapes (CIRG). Additionally, fruit quality was improved by increasing total soluble solids (TSS), soluble sugars, and pH, while reducing fruit firmness and titratable acidity (TA). Berry weight and overall yield were also enhanced compared with control plants.DiscussionThese results demonstrate that HRW is a promising and sustainable approach for enhancing photosynthetic performance, antioxidant defense, secondary metabolite accumulation, and fruit quality in greenhouse-grown ‘Flame Seedless’ grapes, providing a practical basis for improving grape cultivation and production.

Abiotic stresses such as high temperature, humidity fluctuations, and excessive light negatively impact grapevine physiological functions, resulting in irregular vegetative growth and reduced productivity. Natural plant growth regulators and essential oils offer potential eco-friendly strategies to mitigate these adverse effects. This study investigated the effects of foliar applications of 24-epibrassinosteroid (Br) at concentrations of 1, 2, and 3 mg/L and jasmine oil (JO) at 500, 1,000, and 1,500 µL/L on Flame Seedless grapevines exposed to abiotic stress. The treatments aimed to enhance vegetative development, nutrient uptake, biochemical attributes, and yield. Results showed that all treatments successfully improved the vegetative growth of Flame Seedless grapevines by increasing leaf area, shoot length, diameter, number of leaves/shoots, pruning wood weight, internode length, and coefficient of wood ripening. They also improved the mineral content in leaf petioles, total carbohydrates in canes, chlorophyll contents in leaves, and yield per vine. In addition, the quality of the Flame Seedless grapevine was improved by increasing cluster weight, length, width, berry firmness, length, width, soluble solids content (SSC), titratable acidity (TA), SSC/TA ratio, total sugars, phenols, anthocyanin, and flavonoids, activities of peroxidase (POX), phenylalanine ammonialyase (PAL), polyphenoloxidase (PPO) and catalase (CAT) enzyme in berry. Application of Br at 3 mg/L yielded the highest significant values for vegetative growth parameters, yield, and physical characteristics. While JO at a rate of 1,500 µL/L increased the total phenols, flavonoids, and anthocyanin, as well as PPO, PAL, POX activity, and CAT in the berry. Foliar application of Br and JO effectively mitigated the adverse effects of abiotic stress in Flame Seedless grapevines.

Influence of Different Irrigation Levels on Anatomical Structure of Buds, Fertility, Productivity, and Fruit Quality of Flame Seedless Grapevines under Arid Climate Conditions

Photosynthetic characteristics are critical for grape growth and development. Drought conditions in arid regions significantly affect these characteristics. To identify grape varieties better suited for cultivation in arid environments, this study evaluated the leaf phenotypes and photosynthetic characteristics of 27 table grape varieties in Hotan Prefecture, China. Results revealed significant variations in leaf phenotypes and chlorophyll content (SPAD) among varieties under Hotan’s drought conditions. ‘Kyoho’ exhibited the largest leaf area (254.34 cm2), while ‘Munage’ had the smallest (112.43 cm2), and ‘Manaizi’ showed the highest chlorophyll content (SPAD = 44.21). ‘Munage’ and ‘Flame Seedless’ recorded the highest net photosynthetic rates (PNmax = 16.24 and 16.23 μmol·m−2·s−1, respectively), while ‘Thompson Seedless’ had the lowest respiratory loss (RD = 1.15 μmol·m−2·s−1) and light compensation point (Ic = 22.41 μmol·m−2·s−1), with a highly significant positive correlation between RD and Ic. ‘Crimson Seedless’ exhibited the highest light saturation point (Isat = 2745.15 μmol·m−2·s−1). Chlorophyll fluorescence analysis indicated that ‘Autumn Black’ had the highest PSII photochemical yield (Fv/Fm = 0.84), while ‘Zicuiwuhe’ showed high energy transfer indices (PIabs = 1.78, PItotal = 1.66) and electron transfer efficiency (φEo = 0.39). PIabs was significantly correlated with Fv/Fm, Fv/Fo, and energy flux parameters. ‘Molixiang’ demonstrated superior energy utilization, with the highest light absorption (ABS/CSm = 2440.8) and electron transfer flux (ETo/CSm = 874) and the lowest energy dissipation (DIo/CSm = 455.8), supported by a negative correlation between energy dissipation (DIo/CSm) and photochemical efficiency (φEo). Principal component analysis revealed that ‘Molixiang’ had the highest comprehensive photosynthetic adaptability score (0.97), followed by ‘Zicuiwuhe’ (0.79) and ‘Hetianhong’ (0.73), under Hotan’s drought stress conditions. These findings provide valuable insights for selecting and breeding grape varieties adapted to arid environments and climate change.

Effect of canopy management on yield and quality attributes of grafted “Flame Seedless” grapevines under overhead plastic covering and open field conditions

Background: Vitis vinifera L. exhibits diverse varietal traits influencing fruit quality and stress tolerance. The summer black grape (Xiahei), known for its superior tolerance to abiotic stress and intense pigmentation, was hypothesized to possess distinct metabolic and genetic profiles, particularly in flavonoid and anthocyanin biosynthesis. This study aimed to elucidate the metabolic and molecular basis underlying these phenotypic traits by comparing carbohydrate composition and metabolomic and transcriptomic profiles of four grape varieties (summer black, flame seedless, black grape, and red milk). Methods: Grapes were consistently sampled five days after full maturity, and metabolites were analyzed using UPLC-MS/MS and GC-MS, while transcriptome analysis employed RNA sequencing followed by qRT-PCR validation. Results: The results demonstrated that carbohydrate content was similar among all grape varieties, whereas the summer black grape showed significantly higher levels of flavonoids, particularly anthocyanins such as delphinidin-3-O-glucoside, cyanidin-3-O-glucoside, and pelargonidin-3-O-glucoside. Metabolomic analyses revealed substantial enrichment of metabolites involved in flavonoid biosynthesis pathways, in agreement with transcriptomic data showing significant upregulation of key regulatory genes (CHS, DFR, and ANS) specific to anthocyanin biosynthesis. These findings suggest that the pronounced anthocyanin accumulation in summer black grape contributes to its distinctive dark pigmentation and enhanced resistance to abiotic stresses compared to other varieties. Conclusion: This study provides novel insights into the molecular and metabolic mechanisms driving anthocyanin accumulation in summer black grapes, which could inform future breeding programs aimed at improving grape resilience.

Early grape maturation is an important trait for Egypt’s grape export program to meet international market demands on time. A plastic-covering technique along with exogenous brassinosteroids (BR) treatments was used on ‘Flame Seedless’ grapes, in a two-year experiment to assess fruit quality at harvest and during storage. The results indicated that vines protected by plastic cover benefit from early maturation irrespective of BR treatment, with a mean harvest time two weeks earlier than that of grapes grown without the cover. However, this also resulted in a decrease in grape anthocyanin content. The application of BRs could partly compensate for this insufficiency, concurrently enhancing the grapes’ qualitative attributes and storage potential. The upregulation of selected anthocyanin biosynthesis-related genes such as chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), and UDP-glucose-flavonoid 3-O-glucosyltransferase (UFGT)was confirmed to be in a linear and concentration-dependent relationship with BR treatments and associated with significantly increased anthocyanin content. Based on our research, it appears that the combined use of a plastic cover with elevated concentrations of brassinosteroids (0.8 ppm) is a potentially effective strategy for expediting the harvest season and preserving shelf life and the quality of grapes during cold storage.

Quality of ‘Flame Seedless’ Grapes as affected by Postharvest Treatment of Essential Oils

Field examination spanning two years (2022-2023) have been done in the vine region of Minia Governorate, West of Samalout Center, to investigates the effects of foliar application of different concentrations of macronutrients (NPK) and micronutrients (Zn, B, Fe) on vegetative growth, leaf pigment content, and nutritional status of Flame Seedless grapevines. Treatments included various levels of NPK or micronutrients alone, and their combinations applied three times during the growing season. Results showed that combined foliar sprays of macro and micro -nutreints significantly enhanced shoot length, leaf number, leaf area, cane thickness, and pruning wood weight compared to untreated controls. Leaf chlorophyll and carotenoid as well as nutritional analysis contents were also highest in vines receiving combined macro- and micronutrients, indicating improved nutrient uptake and metabolic activity. The optimal treatment was foliar spraying with 0.75% NPK plus 100 ppm Zn/B and 150 ppm Fe, which maximized vegetative vigor and leaf pigment content while ensuring better economic returns for growers under local conditions. This integrated nutrient management approach supports sustainable viticulture by balancing growth and quality in Flame Seedless grapevines.

Field examination spanning two years (2022-2023) have been done in the vine region of Minia Governorate, West of Samalout Center, to evaluated the effects of foliar application of different concentrations of macronutrients (NPK) and micronutrients (Zn, B, Fe), alone and in combination, on the yield and fruit quality of Flame Seedless grapevines. Treatments were applied thrice during the growing season, and results demonstrated that combined foliar sprays of macro and micronutrients significantly improved yield parameters such as berry set percentage, cluster number and weight, and overall yield per vine compared to untreated controls. The highest improvements in both yield and berry quality were achieved with the combined application of 1.0% NPK + 150 ppm Zn/B + 200 ppm Fe, followed closely by 0.75% NPK + 100 ppm Zn/B + 150 ppm Fe. These treatments also enhanced berry size, weight, chemical attributes including total soluble solids, TSS/TA, reducing sugars, and anthocyanin content and reduced shot berry percentage, as well as total acidity. The findings suggest that integrated foliar nutrient management optimizes both productivity and fruit quality in Flame Seedless grapevines under Minia field conditions.

Bud-Break Dormancy and Improve Productivity of ‘Flame Seedless’ Grapevines in Response to Some Plant Extracts

Determination of optimal sampling time of grape embryo rescue based on near infrared spectroscopy combined with machine learning

Grape peelability varieties meet the demand for convenience and hygiene and are popular Grape varieties with easy peelability meet consumer demands for convenience and hygiene, making them increasingly popular. Differences in grape peelability are likely associated with variations in cell wall polysaccharide composition in the pulp and skin. Twelve table grape varieties (‘Zaoheibao’, ‘Qiuhongbao’, ‘Summer Black’, ‘Black Balado’, ‘Jinghongbao’, ‘Lihongbao’, ‘Flame Seedless’, ‘Crimson Seedless’, ‘Wanheibao’, ‘Wuhecuibao’, ‘Thompson Seedless’ and ‘Hutai No. 8’) were selected to investigate skin-pulp adherence, skin cell morphology, and cell wall polysaccharide content during fruit development. The role of cell wall polysaccharides in peelability was evaluated by assessing skin-pulp adherencce, skin cell morphology, cell wall polysaccharide content, and activities of related degrading enzymes across developmental stages of different grape varieties. Results showed that skin-pulp adherencce decreased by 6.4%~52.4% during fruit development, with significant varietal differences. ‘Black Balado’ exhibited the highest adhesion, while ‘Flame Seedless’ had the lowest. Cluster analysis grouped ten Eurasian grape varieties into two categories. The first group, which was easier to skin, included ‘Flame Seedless’, ‘Thompson Seedless’, ‘Wuhecuibao’, ‘Zaoheibao’, ‘Wanheibao’, ‘Jinghongbao’, ‘Lihongbao’, ‘Qiuhongbao’ and ‘Wuhebai’. The second group, characterized by poor peelability, included ‘Black Balado’. Anatomical observations revealed that as fruit development progressed, intercellular adhesion weakened and pulp cell separation became more pronounced. As fruit developed, cell wall polysaccharide content (cell wall material, cellulose, hemicellulose, protopectin, chelator-soluble pectin, water soluble pectin) decreased, while the activities of related degrading enzymes (cellulase, β-glucosidase, xylanase, xyloglucan endotransglycosylase, β-mannanase, polygalacturonase, pectate lyase, pectin methyl esterase, β-galactosidase, α-L-arabinofuranosidase) gradually increased. Specifically, the cell wall material content of the cell walls decreased by 30.3% to 64.8% in the pulp and by 23.9% to 51.4% in the pericarp across different varieties. protopectin and chelator-soluble pectin showed the most significant declines. In ‘Flame Seedless’ peel, protopectin content decreased by 97.1%, from 2067 µg•g–1 FW at the expansion stage to 60 μg•g–1 FW at maturity, and by 93.9% in the pulp. Chelator-soluble pectin content decreased by 87.8% to 97.7% in the peel and by 73.7% to 94.6% in the pulp, depending on the variety. The activities of cellulase and β-glucosidase showed relatively moderate changes during fruit development. From the expansion to the ripening stage, xylanase activity increased by 0.37-2.55 times in the peel and 0.01-1.84 times in the pulp. Similarly, xyloglucan endotransglycosylase activity rose by 0.38-2.37 times in the peel and 0.42-2.33 times in the pulp, while polygalacturonase activity increased by 0.21-2.85 times in the peel and 0.58-2.43 times in the pulp. Pectate lyase activity increased from 16% to 43% before the veraison stage and from 1% to 11% afterward. During both the expansion-to-verasion and verasion-to-ripening stages, pectin methyl esterase activity increased by 0.69-1.07-fold in the peel and 0.29-1.53-fold in the pulp, while β-galactosidase activity increased by 0.21-0.55-fold in the peel and 0.05-1.02-fold in the pulp. α-L-arabinofuranosidase activity increased by 1% to 341% in the peel and by 85% to 365% in the pulp. This study found that the peelability of table grapes gradually decreased during fruit ripening and varied significantly among different varieties. Further analysis indicated that peelability was negatively correlated with cell wall polysaccharide content and positively correlated with the activity of related cell wall-degrading enzymes. This study provides a theoretical framework for understanding the physiological mechanisms underlying grape peelability.

The effect of salinity stress on ‘Flame Seedless’ and ‘Superior Seedless’ grapevines seedlings (Vitis vinifera L.) grown hydroponically under salinity stress conditions, as well as the effectiveness of inoculation with Arbuscular Mycorrhizae Fungi (AMF) in reducing the harmful effects of salinity stress were investigated during 2022 and 2023 seasons. The investigation was carried out under Laboratory conditions, whereas the temperature was fixed at 25 ± 3 and relative humidity at 80 ± 5, referenced nutrient solution adapted with grapevines needs was used. The obtained results confirmed that, all vegetative parameters, fresh and dry weight of shoot and root systems, eaves main pigments and mineral status of both cultivars were negatively affected by increasing the salinity level in the nutrient solution. However, inoculated the seedlings with AMF significantly reduced these harmful effects of both cultivars. During both experimental seasons, the response of Flame Seedless seedlings to AMF inoculations was more perspicuous rather than those of Superior Seedless seedlings, these findings were true in most studied traits.

Effect of Some Phosphate Fertilizer Sources and Phosphate Solubilizing Microorganisms on Yield and Quality of Flame Seedless Grapes

(1) Background: The variability and trend in harvest dates of table and Pisco grapes have been scarcely studied. This can be closely influenced by bioclimatic indices since they account for the interactions between climatic factors and vine phenology. Understanding the environmental factors influencing harvest timing has become increasingly critical to perform specific viticultural practices. (2) Methods: The aim of this research was to evaluate the influence of bioclimatic indices on variability and trend of harvest date from the 2002–2003 to 2017–2018 seasons in Flame Seedless, Thompson Seedless, Muscat of Alexandria, and Moscatel Rosada growing in Northern Chile. (3) Results: The harvest date of Flame Seedless advanced significantly with an increasing Growing Season Temperature (GST) (from 1 October to 31 December), while Thompson Seedless showed a significant advancement in harvest date with rising the Maximum Springtime Temperature Summation SONmax (from 1 September to 30 November) values. Similarly, the harvest date of Muscat of Alexandria was significantly earlier with higher Heliothermal Index (HI) (from 1 July to 31 January and from 1 August to 30 April) values, whereas Moscatel Rosada exhibited a significant advancement in harvest date as the GST (from 1 July to 31 December and from 1 July to 31 January) increased. The trend in the harvest date of Thompson Seedless was statistically significant, reaching a coefficient of determination of 0.42. (4) Conclusions: Understanding the influence of bioclimatic indices on harvest date in long-term periods is critical in the context of climatic variability since producers can make more informed decisions to optimize grape quality and maintain sustainability in production systems.

Attempts to Reduce the Harmful Effects of Salinity on the Growth and Productivity of the Flame Seedless Grapevines