Abstract
Protected grape cultivation develops rapidly because of huge economic benefits. However, adverse environmental conditions (insufficient sunlight, high temperature, etc.) in protected cultivation led to low-quality berries. This study aimed to evaluate the effects of berry thinning on the quality attributes of two table grape cultivars (Baoguang and Cuiguang) under linkage greenhouse conditions. Three treatments (L, light berry thinning; M, moderate berry thinning; H, heavy berry thinning) were compared with the control (C, no berry thinning). Berry thinning increased berry weight, total soluble solids (TSS), fructose, glucose, the ratio of TSS to titratable acidity (TA), anthocyanin contents, berry firmness, and mineral contents (Ca, Fe, Na, Mg). Conversely, TA and organic acid profiles were decreased by berry thinning. Cultivars showed significant effects on most of the berry quality parameters. The interaction of cultivars by berry-thinning treatments affected sugar and acid components, anthocyanin contents, and mineral elements.
Grapes with unique flavors are welcomed by consumers worldwide. World grape production is mainly used for wine, and table grapes play a leading role in the Chinese market (Wang et al. 2017). In recent years, protected grape cultivation has developed quickly owing to its high profits. However, there are lots of challenges (such as high temperature, high humidity, and diminished light) in protected cultivation, which leads to low-quality berries featured as mild flavor, low sweetness, and poor color. Given this, producing high-quality berries under protected conditions is our main goal.
At present, many agricultural practices (including thinning, defoliation, etc.) are used to improve berry quality in viticulture. (Aru et al. 2022; Intrigliolo et al. 2014; Xi et al. 2020). Thinning, mainly cluster thinning and berry thinning, is a common crop load practice used to ensure high-quality berries (Carmona-Jimenez et al. 2021; Han et al. 2019; Song et al. 2018). Although cluster thinning was labor-saving (Gil et al. 2013), berry thinning allowed the inner berries to get more sunlight and fresh air, which was beneficial to preventing a higher incidence of pests and diseases (Piernas et al. 2022). Thus, berry thinning tended to improve berry quality. In recent years, researchers have conducted some studies on the effect of berry thinning on fruit quality. The content of sugar, anthocyanins, and the mass of mature berries in ‘Cabernet Sauvignon’ were all significantly enhanced by berry thinning (Han et al. 2019). Besides, berry thinning improved sensory properties in Shine Muscat grape berries (Choi et al. 2021). Although some studies discuss the influence of berry thinning on quality parameters, they focus on the basic quality traits (cluster and berry size, TSS, TA, etc.) under field cultivation. Little is known about the sugar and acid profiles, texture, and mineral nutrients under protected cultivation.
Nowadays, minority grape cultivars are being valued and grown for meeting a differentiated position in the market. Baoguang and Cuiguang are promising cultivars with unique flavors and high yields in the fresh berry market. The cultivation areas of these two cultivars are increasing rapidly in northern China, especially in protected areas. Thus, two potential table grape cultivars (Baoguang and Cuiguang) were selected as experimental materials. This study aimed to assess the effect of berry thinning on the quality composition of two table grape cultivars under linkage greenhouse conditions. Our results provide a reference for quality improvement of table grapes in future cultivation.
Materials and Methods
Grapevine materials and growing conditions.
The study was conducted in an experimental vineyard located in Shigezhuang, Changli, Hebei province, China (39°45′12′′N, 119°12′23′′E, altitude 20 m above sea level), in 2020. The vineyard was sandy loam soil. The soil has a pH of 6.22; organic matter of 1.43%; and total N, P, and K of 0.44 g⋅kg−1, 0.56 g⋅kg−1, and 1.66 g⋅kg−1, respectively. The region is characterized by a typical sub-humid continental monsoon climate.
Two table cultivars (Baoguang and Cuiguang) were selected as experimental materials because of their potential productivity. Both cultivars originated from a hand-pollinated cross between Kyoho (Vitis vinifera × Vitis labrusca, 4×) and Zaoheibao (V. vinifera, 4×) conducted in May 2003. Baoguang (BG) and Cuiguang (CG) were seeded table grape cultivars with blue-black skin and high yield. BG is an early-ripening cultivar and CG is a medium-ripening cultivar. Own-rooted vines were planted in 2014 in the linkage greenhouse covered by polyvinylchloride film (90% light transmittance, 0.14 mm thick, 50% horizontal shrinkage, and 15% vertical shrinkage). They were trained to pergola system (an East-West row orientation) with a height of 2.0 m and spaced 0.8 × 5.0 m apart. Each vine was pruned to 14 to 16 bearing canes and only one cluster in each bearing cane was retained before inflorescence. Winter pruning was carried out leaving two-bud spurs per cane. Water, fertilization, and pest management were carried out according to generally recommended standards for the region.
Treatments and experimental design.
Berry thinning was carried out when grapes were pea-size, corresponding to stage E–L 31 (Coombe 1995). Berries were removed manually. The following four thinning treatments were evaluated (Fig. 1):
C, control (no berry thinning).
L, light berry thinning (15% of berries removed per cluster).
M, moderate berry thinning (30% of berries removed per cluster).
H, heavy berry thinning (50% of berries removed per cluster).
Visual appearance of ‘Baoguang’ and ‘Cuiguang’ for different berry-thinning intensities under linkage greenhouse conditions. BG = Baoguang; CG = Cuiguang; H = heavy berry thinning; M = moderate berry thinning; L = light berry thinning; C = control.
Citation: HortScience 58, 1; 10.21273/HORTSCI16952-22
Visual appearance of ‘Baoguang’ and ‘Cuiguang’ for different berry-thinning intensities under linkage greenhouse conditions. BG = Baoguang; CG = Cuiguang; H = heavy berry thinning; M = moderate berry thinning; L = light berry thinning; C = control.
Citation: HortScience 58, 1; 10.21273/HORTSCI16952-22
Visual appearance of ‘Baoguang’ and ‘Cuiguang’ for different berry-thinning intensities under linkage greenhouse conditions. BG = Baoguang; CG = Cuiguang; H = heavy berry thinning; M = moderate berry thinning; L = light berry thinning; C = control.
Citation: HortScience 58, 1; 10.21273/HORTSCI16952-22
The experimental design used was randomized blocks with three replications per treatment. Each replication consisted of five vines. Two vines were used as guard vines at end of each block. According to commercial harvest standards (seeds turned brown), BG and CG were harvested manually 100 and 120 d after anthesis, respectively. Ten random clusters from five vines were sampled from each replication. For each cluster, 12 berries were randomly sampled from the shoulder, middle, and tail. The fresh berries were used to determine berry weight and size, water content, and texture. The remaining berries were frozen immediately in liquid nitrogen and stored at −80 °C for subsequent analysis of sugars, acids, mineral elements, and so on.
Physical traits of clusters and berries.
Fifteen clusters and thirty berries were randomly sampled from each treatment. They were weighted with an electronic balance. Cluster length and width were measured using a ruler; berry length (vertical diameter) and width (horizontal diameter) were analyzed by a digital vernier caliper.
Basic physical and chemical characteristics.
Fifteen fresh berry weights (FW) were determined immediately after sampling. And then berries were dried to a constant weight (DW) in a drying oven at 60 °C. The formula (FW − DW)/FW was used to calculate the water content.
MW (449.2): The molecular weight of cyaniding-3-glucoside;
DF (4): The dilution factor.
ε (26900): The molar absorptivity of cyaniding-3-glucoside in 1% HCl-methanol solvent.
The total ACs (g⋅kg−1) were expressed as cyaniding-3-glucoside in fresh berry skin.
The juice was collected by squeezing 30 berries randomly selected from each treatment. TSS content in the juice was measured using a digital refractometer (PAL-1; Atago, Tokyo, Japan). TA was measured using an automatic titrator (TitroLine Easy; Schott Instruments, Mainz, Germany). TA (g⋅L−1) was assayed by titration with 0.1 M NaOH to pH 8.3. TA was expressed as the tartaric acid equivalent.
Sugar and acid profiles.
Sugars and acids were analyzed using high-performance liquid chromatography system (LC-10Avp; Shimadzu, Kyoto, Japan). Thirty berries were ground into powder in liquid nitrogen. The sample (1.0 g) was added to 10 mL of distilled water for sugar extraction. The sample (4.0 g) was added to 4 mL of distilled water for acid extraction. These solutions were extracted in an ultrasonic bath at 37 °C for 40 min. The extraction solution was cooled to room temperature followed by centrifugation at 10,000 gn for 10 min at 4 °C. The supernatant (1 mL) was filtered through a 0.22-μm syringe-driven filter unit (Millex-GP; Merck Millipore, Burlington, MA, USA).
The apHera™ NH2 column (250 mm × 5 mm; Supelco, Bellefonte, PA, USA) and Phenomenex Luna C18 column (250 mm × 5 mm, 5 μm; Phenomenex, Torrance, CA, USA) were used for sugar components and acid components, respectively. The columns were maintained at 30 °C. Sugar components and acid components were detected by a Shimadzu (Kyoto, Japan) RID-10A refractive index detector and a Shimadzu SPD-10Avp ultraviolet-Vis detector (210 nm). The mobile phase of sugars was 75% acetonitrile in water and flowed at a rate of 0.8 mL⋅min−1. The mobile phase of acids was KH2PO4 (18 mm, pH 2.1) and flowed at a rate of 0.8 mL⋅min−1. Sugar and acid amounts were determined using peak areas with external standards (fructose, glucose, sucrose, tartaric acid, malic acid, and citric acid) and expressed as g⋅kg−1.
Texture attributes.
Texture properties were evaluated by a texture profile analysis (TPA) test. Firmness, cohesiveness, springiness, and chewiness were determined by using a texture analyzer (CT3; Brookfield, Middleboro, MA, USA) with a 50.8-mm-diameter cylindrical probe (TA25/1000). The TPA test was performed at 2 mm/s for deformation of 25%. The trigger value was 0.05 N. Texture profiling involved compressing the test substance twice and quantifying the mechanical parameters from the recorded force-deformation curves (Rolle et al. 2011; Szczesniak 2002).
Mineral elements.
The plastic containers were used for storing and treating the samples to avoid metal contamination. Containers were treated with 5% nitric acid for 24 h and then washed twice with Milli-Q water. Thirty frozen berries were ground into powder in liquid nitrogen manually. Four grams of powder was digested in concentrated nitric acid (10 mL) with a microwave digestion system (Mars6; CEM, Matthews, NC, USA). The digested solution was heated at 240 °C to remove the excess acid. The preceding step stopped when the remaining solution was ∼1 mL. The remaining solution was filtered into a 50-mL volumetric flask with Milli-Q water. Elemental analyses were carried out on an optical emission spectrometer (Optima 8000; PerkinElmer, Waltham, MA, USA). The standard solution was diluted to five concentrations with Milli-Q water for the standard curve. The contents of mineral elements were calculated by standard curves.
Statistical analysis.
Statistical data were analyzed using the software SPSS Statistics 26.0 (IBM, Armonk, NY, USA). Mean comparisons were performed by two-way analysis of variance, followed by Duncan’s multiple comparison test at P < 0.05. Principal component analysis (PCA) was applied to all measured attributes via Origin software version 2021 (OriginLab Corporation, Northampton, MA, USA).
Results
Basic cluster and berry characteristics.
Cluster and berry characteristics were affected by berry density treatments (Table 1). As expected, heavier berry thinning obtained lower cluster mass. The cluster mass was significantly lower in L, M, and H compared with control vines. Similar results were found with the cluster length and cluster width. Heavier berry thinning tended to obtain bigger berries. To be specific, M and H significantly increased the berry weight and vertical diameter. H notably increased the horizontal diameter. Besides, these parameters (except vertical diameter) varied in cultivars. CG berries had a larger cluster length, while other parameters (cluster mass, cluster width, berry weight, horizontal diameter) were higher in BG. The interaction of factors (cultivars × berry thinning treatments) on cluster mass and cluster length was noticeable.
Impacts of different berry densities on cluster and berry characteristics recorded in Baoguang and Cuiguang under linkage greenhouse conditions.
Physical and chemical indexes.
Berry thinning did affect the physical and chemical indexes (Table 2). Water contents were lower in L, M, and H. M and H significantly increased the contents of total anthocyanins by 13.18% and 33.44%, respectively. The TSS was markedly increased in H, whereas no difference was found in the L and M. M and H treatments showed lower TA. Conversely, the ratio of TSS to TA was notably higher in M and H, which suggested that M and H produced sweeter berries. Cultivars also affected these parameters. Water content was higher in BG, whereas TSS and the ratio of TSS/TA were higher in CG. Besides, the interaction of factors (cultivars × berry-thinning treatments) has a significant effect on water content and total anthocyanins.
Impacts of different berry densities on physical and chemical indexes recorded in Baoguang and Cuiguang under linkage greenhouse conditions.
Sugar and acid components.
Cultivars, berry-thinning treatments, and their interaction exerted significant effects on most variables (Table 3). Heavier berry thinning tended to obtain higher fructose and glucose, but sucrose was not altered by the berry thinning treatments. Compared with sucrose, fructose and glucose were the main sugars and their ratio was close to 1. Consequently, the sum of the three sugars was higher in M and H. In contrast to sugar components, acid components presented a downward trend with an increase in berry thinning. The content of citric acid was much lower than that of tartaric acid and malic acid. So, tartaric acid and malic acid were the main acids. The L, M, and H significantly reduced the contents of tartaric acid and the sum of the three acids. The content of malic acid was lower in M and H and that of citric acid was lowest in H.
Impacts of different berry densities on sugar and acid components recorded in Baoguang and Cuiguang under linkage greenhouse conditions.
BG produced higher sucrose and tartaric acid, but other sugars and acids were significantly higher in CG. The interaction of cultivars by berry-thinning treatments exerted larger effects on acids than on sugars. All acid components were affected by the interaction of factors (cultivars × berry-thinning treatments), whereas only glucose and sucrose were influenced by that.
Texture indexes.
Texture indexes were affected by berry-thinning treatments (Table 4). Heavier berry thinning obtained higher firmness and lower cohesiveness. H increased firmness by 22.62% and decreased cohesiveness by 16.67%. Springiness was lowest in H and unaffected by L and M. Chewiness was unaffected by treatment. Besides, firmness was higher in CG than BG, whereas springiness was higher in BG than CG. The interaction of factors (cultivars × berry-thinning treatments) did not affect any texture index.
Impacts of different berry densities on texture indexes recorded in Baoguang and Cuiguang under linkage greenhouse conditions.
Mineral nutrients.
Berry thinning had significant effects on mineral elements (Table 5). K content was unaffected by treatment. M and H significantly increased contents of Ca (11.43% and 31.22%, respectively) and Na (25.26% and 43.35%, respectively). L, M, and H significantly increased contents of Fe by 32.64%, 34.49%, and 41.44%, respectively. Mg content was significantly increased by H (7.72%). Mineral elements were also affected in cultivars. Contents of Ca and Mg were greater in BG compared with CG, whereas contents of K and Fe were greater in CG compared with BG. The interaction of factors (cultivars × berry-thinning treatments) had a significant effect on Ca, Mg, and Na. The effect on the three elements decreased in turn.
Impacts of different berry densities on mineral concentration recorded in Baoguang and Cuiguang under linkage greenhouse conditions.
Principal component analysis.
We performed PCA on the 28 traits of two grape cultivars to provide us with an overview visualization in a reduced dimension (Fig. 2A and 2B). The first two PCs explained 85.31% of the total variation and successfully identify the influences of berry thinning on fruit quality composition.
PCA of fruit quality compositions of Baoguang and Cuiguang subjected to different berry-thinning intensities under linkage greenhouse conditions. Loadings plot (A) and scores plot (B). BG = Baoguang; CG = Cuiguang; C = control; L = light berry thinning; M = moderate berry thinning; H = heavy berry thinning; ClM = cluster mass; ClL = cluster length; ClW = cluster width; BeW = berry weight; VeD = vertical diameter; HoD = horizontal diameter; WaC = water content; ToA = total anthocyanins; TSS = total soluble solids; TA = titratable acidity; Fru = fructose; Glu = glucose; Suc = sucrose; SumS = sum of the three sugars; Tar = tartaric acid; Mal = malic acid; Cit = citric acid; SumA = sum of the three acids; Fir = firmness; Coh = cohesiveness; Spr = springiness; Che = chewiness.
Citation: HortScience 58, 1; 10.21273/HORTSCI16952-22
PCA of fruit quality compositions of Baoguang and Cuiguang subjected to different berry-thinning intensities under linkage greenhouse conditions. Loadings plot (A) and scores plot (B). BG = Baoguang; CG = Cuiguang; C = control; L = light berry thinning; M = moderate berry thinning; H = heavy berry thinning; ClM = cluster mass; ClL = cluster length; ClW = cluster width; BeW = berry weight; VeD = vertical diameter; HoD = horizontal diameter; WaC = water content; ToA = total anthocyanins; TSS = total soluble solids; TA = titratable acidity; Fru = fructose; Glu = glucose; Suc = sucrose; SumS = sum of the three sugars; Tar = tartaric acid; Mal = malic acid; Cit = citric acid; SumA = sum of the three acids; Fir = firmness; Coh = cohesiveness; Spr = springiness; Che = chewiness.
Citation: HortScience 58, 1; 10.21273/HORTSCI16952-22
PCA of fruit quality compositions of Baoguang and Cuiguang subjected to different berry-thinning intensities under linkage greenhouse conditions. Loadings plot (A) and scores plot (B). BG = Baoguang; CG = Cuiguang; C = control; L = light berry thinning; M = moderate berry thinning; H = heavy berry thinning; ClM = cluster mass; ClL = cluster length; ClW = cluster width; BeW = berry weight; VeD = vertical diameter; HoD = horizontal diameter; WaC = water content; ToA = total anthocyanins; TSS = total soluble solids; TA = titratable acidity; Fru = fructose; Glu = glucose; Suc = sucrose; SumS = sum of the three sugars; Tar = tartaric acid; Mal = malic acid; Cit = citric acid; SumA = sum of the three acids; Fir = firmness; Coh = cohesiveness; Spr = springiness; Che = chewiness.
Citation: HortScience 58, 1; 10.21273/HORTSCI16952-22
PC1 accounted for 49.76% of the total variation and separated the berry-thinning treatments. Variables, including TSS/TA, firmness, TSS, and Fe, contributed positively to PC1 and maintained a relatively higher level in the berry-thinning treatments, whereas tartaric acid, cluster width, water content, and cluster mass contributed negatively to PC1 and were higher in the control. PC2 explained 35.55% of the total variation and showed a separation mainly according to the cultivar. Variables negatively correlative to PC2 were Ca, horizontal diameter, berry weight, Mg, sucrose, etc., which were higher in BG, whereas citric acid, cluster length, and malic acid contributing positively to PC2 gained a comparatively higher level in CG. In addition, with the heavier berry thinning, the treatments got closer to axis 1, which suggested that heavier berry thinning produced greater variation compared with control.
Discussion
Berry thinning by removing the number of berries in each bunch is a common viticulture technique to achieve better fruit quality (Roberto et al. 2017; Somkuwar et al. 2008). Lower cluster mass was obtained by heavier berry thinning (Table 1). Similar results were found in Monastrell and Shine Muscat grapes (Choi et al. 2021; Piernas et al. 2022). However, the effects of berry-thinning treatments on berry weight were controversial. Karoglan et al. (2014) reported that berry weights of Merlot and Cabernet Sauvignon were markedly increased by the berry-thinning treatment, which was consistent with the result found in Crimson Seedless grape berries (El-Razek et al. 2010). Nevertheless, the berry weight of Shine Muscat was unaffected by the berry-thinning treatment (Choi et al. 2021). In our study, M and H significantly increased berry weight and cultivars also showed significant effects on this parameter (Table 1). The genetic characteristics of the cultivar might play a key role in the effect of berry thinning on the berry weight.
Berry coloration was a major factor determining the fruit quality of table grapes and the accumulation of anthocyanin was responsible for the skin coloration. The ACs were higher with the heavier berry-thinning treatments (Table 2) and this was verified by Han et al. (2019) on the berries of Cabernet Sauvignon. The anthocyanin accumulation was highly regulated by the sunlight (Chorti et al. 2010; Guan et al. 2014; Matus et al. 2009). Shinomiya et al. (2015) reported that Kyoho berries exposed to high sunshine hours during the ripening season had good skin coloration, whereas berries exposed to low sunshine hours gained poor skin coloration. Consequently, we inferred that berry-thinning treatments made the inner berries receive more sunlight, which would be beneficial to regulating the synthesis of anthocyanin in the berries (Carbonell-Bejerano et al. 2014). Besides, the interaction of factors (cultivars × berry-thinning treatments) on total anthocyanins was noticeable (Table 2). That was probably because H had a greater increase in anthocyanin content of CG than that of BG (Supplemental Table 1). H increased ACs by 23.68% and 43.40% in BG and CG, respectively (Supplemental Table 1). One of the reasons could be the higher utilization efficiency of sunlight of CG in H, which could promote the synthesis of anthocyanin.
TSS, TA, and TSS/TA ratio had a great influence on fruit flavor. Ozer et al. (2012) reported that 50% berry thinning significantly improved the TSS of Reçel Üzümü berries. However, Gil et al. (2013) described that the TSS of Syrah was unaffected by berry thinning. In our study, H significantly increased TSS and cultivars exerted a larger effect on TSS than berry-thinning treatments (Table 3). These results indicated that TSS responses to berry thinning were more dependent on cultivars. Berry-thinning treatments decreased TA (Table 3), and a similar result was reported for Shine Muscat berries subjected to different densities (Choi et al. 2021). The TSS/TA ratio is more representative than the isolated index of sugars or acids and consumers preferred a high value of this index (Xu et al. 2017). In our study, berry-thinning treatments notably increased TSS/TA ratio (Table 3), which suggested that sweeter berries were produced by the berry thinning and those berries would be more popular in the market.
The compositions of sugars and organic acids also played an important role in defining the flavor of grape berries (Dai et al. 2011; Wen et al. 2013). Generally, the predominant sugars accumulated in grape berries were fructose and glucose (Kliewer 1965; Pavloušek and Kumšta 2011; Trad et al. 2017), which was consistent with the results of our study. Heavier berry thinning tended to obtain higher sugar components (Table 3), and a similar result was verified in ‘Cabernet Sauvignon’ grapes (Han et al. 2019). Although organic acid contents were low compared with sugars, organic acids influenced the taste and acceptability of grape berries (Shui and Leong 2002). Tartaric acid and malic acid were the main organic acids in grape berries and accounted for 90% of the total acids (Lamikanra et al. 1995; Liu et al. 2006; Wen et al. 2013), and similar results were found in our study. Keskin et al. (2013) found that acid components were affected by cultivars and berry thinning, which was consistent with the results of our study. Besides, the interaction of factors (cultivars × berry-thinning treatments) affected acid components (Table 3), which could be attributed to the different responses of the two cultivars to acid components in L (Supplemental Table 2). The effect of L on acid components was not consistent between the two cultivars (Supplemental Table 2), which indicated the effects of L on these indexes were more complex in cultivars.
Berry texture was an essential quality parameter that affected consumers (Iwatani et al. 2011; Sato and Yamada 2003). Little information was available on the influence of different berry densities on the berry texture. Berries with higher berry firmness commonly tended to have longer storage capacity (Deng et al. 2005). In our study, although texture indexes had inconsistent responses to the berry thinning, higher berry firmness was obtained by heavier berry thinning (Table 4), which indicated that berry thinning was beneficial to improve the storage capacity of grape berries.
Grape berries are rich in a variety of mineral nutrients, which has a vital role in human health (Tagliavini et al. 1998). People expected to produce berries with higher contents of mineral elements. Viticultural factors, such as fertilization and grafting (Jin et al. 2016; Tangolar et al. 2019), affected the contents of mineral elements. However, the effect of berry thinning on the nutrient elements was rarely reported. In our study, the contents of most mineral elements were increased by berry thinning. Besides, the interaction of cultivars by berry-thinning treatments has a significant effect on Ca (Table 5), and the reason could be that BG and CG had different responses to Ca content in L and M (Supplemental Table 2). Ca content of CG was markedly increased in L and M, whereas that of BG was unaffected by these treatments (Supplemental Table 3), which indicated the Ca content of CG was more sensitive to these two treatments than that of BG.
Conclusion
Berry thinning affected most of the quality variables. Heavier berry thinning tended to gain better fruit quality. Berry weight, TSS, fructose, glucose, ratio of TSS to TA, ACs, berry firmness, and the mineral contents (Ca, Fe, Na, Mg) were increased by berry thinning, whereas TA and organic acid profiles were decreased by berry thinning. Besides, cultivars and the interaction of factors (cultivars × berry-thinning treatments) exerted significant effects on most of the quality attributes. Future studies will focus on the interaction and more cultivars will be used to study this interaction.
References Cited
Aru, V., Nittnaus, A.P., Sorensen, K.M., Engelsen, S.B. & Toldam-Andersen, T.B. 2022 Effects of water stress, defoliation and crop thinning on Vitis vinifera L. cv. solaris: Part I: Plant responses, fruit development and fruit quality Metabolites 12 4 363 https://doi.org/10.3390/metabo12040363
Carbonell-Bejerano, P., Diago, M.P., Martínez-Abaigar, J., Martínez-Zapater, J.M., Tardáguila, J. & Núñez-Olivera, E. 2014 Solar ultraviolet radiation is necessary to enhance grapevine fruit ripening transcriptional and phenolic responses BMC Plant Biol. 14 183 1 16 https://doi.org/10.1186/1471-2229-14-183
Carmona-Jimenez, Y., Palma, M., Guillen-Sanchez, D.A. & Garcia-Moreno, M.V. 2021 Study of the cluster thinning grape as a source of phenolic compounds and evaluation of its antioxidant potential Biomolecules 11 2 227 https://doi.org/10.3390/biom11020227
Cheng, G.W. & Breen, P.J. 1991 Activity of phenylalanine ammonia-lyase (PAL) and concentrations of anthocyanins and phenolics in developing strawberry fruit J. Am. Soc. Hortic. Sci. 116 5 865 869 https://doi.org/10.21273/JASHS.116.5.865
Choi, K.O., Im, D., Park, S.J., Lee, D.H., Kim, S.J. & Hur, Y.Y. 2021 Effects of berry thinning on the physicochemical, aromatic, and sensory properties of Shine Muscat grapes Horticulturae 7 11 487 https://doi.org/10.3390/horticulturae7110487
Chorti, E., Guidoni, S., Ferrandino, A. & Novello, V. 2010 Effect of different cluster sunlight exposure levels on ripening and anthocyanin accumulation in Nebbiolo grapes Am. J. Enol. Vitic. 61 1 23 30
Coombe, B.G. 1995 Adoption of a system for identifying grapevine growth stages Aust. J. Grape Wine Res. 1 104 110 https://doi.org/10.1111/j.1755-0238.1995.tb00086.x
Dai, Z.W., Ollat, N., Gomès, E., Decroocq, S., Tandonnet, J.P., Bordenave, L., Pieri, P., Hilbert, G., Kappel, C., Van Leeuwen, C., Vivin, P. & Delrot, S. 2011 Ecophysiological, genetic, and molecular causes of variation in grape berry weight and composition: A review Am. J. Enol. Vitic. 62 4 413 425 https://doi.org/10.5344/ajev.2011.10116
Deng, Y., Wu, Y. & Li, Y. 2005 Changes in firmness, cell wall composition and cell wall hydrolases of grapes stored in high oxygen atmospheres Food Res. Int. 38 7 769 776 https://doi.org/10.1016/j.foodres.2005.03.003
El-Razek, A., Treutter, D., Saleh, M.M.S., El-Shammaa, M., Fouad, A.A., Abdel-Hamid, N. & Abou-Rawash, M. 2010 Effect of defoliation and fruit thinning on fruit quality of ‘Crimson Seedless’ grape Res. J. Agr. Biol. Sci. 6 289 295
Gil, M., Esteruelas, M., Gonzalez, E., Kontoudakis, N., Jimenez, J., Fort, F., Canals, J.M., Hermosin-Gutierrez, I. & Zamora, F. 2013 Effect of two different treatments for reducing grape yield in Vitis vinifera cv Syrah on wine composition and quality: Berry thinning versus cluster thinning J. Agr. Food Chem. 61 20 4968 4978 https://doi.org/10.1021/jf400722z
Guan, L., Li, J.H., Fan, P.G., Li, S.H., Fang, J.B., Dai, Z.W., Delrot, S., Wang, L.J. & Wu, B.H. 2014 Regulation of anthocyanin biosynthesis in tissues of a teinturier grape cultivar under sunlight exclusion Am. J. Enol. Vitic. 65 3 363 374 https://doi.org/10.5344/ajev.2014.14029
Han, W., Han, N., He, X. & Zhao, X. 2019 Berry thinning to reduce bunch compactness improves fruit quality of Cabernet Sauvignon (Vitis vinifera L.) Sci. Hortic. 246 589 596 https://doi.org/10.1016/j.scienta.2018.11.037
Intrigliolo, D.S., Llacer, E., Revert, J., Esteve, M.D., Climent, M.D., Palau, D. & Gómez, I. 2014 Early defoliation reduces cluster compactness and improves grape composition in Mandó, an autochthonous cultivar of Vitis vinifera from southeastern Spain Sci. Hortic. 167 71 75 https://doi.org/10.1016/j.scienta.2013.12.036
Iwatani, S.I., Yakushiji, H., Mitani, N. & Sakurai, N. 2011 Evaluation of grape flesh texture by an acoustic vibration method Postharvest Biol. Technol. 62 3 305 309 https://doi.org/10.1016/j.postharvbio.2011.06.009
Jin, Z.X., Sun, T.Y., Sun, H., Yue, Q.Y. & Yao, Y.X. 2016 Modifications of ‘Summer Black’ grape berry quality as affected by the different rootstocks Sci. Hortic. 210 130 137 https://doi.org/10.1016/j.scienta.2016.07.023
Karoglan, M., Osrečak, M., Maslov, L. & Kozina, B. 2014 Effect of cluster and berry thinning on merlot and cabernet sauvignon wines composition Czech J. Food Sci. 32 5 470 476
Keskin, N., İşçi, B. & Gökbayrak, Z. 2013 Effects of cane-girdling and cluster and berry thinning on berry organic acids of four Vitis vinifera L. table grape cultivars Acta Sci. Pol. 12 6 115 125
Kliewer, W.M. 1965 Changes in concentration of glucose, fructose, and total soluble solids in flowers and berries of Vitis vinifera Am. J. Enol. Vitic. 16 2 101 110
Lamikanra, O., Inyang, ID & Leong, S. 1995 Distribution and effect of grape maturity on organic acid content of red muscadine grapes J. Agr. Food Chem. 43 12 3026 3028 https://doi.org/10.1021/jf00060a007
Lee, J., Durst, R.W. & Wrolstad, R.E. 2005 Determination of total monomeric anthocyanin pigment content of fruit juices, beverages, natural colorants, and wines by the pH differential method: Collaborative study J. AOAC Int. 88 1269 1278
Liu, H.F., Wu, B.H., Fan, P.G., Li, S.H. & Li, L.S. 2006 Sugar and acid concentrations in 98 grape cultivars analyzed by principal component analysis J. Sci. Food Agr. 86 10 1526 1536 https://doi.org/10.1002/jsfa.2541
Matus, J.T., Loyola, R., Vega, A., Peña-Neira, A., Bordeu, E., Arce-Johnson, P. & Alcalde, J.A. 2009 Post-veraison sunlight exposure induces MYB-mediated transcriptional regulation of anthocyanin and flavonol synthesis in berry skins of Vitis vinifera J. Expt. Bot. 60 3 853 867 https://doi.org/10.1093/jxb/ern336
Ozer, C., Yasasin, A.S., Ergonul, O. & Aydin, S. 2012 The effects of berry thinning and gibberellin on Recel Uzumu table grapes Pak. J. Agric. Sci. 49 2 105 112
Pavloušek, P. & Kumšta, M. 2011 Profiling of primary metabolites in grapes of interspecific grapevine varieties: Sugars and organic acids Czech J. Food Sci. 29 4 361 372
Piernas, J., Giménez, M.J., Noguera-Artiaga, L., García-Pastor, M.E., García-Martínez, S. & Zapata, P.J. 2022 Influence of bunch compactness and berry thinning methods on wine grape quality and sensory attributes of wine in Vitis vinifera L. cv. ‘Monastrell’ Agronomy (Basel) 12 3 680 https://doi.org/10.3390/agronomy12030680
Roberto, S.R., Mashima, C.H., Colombo, R.C., Assis, A.M.D., Koyama, R., Yamamoto, L.Y., Shahab, M. & de Souza, R.T. 2017 Berry-cluster thinning to reduce compactness of ‘Black Star’ table grapes Cienc. Rural 47 4 e20160661 https://doi.org/10.1590/0103-8478cr20160661
Rolle, L., Siret, R., Segade, S.R., Maury, C., Gerbi, V. & Jourjon, F. 2011 Instrumental texture analysis parameters as markers of table-grape and winegrape quality: A review Am. J. Enol. Vitic. 63 1 11 28 https://doi.org/10.5344/ajev.2011.11059
Sato, A. & Yamada, M. 2003 Berry texture of table, wine, and dual-purpose grape cultivars quantified HortScience 38 4 578 581 https://doi.org/10.21273/HORTSCI.38.4.578
Shinomiya, R., Fujishima, H., Muramoto, K. & Shiraishi, M. 2015 Impact of temperature and sunlight on the skin coloration of the ‘Kyoho’ table grape Sci. Hortic. 193 77 83 https://doi.org/10.1016/j.scienta.2015.06.042
Shui, G. & Leong, L.P. 2002 Separation and determination of organic acids and phenolic compounds in fruit juices and drinks by high-performance liquid chromatography J. Chromatography 977 1 89 96
Somkuwar, R.G., Ramteke, S.D. & Satisha, J. 2008 Effect of cluster clipping and berry thinning on yield and quality of Thompson Seedless grapes Acta Hortic. 785 229 232 https://doi.org/10.17660/ActaHortic.2008.785.29
Song, C.Z., Wang, C., Xie, S. & Zhang, Z.W. 2018 Effects of leaf removal and cluster thinning on berry quality of Vitis vinifera cultivars in the region of Weibei Dryland in China J. Integr. Agr. 17 7 1620 1630 https://doi.org/10.1016/s2095-3119(18)61990-2
Szczesniak, A.S. 2002 Texture is a sensory property Food Qual. Prefer. 13 4 215 225 https://doi.org/10.1016/S0950-3293(01)00039-8
Tagliavini, M., Zavalloni, C., Rombolà, A.D., Quartieri, M., Malaguti, D., Mazzanti, F., Millard, P. & Marangoni, B. 1998 Mineral nutrient partitioning to fruits of deciduous trees Acta Hortic. 512 131 140
Tangolar, S., Alkan Torun, A., Ada, M., Aydin, O. & Kaçmaz, S. 2019 The effect of microbial fertilizer applications on grape yield, quality and mineral nutrition of some early table grape varieties Selcuk J Agr Food Sci. 33 2 62 66 https://doi.org/10.15316/sjafs.2019.157
Trad, M., Boge, M., Ben Hamda, H., Renard, C.M. & Harbi, M. 2017 The glucose–fructose ratio of wild Tunisian grapes Cogent Food Agr. 3 1 1374156 https://doi.org/10.1080/23311932.2017.1374156
Wang, Z., Zhou, J., Xu, X., Perl, A., Chen, S. & Ma, H. 2017 Adoption of table grape cultivars: An attribute preference study on Chinese grape growers Sci. Hortic. 216 66 75 https://doi.org/10.1016/j.scienta.2017.01.001
Wen, Y.Q., Cui, J., Zhang, Y., Duan, C.Q. & Pan, Q.H. 2013 Comparison of organic acid levels and L-IdnDH expression in Chinese-type and European-type grapes Euphytica 196 1 63 76 https://doi.org/10.1007/s10681-013-1014-z
Xi, X., Zha, Q., He, Y., Tian, Y. & Jiang, A. 2020 Influence of cluster thinning and girdling on aroma composition in ‘Jumeigui’ table grape Sci. Rep. 10 1 6877 https://doi.org/10.1038/s41598-020-63826-7
Xu, C., Yagiz, Y., Zhao, L., Simonne, A., Lu, J. & Marshall, M.R. 2017 Fruit quality, nutraceutical and antimicrobial properties of 58 muscadine grape varieties (Vitis rotundifolia Michx.) grown in United States Food Chem. 215 149 156 https://doi.org/10.1016/j.foodchem.2016.07.163
Impacts of different berry densities on cluster characteristics and physical and chemical indexes recorded in Baoguang and Cuiguang under linkage greenhouse conditions.
Impacts of different berry densities on sugar and acid components recorded in Baoguang and Cuiguang under linkage greenhouse conditions.
Impacts of different berry densities on mineral concentration recorded in Baoguang and Cuiguang under linkage greenhouse conditions.
