Fruit cracking is a persistent challenge for table grape growing. To investigate the mechanism of this disorder, a comprehensive two-year investigation was conducted to assess the fruit cracking percentage of 15 table grape (Vitis vinifera L.) varieties. Based on the findings, the cracking-susceptible variety ‘Xiangfei’ and the cracking-resistant variety ‘Zuijinxiang’ were selected for further study. Fruit growth curves for ‘Zuijinxiang’ and ‘Xiangfei’ were plotted based on fruit diameter and total soluble solids content, revealing that both varieties exhibited typical double-sigmoidal patterns that were highly similar. The period between 48 and 53 days after full bloom (DAFB) was identified as the critical phase for fruit cracking incidence. Furthermore, during the fruit cracking period, ‘Xiangfei’ fruit exhibited significantly higher water content and mesocarp cell area compared with those of ‘Zuijinxiang’. Applying aquaporin inhibitors (nano-silver) to ‘Xiangfei’ berries reduced fruit water uptake and cracking percentage, whereas applying aquaporin activators (forskolin) to ‘Zuijinxiang’ berries increased fruit water uptake and cracking percentage. Additionally, expression analysis of six genes associated with plasma membrane intrinsic proteins (PIPs) synthesis (VvPIP1;1, VvPIP1;2, VvPIP1;3, VvPIP2;1, VvPIP2;2, and VvPIP2;3) revealed that only the expression level of VvPIP1;1 was higher in ‘Zuijinxiang’ than in ‘Xiangfei’ during the fruit cracking period, whereas the expression levels of the other genes exhibited no significant difference between the two varieties. Transgenic overexpression of VvPIP1;1 in tomato resulted in increased fruit water content, enlarged mesocarp cell size, and enhanced fruit cracking percentage. These findings indicate that VvPIP1;1 plays a pivotal role in controlling grape berry cracking.

Nectarine [Prunus persica (L.) Batsch var.] fruits are highly susceptible to cracking during the ripening process, which significantly decreases their commercial value. In this study, we investigated the underlying mechanism of nectarine fruit-cracking using two nectarine varieties, namely, "Qiannianhong" (cracking-susceptible) and "CR1012" (cracking-resistant). Our findings indicate that nectarine fruit-cracking occurs during the second stage of fruit expansion. Despite no differences in epicarp cell size between "Qiannianhong" and "CR1012", the mesocarp cells of "Qiannianhong" were larger than those of "CR1012". Moreover, a comparison of starch hydrolysis between the two varieties revealed that "CR1012" had higher starch content in the mesocarp but lower soluble sugar content compared to "Qiannianhong". Additionally, by testing the α-amylase and β-amylase activity of the mesocarp, our results showed a difference only in α-amylase activity between the two varieties. Furthermore, qRT-PCR detection indicated a higher expression level of the PpAmy1 (α-amylase synthesis gene) in "Qiannianhong" compared to "CR1012". To further investigate the role of PpAmy1, we employed RNAi technology to suppress its expression in "Qiannianhong" fruits. The results showed a significant reduction in α-amylase activity, starch hydrolysis, soluble sugar content, cell size of the mesocarp, and fruit-cracking. These findings underscore the pivotal role of PpAmy1 in the occurrence of nectarine fruit cracking.

The seedless treatment of seeded table grapes can have a negative impact on the table grape industry due to the occurrence of berry abscission during storage. This study aimed to investigate grape berry abscission by utilizing two distinct cultivars of table grapes, specifically ‘Ziqiu’ and ‘Shine Muscat’. The results revealed that seedless treatment grapes had a higher percentage of berry abscission during post-harvest storage than seeded ones. This may be attributed to the interaction between auxin and ethylene. In the early stage of storage, the higher level of auxin in the abscission zone of seeded grapes compared to seedless grapes may be associated with the continued high expression of auxin synthesis genes (VvYUC2 and VvYUC4) and transport gene (VvPIN4) in seeded grape seeds, as well as auxin transport gene (VvAUX1) in the abscission zone. The higher auxin content in the abscission zone enhances the expression of ethylene receptor genes (VvETR1, VvETR2, and VvEIN4), thereby reducing the sensitivity of the abscission zone to ethylene and decreasing the berry abscission percentage. Consequently, enzymes such as polygalacturonase (PG), pectinesterase (PE), and beta-galactosidase (β-GAL) are quickly activated, leading to pectin degradation and the initiation of the abscission process. Increased ethylene sensitivity in the abscission zone also leads to a reduction in superoxide dismutase (SOD) and catalase (CAT) activities, causing reactive oxygen species (ROS) to accumulate, and malondialdehyde (MDA) content to rise. Which results in cell membrane damage, and an acceleration of the grape berry abscission process. This study sheds light on the mechanisms behind grape berry abscission in response to seedless treatment and provides valuable insights for the table grape industry to improve the storage and transportation of seedless grapes.

Colletotrichum gloeosporioides is a major pathogenic fungus that causes anthracnose in stored mangoes, and it exhibits higher pathogenicity compared to Colletotrichum acutatum. This study primarily investigates the mechanism by which riboflavin prevents mango anthracnose caused by Colletotrichum gloeosporioides. In vitro experiments demonstrated that a concentration of 1.0 mmol L-1 riboflavin exhibited a strong inhibitory effect on spore germination of Colletotrichum gloeosporioides strains isolated from different major mango-producing regions in China, surpassing the efficacy of the chemical agent pyrimethanil. Furthermore, mango fruits infected with Colletotrichum gloeosporioides and treated with 1.0 mmol L-1 riboflavin exhibited a significant reduction in disease index. The mechanism behind this is that riboflavin not only generated reactive oxygen species (ROS) but also induced the production of ROS in the fruit during the early stages of storage, directly killing Colletotrichum gloeosporioides. Additionally, riboflavin activated phenylalanine ammonia lyase (PAL) and peroxidase (POD), leading to the production of total phenols and lignin, enhancing the fruit's disease resistance. Riboflavin also increased the activity of β-1,3-glucanase (GLU) and chitinase (CHI), which can disrupt the cell wall of Colletotrichum gloeosporioides. Moreover, riboflavin enhanced the activity of superoxide dismutase (SOD) and catalase (CAT) in the fruit, reducing weight loss percentage and minimizing the degradation of total soluble solids (TSS). These findings highlight the efficacy of riboflavin in preventing and controlling mango anthracnose.

To explore the fruit-cracking mechanism in nectarine, we compared three cracking-susceptible nectarine varieties (‘Huaguang’, ‘Yanguang’, and ‘Zaohongzhu’) and one cracking-resistant nectarine variety (‘Shuguang’). Our findings indicate that ‘Shuguang’ nectarines exhibited significantly higher levels of calcium, calcium pectinate, total pectin, cellulose, Na 2 CO 3 -soluble pectin and CDTA-soluble pectin in the peel compared to ‘Huaguang’, ‘Yanguang’, and ‘Zaohongzhu’. In contrast, the activities of polygalacturonases, pectinesterases, β-galactosidases, and cellulase were significantly lower in ‘Shuguang’. Interestingly, no significant differences were observed in indole-3-acetic acid and gibberellic acid content between ‘Shuguang’ and the other three cracking-susceptible nectarine varieties. However, the abscisic acid content in ‘Shuguang’ was significantly lower. Additionally, compared with the three cracking-susceptible nectarine varieties, the expression level of PpPIP1 (encoding the plasma membrane intrinsic protein, which can improve the permeability of plant cell membranes and greatly improve the efficiency of water diffusion across membranes) in flesh was significantly lower, and the expression levels of PpExp1 and PpExp2 (encoding expansins, which play significant roles in loosening and expanding cell wall components) were significantly higher in the peels of cracking-resistant nectarine varieties. These differences can provide a basis for further study of the mechanism of nectarine fruit-cracking.

Fruit cracking seriously affects the commercial value of table grapes. To explore whether cell wall disassembly influences grape berry cracking, first, the differences in the cell wall metabolism were compared between cracking-resistant "Shennongjinhuanghou" (SN) and cracking-susceptible "Xiangfei" (XF) varieties. Our results showed that cell wall disassembly events were extremely different between "SN" and "XF." The cracking-resistant "SN" had a higher pectinmethylesterase activity in the early stage and lower polygalacturonase, β-galactosidase, pectate lyase, and cellulase activities from veraison, cooperatively yielding higher ionically bound pectin, covalently bound pectin, hemicellulose, and lower water-soluble pectin, leading to a stronger skin break force and elasticity and conferring "SN" with higher cracking resistance. Furthermore, the function of the VvPL1 gene in fruit cracking was verified by heterologously transforming tomatoes. The transgenic experiment showed that overexpressed fruits had a higher activity of pectate lyase from the breaking stage and a lower level of covalently bound pectin, ionically bound pectin, cellulose, and hemicellulose and a higher level of water-soluble pectin at the red ripe stage, which resulted in a significantly reduced skin break force and flesh firmness and increased fruit cracking incidences. In conclusion, our results demonstrated that the cracking susceptibility of the grape berry is closely related to cell wall disassembly events and VvPL1 plays an important role in fruit cracking.

To explore the use of L-aspartic acid nano-calcium (nano-Ca) to reduce nectarine fruit-cracking, we sprayed the crack-susceptible nectarine cultivar 'Huaguang' [Prunus persica (L.) Batsch var. nectarina (Ait.) Maxim.] with nano-Ca. The results showed that nano-Ca could reduce the fruit-cracking percentage of nectarine by more than 20%. Nano-Ca was effective because it increased the calcium pectinate content of the peel, reduced the activity of cell-wall metabolic enzymes, and changed the peel structure and enhanced its toughness. We also found that nano-Ca enhanced calmodulin activity in leaves, upregulated key genes of sucrose synthesis in leaves and sucrose transport in stem phloem, and significantly increased the soluble sugar content in the fruit by more than 2%. In addition, Nano-Ca also enhanced calmodulin activity in peel and up-regulated key genes related to anthocyanin-synthesis, promoting anthocyanin accumulation in the peel. The result will lay a theoretical foundation for the physiological and molecular mechanisms of nectarine-cracking and its prevention.

Increasing the carotenoid content of nectarine (Prunus persica var. nucipersica) is of great significance for improving its quality and economic value. A two years study was carried out on 'Shuguang' nectarine to evaluate the effect of calcium chloride (Cl-Ca) and L-aspartic acid nano calcium [Ca (L-asp) - NPs] (nano-Ca) on carotenoid accumulation. The results show that both Cl-Ca and nano-Ca could increase the carotenoid content of nectarine fruit flesh, but the effect of nano-Ca was more significant. Nano-Ca is more easily absorbed by nectarine leaves and fruits, which improves the calmodulin activity of leaves, peel and flesh, and up-regulates the expression of carotenoid synthesis-related genes PpPSY, PpPDS, PpZDS, PpLCY-B, PpCHY-B and PpZEP. Nano-Ca also significantly up-regulated the expression of sucrose synthesis related genes PpSUS1 and PpSUS3 in leaves and sucrose transport related genes PpSUT2 and PpSUT4 in stem phloem, promoting the transport of more photosynthetic products to fruits, providing raw materials for carotenoid synthesis, and increasing the content of total sugars and ascorbic acid (Vc). In addition, nano-Ca can also up-regulate the expression levels of PpMYB10.1 and PpUFGT and promote total anthocyanins accumulation in peel. The results of our study will be useful for clarifying how nano-fertilizer improve the fruit quality of nectarine.

Table grapes are highly susceptible to abscission during storage and transportation, which significantly impacts their commercial value. To address this issue, ‘Thompson Seedless’ grapes were used as the test material, and two preharvest treatments, namely nano-calcium (nano-Ca) and CaCl 2 (Cl–Ca), were sprayed 2 weeks before harvest. The findings revealed that Cl–Ca had minimal effects on grape characteristics postharvest, while nano-Ca significantly increased the calcium content in fruits, rachis, and abscission zone (AZ) and inhibited ethylene production in these sections by suppressing the expression level of VvACO1 . Furthermore, nano-Ca increased pectin calcium content in the abscission zone, decreased the activities of polygalacturonase (PG) and pectinesterase (PE), delayed pectin degradation, reduced weight loss percentage, decay percentage, malondialdehyde (MDA) content, and relative conductivity, and maintained a higher berry detachment force (BDF) and lower berry abscission percentage. Overall, our research demonstrates that nano-Ca is a promising method to reduce berry abscission in table grapes during storage and transportation.

Berry abscission is a serious problem in table grape during postharvest storage and transport, causing significant economic losses. To explore the mechanism of berry abscission, we compared the abscission-susceptible grape genotype 'Hutai No. 8' with the abscission-resistant grape genotype 'Xiangfei' during post-harvest storage. Compared with 'Xiangfei', in 'Hutai No. 8', the berry detachment force was lower and the berry abscission percentage was higher; the contents of auxin and gibberellin in the berries, rachis and abscission zone were lower, and the contents of abscisic acid and ethylene were higher. Compared with 'Xiangfei', 'Hutai No. 8' had higher activities cell wall-degrading enzymes in the abscission zone; lower contents of total pectin and intact pectin fractions, and higher contents of degraded pectin. The activities of antioxidant enzymes in the abscission zone were lower in 'Hutai No. 8' than in 'Xiangfei', resulting in higher contents of reactive oxygen species and malondialdehyde, and higher relative conductivity. The distribution of calcium in different fractions differed between the two varieties. Ultimately, these differences resulted in softer berries and higher berry weight loss percentage and decay percentage in 'Hutai No. 8' than in 'Xiangfei' during storage. These results shed light on the mechanism of grape berry abscission during storage.

The problem of berry abscission often occurs during the postharvest storage and transport of table grapes; this seriously affects the commodity value and brings major losses to growers and sellers. The objective of this study was to investigate the effects of nordihydroguaiaretic acid (NDGA, which can reduce ABA synthesis by down-regulating the expression level of VvNCED1), on berry abscission during storage. After NDGA treatment, the decline of berry detachment force was delayed, and the percentage of berry abscission was reduced. The expression levels of VvNCED1 and VvACO1 in fruit and rachis were down-regulated, and the synthesis of abscisic acid (ABA) and ethylene in fruit and rachis were decreased by NDGA treatment. The activity of pectinesterase, polygalacturonase and cellulase, the malondialdehyde content and relative conductivity were lower than in the control. NDGA treatment also delayed the decline of total soluble solids, titratable acids, vitamin C and weight loss. Our results will help researchers to characterize the mechanism responsible for berry abscission during storage and transportation.

Fruit cracking is a phenomenon involving the splitting of the fruit peel, which causes considerable economic losses. The objective of the present study was to determine whether a nordihydroguaiaretic acid (NDGA) treatment can decrease the incidence of grape berry cracking in the cracking-susceptible Vitis vinifera cultivar 'Aishen Meigui'. The results indicated that NDGA can significantly decrease the fruit-cracking rate. There may be two reasons for this observation. Firstly, the NDGA treatment decreased the synthesis of endogenous abscisic acid (ABA) as well as the soluble sugar and total soluble solid contents, which ultimately lowered the osmotic pressure, water absorption capacity, and peel turgor pressure. Second, the decrease in the endogenous ABA content also decreased the pectin methylesterase and polygalacturonase activities, delayed the degradation of pectin, increased the peel protopectin content, enhanced the peel mechanical properties, and increased the resistance to fruit cracking.

Fruit cracking is a physiological disorder in many plant species that leads to severe economic losses. The aim of this study was to investigate the effect of calcium on fruit cracking and explore the underlying mechanisms. We studied the effect of exogenous calcium on grape berry cracking, calcium absorbance and distribution, and cell wall metabolism in the cracking-susceptible cultivar 'Xiangfei'. Calcium significantly reduced the frequency of fruit cracking, increased the break force of the berry skin, and stimulated storage of calcium. In addition, calcium increased the content of protopectin and inhibited the increase in content of water-soluble pectin, by regulating the transcription and activities of enzymes associated with cell wall metabolism. Taken together, the results indicated that dipping grape berries in calcium solution is effective in preventing fruit cracking by stimulating calcium uptake, inhibiting cell wall disassembly, and promoting cell wall strengthening.

BACKGROUND:Grape is an economically valuable fruit around the world. However, some cultivars are prone to fruit cracking during ripening, leading to severe losses.OBJECTIVE:We aimed to find important metabolisms related to fruit cracking during ripening process.METHODS:RNA-Sequence and analysis was applied to the pericarp of cracking-susceptible 'Xiang Fei' at 1 (W1), 2 (W2) and 3 weeks (W3) after veraison on Illumina HiSeq xten; RESULTS: Compared with W1, the berry cracking rate increased significantly in W2 and W3. Through transcriptomic analysis, a total of 22,609 genes were expressed in the grape pericarp, among which 805 and 2758 genes were significantly differentially regulated in W1-vs.-W2 and W1-vs.-W3 comparison, respectively. Besides, 304 and 354 genes were up- and down-regulated in both comparisons. The significantly enriched GO terms of both W1-W2 and W1-W3 are related to cell wall and wax biosynthesis. And lipid metabolism, which are involved in the top 20 enriched KEGG pathways of both comparisons, was related to wax biosynthesis. Further, GO enrichment analysis of differentially expressed genes (DEGs) with same regulatory changes also indicated that the continuously up-regulated DEGs are significantly enriched in cell wall component biosynthesis and hydrolase.CONCLUSION:These findings suggested that genes related to cell wall metabolism and cuticle biosynthesis may play important roles in regulating grape berry cracking. Our results provide a reference for further studies on the molecular mechanism underlying fruit cracking.

Spine grape (Vitis davidii Foex) is an important wild plant species in South China. To provide economical and environmentally safe ways to promote the precocious maturation of spine grape berries, the effects of riboflavin were investigated. Riboflavin affected the reactive oxygen species metabolism in spine grape berries by increasing superoxide radical production and the hydrogen peroxide content, and it impaired the activities of the antioxidant enzymes superoxide dismutase and catalase. Riboflavin also induced the upregulated expression of maturation-related genes in advance, and the earlier accumulation of anthocyanin and total soluble solids. Phenological observations revealed that the treated grape berries underwent a color-turning stage 9 days earlier than the control, and the maturation stage occurred 7 days earlier than the control. Thus, riboflavin may significantly promote the precocious maturation of spine grape berries.

Anthocyanin in grape skin has positive effects on fruit coloration, plant development and human health. Calcium is not only an essential macroelement for plant growth, but also a second messenger involved in regulating various physiological process. Calcium-containing sprays is an effective horticultural practice to improve anthocyanin accumulation during the ripening stages. However, the underlying mechanism of calcium-induced anthocyanin biosynthesis is largely unexplored, and few studies have analyzed the genome-wide gene expression in grape skin exposed to calcium treatment. In this study, Illumina RNA-Sequencing (RNA-Seq) was performed on grape skin at one week after whole-plant calcium-sprays. A total of 1894 significantly differentially expressed genes (DEGs) were affected by calcium treatment, including 1266 up-regulated and 628 down-regulated genes. Further, we found calcium triggered a large number of DEGs associated with calcium transport and signaling, anthocyanin biosynthesis and transport and regulation, sugar transport, and plant hormone biosynthesis and signaling. By analyzing the up/down-regulated DEGs, we clarified exogenous calcium may improve grape berry color in the following four pathways: (1) calcium increased total soluble sugars content, which may promote anthocyanin accumulation by activating transcription factors (TFs) related to anthocyanin biosynthesis; (2) calcium enhanced the accumulation of anthocyanin by stimulating the interaction between calmodulin and UDP-glucose : flavonoid 3-0-glucosyltransferase (UFGT); (3) Ca2+/calmodulin may modulate TFs related to anthocyanin, which will then stimulate the genes in the biosynthetic pathway; (4) calcium signal may stimulate the biosynthesis of JA (jasmonic acid) and ET (ethylene), which may enhance anthocyanin content by increasing endogenous sugar level or directly activating TFs related to anthocyanin biosynthesis. This work is the first comprehensive transcriptomic analysis of calcium-treated fruit and provides deep insight into the molecular mechanism of calcium-induced accumulation of anthocyanin.

The objective of this study was to clarify the effects of calcium treatments on the anthocyanin accumulation of 'Manicure Finger' grape berries. Calcium treatments increased the calcium contents and enhanced the calmodulin activities in grapevine leaves and berries, upregulated the expression of the sugar transporter genes SUC12 and SUC27 in leaves, promoted the transport of photosynthetic products to berries, and increased the expression of anthocyanin biosynthesis-related genes in the grape berry skin. These results indicate that the application of exogenous calcium enhances anthocyanin accumulation in 'Manicure Finger' grape berries in the following two ways: (1) calcium promotes the transport of photosynthetic products to berries, thereby providing the basic material required for anthocyanin biosynthesis; (2) calcium induces anthocyanin biosynthesis by regulating the expression of relevant structural and regulatory genes. Our results will help researchers characterize the mechanism responsible for the calcium-mediated promotion of anthocyanin biosynthesis in grapevine and related plant species.