Effect of two exogenous plant growth regulators on the color and quality parameters of seedless table grape berries

Preharvest Application of Phenylalanine Induces Red Color in Mango and Apple Fruit’s Skin

Anthocyanins are secondary metabolites responsible for the red coloration of mango and apple. The red color of the peel is essential for the fruit’s marketability. Anthocyanins and flavonols are synthesized via the flavonoid pathway initiated from phenylalanine (Phe). Anthocyanins and flavonols have antioxidant, antifungal, and health-promoting properties. To determine if the external treatment of apple and mango trees with Phe can induce the red color of the fruit peel, the orchards were sprayed 1 to 4 weeks before the harvest of mango (cv. Kent, Shelly, and Tommy Atkins) and apple fruit (cv. Cripps pink, Gala and Starking Delicious). Preharvest Phe treatment increased the red coloring intensity and red surface area of both mango and apple fruit that was exposed to sunlight at the orchard. The best application of Phe was 2–4 weeks preharvest at a concentration of 0.12%, while a higher concentration did not have an additive effect. A combination of Phe and the positive control of prohydrojasmon (PDJ) or several applications of Phe did not have a significant added value on the increase in red color. Phe treatment increased total flavonoid, anthocyanin contents, and antioxidant activity in treated fruit compared to control fruits. High Performance Liquid Chromatography analysis of the peel of Phe treated ‘Cripps pink’ apples showed an increase in total flavonols and anthocyanins with no effect on the compound composition. HPLC analysis of ‘Kent’ mango fruit peel showed that Phe treatment had almost no effect on total flavonols content while significantly increasing the level of anthocyanins was observed. Thus preharvest application of Phe combined with sunlight exposure offers an eco–friendly, alternative treatment to improve one of the most essential quality traits—fruit color.

Application of Elicitors at Two Maturation Stages of Vitis vinifera L. cv Monastrell: Changes in Skin Cell Walls

The aim of this study was to evaluate whether the application of two pre-harvest elicitors—methyl-jasmonate (MeJ) and benzothiadiazole (BTH)—to Monastrell grapes, at two maturation stages, affected the composition and structure of the skin cell walls (SCWs) to differing extents. This study was conducted in 2016–2017 on Vitis vinifera L. cv Monastrell. A water suspension of MeJ and BTH, and a mixture of both, was applied at veraison and mid-ripening. The composition of the berry SCW was analyzed. Environmental conditions caused substantial changes in SCW composition, especially at high temperatures. Indeed, a reduction of approximately 50% in the biosynthesis of hemicellulose, proteins and total phenols was observed, accompanied by a slight increase in cellulose and lignin. However, the application of the treatments also caused changes in some SCW constituents: increases in the concentration of phenols, proteins and lignin were observed, especially when the MeJ and MeJ + BTH treatments were applied at veraison. Likewise, a reduction in uronic acids was observed in the MeJ + BTH treatment applied at veraison. These changes in the SCWs could affect their structural characteristics, and therefore influence grape handling in the field and in the winery. Further studies are needed to determine the extent to which MeJ and BTH treatments affect other skin characteristics.

Characterization and Action Mechanism Analysis of VvmiR156b/c/d-VvSPL9 Module Responding to Multiple-Hormone Signals in the Modulation of Grape Berry Color Formation

In recent years, more and more reports have shown that the miR156-SPL module can participate in the regulation of anthocyanin synthesis in plants. However, little is known about how this module responds to hormonal signals manipulating this process in grapes. In this study, exogenous GA, ABA, MeJA, and NAA were used to treat the 'Wink' grape berries before color conversion, anthocyanin and other related quality physiological indexes (such as sugar, aroma) were determined, and spatio-temporal expression patterns of related genes were analyzed. The results showed that the expression levels of VvmiR156b/c/d showed a gradually rising trend with the ripening and color formation of grape berries, and the highest expression levels were detected at day 28 after treatment, while the expression level of VvSPL9 exhibited an opposite trend as a whole, which further verifies that VvmiR156b/c/d can negatively regulate VvSPL9. Besides, VvmiR156b/c/d was positively correlated with anthocyanin content and related genes levels, while the expression pattern of VvSPL9 showed a negative correlation. Analysis of promoter cis-elements and GUS staining showed that VvmiR156b/c/d contained a large number of hormone response cis-elements (ABA, GA, SA, MeJA, and NAA) and were involved in hormone regulation. Exogenous ABA and MeJA treatments significantly upregulated the expression levels of VvmiR156b/c/d and anthocyanin structural genes in the early stage of color conversion and made grape berries quickly colored. Interestingly, GA treatment downregulated the expression levels of VvmiR156b/c/d and anthocyanin structural genes in the early color-change period, but significantly upregulated in the middle color-change and ripening stages, therefore GA mainly modulated grape berry coloring in the middle- and late-ripening stages. Furthermore, NAA treatment downregulated the expression levels of VvmiR156b/c/d and anthocyanin structural genes and delayed the peak expression of genes. Meanwhile, to further recognize the potential functions of VvmiR156b/c/d, the mature tomato transient trangenetic system was utilized in this work. Results showed that transient overexpression of VvmiR156b/c/d in tomato promoted fruit coloring and overexpression of VvSPL9 inhibited fruit coloration. Finally, a regulatory network of the VvmiR156b/c/d-VvSPL9 module responsive to hormones modulating anthocyanin synthesis was developed. In conclusion, VvmiR156b/c/d-mediated VvSPL9 participated in the formation of grape color in response to multi-hormone signals.

Effects of compound growth regulators on the anatomy of Jujube Leaf and Fruit

Effects of three compound growth regulators formulated with hypersensitivity protein, spermidine, salicylic acid and DA-6 (diethyl aminoethanol hexanoate) were tested on Xinjiang Jun Jujube. The doses of compound growth regulators were named as A (Hypersensitivity protein + spermidine + salicylic acid at the rate of 30 mg/L, 0.1 mmol/L and 0.25 mmol/L, respectively), B (Hypersensitive protein + spermidine + DA-6 at the rate of 30 mg/L, 0.1 mmol/L and 30 mg/L, respectively) and C (Spermidine + salicylic acid + DA-6 at the rate of 0.1 mmol/L, 0.25 mmol/L and 30 mg/L, respectively) versus a control group CK (contained only water). Fruit anatomical structures were compared after spraying. The results indicated that after spraying, the thickness of the upper and lower epidermal cells and the stratum corneum were increased. However, the upper epidermal stratum corneum became significantly thicker than the lower epidermis. Spraying with A improved the thickness of upper and lower epidermal cells, stratum corneum, the central vein and mesophyll. The cumulative effects of all these changes in leaf and fruit anatomical structures provided the resistance of the experimental fruit plant to stress. While the B and C regulators had inhibitory effects. So, the results obtained after spraying A category were beneficial to improve the stress resistance of the fruits. The length and cell area of pericarp and sarcocarp cells in the treatment groups were not changed significantly. But the length, number of sarcocarp cells and number of gaps were lower than those in the CK. This study can provide new measures for improving plant resistance in jujube production.

Effect of pre-harvest inactivated yeast treatment on the anthocyanin content and quality of table grapes

Due to the global warming, more and more often the red-pink grape varieties grown in the Mediterranean basin reveal an insufficient accumulation of anthocyanins and thus a scarce coloration. Nowadays, this is becoming an important technological issue, which may result in the reduction of the fresh market value of table grape. This study aimed at assessing the effect of the pre-harvest treatment by specific inactivated yeasts (YE) on the qualitative parameters and anthocyanin pattern of three red table grape varieties, which typically present poor and/or incomplete coloration during warm years. An increment of anthocyanins level up to almost seven folds corresponding to an improvement of red skin appearance was observed in all the treated table grapes, which was preserved after cold storage, too. While, no significant influence on chemical composition and berry texture and dimensions was found, meaning that YE did not cause appreciable taste changes in grapes.

How Pre-Harvest Inactivated Yeast Treatment May Influence the Norisoprenoid Aroma Potential in Wine Grapes

Carotenoids are important secondary metabolites in wine grapes and play a key role as potential precursors of aroma compounds (i.e., C13-norisoprenoids), which have a high sensorial impact in wines. There is scarce information about the influence of pre-harvest inactivated yeast treatment on the norisoprenoid aroma potential of grapes. Thus, this work aimed to study the effect of the foliar application of yeast extracts (YE) to Negro Amaro and Primitivo grapevines on the carotenoid content during grape ripening and the difference between the resulting véraison and maturity (ΔC). The results showed that β-carotene and (allE)-lutein were the most abundant carotenoids in all samples, ranging from 60% to 70% of total compounds. Their levels, as well as those of violaxanthin, (9′Z)-neoxanthin, and 5,6-epoxylutein, decreased during ripening. This was especially observed in treated grapes, with ΔC values from 2.6 to 4.2-fold higher than in untreated grapes. Besides this, a principal components analysis (PCA) demonstrated that lutein, β-carotene, and violaxanthin and (9′Z)-neoxanthin derivatives principally characterized Negro Amaro and Primitivo, respectively. Thereby, the YE treatment has proved to be effective in improving the C13-norisoprenoid aroma potentiality of Negro Amaro and Primitivo, which are fundamental cultivars in the context of Italian wine production.