Effects of Abscisic Acid/Ethephon Treatments on Berry Development and Maturation in the Yellow-green Skinned ‘Shine Muscat’ Grape

Abstract

Abscisic acid (ABA) and ethylene are well-known phytohormones that are involved in the maturation of grape berries and other fruits. However, the process of yellow-green skinned grape berry maturation is not well understood due to difficulties in determining grape maturity from changes in skin color. Skin browning during maturation is a major commercial problem in some yellow-green skinned grape cultivars including 'Shine Muscat'. To resolve this issue, a better understanding of the mechanisms involved in grape maturation and skin-browning is needed. We treated 'Shine Muscat' grape clusters at the veraison stage (45-50 DAFB) with spray applications of ABA or ethephon. These treatments produced darker colors and increased the transresveratrol and flavonol contents of berry skins. The ABA and ethephon treatments significantly increased the severity of skin browning. Changes in the expression of genes involved in polyphenol biosynthesis and oxidation were consistent with increases in polyphenols and the severity of browning in berry skins. The expression of VvACO2 and VvYUC1 genes, which are involved in ethylene and auxin biosynthesis, respectively, were upregulated in berries with brown skins. Although ABA treatment also increased the size of the berries, the effect of ethephon treatment on berry maturation was similar to, or greater than, that of ABA treatment. In berry skins, the expression of VvACO3, which is involved in phytohormone biosynthesis, increased significantly in response to ABA treatment. Overall, the changes in gene expression produced by ABA and ethephon treatments differed. Therefore, different mechanisms may regulate the physiological responses to ABA and ethephon, although both treatments accelerate berry maturation.

Effects of Gibberellic Acid/Cytokinin Treatments on Berry Development and Maturation in the Yellow-green Skinned ‘Shine Muscat’ Grape

“…In this study, CPPU treatment was more effective than GA 3 treatment at the veraison stage, although the application concentrations were different. Berry maturation was delayed by GA/CK treatment and this was the opposite result of ABA/ethephon treatment (Suehiro et al, 2019). Brassinosteroid and jasmonic acid have also been reported to promote grape berry maturation and ripening (Jia et al, 2016;Symons et al, 2006).…”

“…The degree of skin browning in each whole berry cluster was determined based on criteria developed by Mochida et al (2013). Individual berries were assigned to categories of browning as indicated in Suehiro et al (2019).…”

“…Primer sets were prepared for the following phytohormone-related genes: the 9-cis-epoxycarotenoid dioxygenase (NCED)1 and NCED2 genes, which encode enzymes that are involved in ABA biosynthesis (Speirs et al, 2013); type 2C protein phosphatases (PP2Cs) genes, which are negative regulators of ABA signaling (Boneh et al, 2012;Gambetta et al, 2010); 1-aminocyclopropane-1carboxylate oxidase (ACO) genes from the ethylene biosynthesis pathway (Muñoz-Robredo et al, 2013); VvEIN3, which encodes a transcription factor in the ethylene signaling pathway (Chervin and Deluc, 2010); GA 2-oxidase (GA2ox), GA3ox, and GA20ox from the GA biosynthesis pathway (Giacomelli et al, 2013); the gibberellic acid insensitive (GAI)1 gene, which encodes a transcription factor with a DELLA domain that is involved in GA signaling (Boss and Thomas, 2002); the gibberellic acid insensitive (GAI)1 gene, which encodes a transcription factor with a DELLA domain that is involved in GA signaling (Boss and Thomas, 2002); the gibberellin-insensitive dwarf 1 (GID1) gene, which encodes one of the GA receptors (Acheampong et al, 2015); the cytokinin histidine kinase receptors (CHKs) genes, which encode membrane-bound homodimeric proteins that are involved in cytokinin signaling (Böttcher et al, 2015); the VvYUC1 gene, which encodes a key enzyme that is involved in auxin biosynthesis (Böttcher et al, 2013); and the auxin response factor (ARF)1 gene, which encodes a transcription factor that is involved in auxin signaling (Wan et al, 2014). Primer sets for the VvPP2Cs, VvGA2ox, VvGA20ox, VvGA3ox, VvGAI1, VvGID1, and VvCHKs were newly designed by Suehiro et al (2019) based on DNA sequence information provided by previous studies (Acheampong et al, 2015;Boneh et al, 2012;Boss and Thomas, 2002;Böttcher et al, 2015;Giacomelli et al, 2013). The primer sequences for each of the target genes are listed in Supplementary Table 1.…”

Phytohormones in fruit development and maturation

“…This has been demonstrated in grapes, where berries exposed to exogenous applications of CK and GA at veraison grow larger fruits and accumulate lower amounts of hexose sugars during ripening. In treated berries, downregulation of ABA and ethylene biosynthesis was directly correlated with reduced color changes and prolonged greenness in the fruit pericarp, whereas ABA and ethylene signaling were unsuppressed in control fruits that exhibited unperturbed ripening (Suehiro et al ., 2019).…”

Oxalic Acid Preharvest Treatment Improves Colour and Quality of Seedless Table Grape ‘Magenta’ Upregulating on-Vine Abscisic Acid Metabolism, Relative VvNCED1 Gene Expression, and the Antioxidant System in Berries

“…The role of various transport systems in ABA translocation, stomatal, cuticular, and root responses, and also osmotic adjustment has been summarised by Jarzyniak and Jasiński (2014). In contrast, other reports have shown that VvNCED1 was upregulated by ABA and ethephon treatments (Pilati et al, 2017;Suehiro et al, 2019), explaining the intracellular ABA level measured by Pilati et al (2017).…”