Ethephon As a Potential Abscission Agent for Table Grapes: Effects on Pre-Harvest Abscission, Fruit Quality, and Residue.

Giuseppe Ferrara,Antonio Trani,Matthew W Fidelibus,Giuseppe Gambacorta,Angela M S Matarrese,Andrea Mazzeo,Carmela Pacucci

doi:10.3389/fpls.2016.00620

Abstract

Some plant growth regulators, including ethephon, can stimulate abscission of mature grape berries. The stimulation of grape berry abscission reduces fruit detachment force (FDF) and promotes the development of a dry stem scar, both of which could facilitate the production of high quality stemless fresh-cut table grapes. The objective of this research was to determine how two potential abscission treatments, 1445 and 2890 mg/L ethephon, affected FDF, pre-harvest abscission, fruit quality, and ethephon residue of Thompson Seedless and Crimson Seedless grapes. Both ethephon treatments strongly induced abscission of Thompson Seedless berries causing >90% pre-harvest abscission. Lower ethephon rates, a shorter post-harvest interval, or berry retention systems such as nets, would be needed to prevent excessive pre-harvest losses. The treatments also slightly affected Thompson Seedless berry skin color, with treated fruit being darker, less uniform in color, and with a more yellow hue than non-treated fruit. Ethephon residues on Thompson Seedless grapes treated with the lower concentration of ethephon were below legal limits at harvest. Ethephon treatments also promoted abscission of Crimson Seedless berries, but pre-harvest abscission was much lower (≅49%) in Crimson Seedless compared to Thompson Seedless. Treated fruits were slightly darker than non-treated fruits, but ethephon did not affect SSC, acidity, or firmness of Crimson Seedless, and ethephon residues were below legal limits.

Highlights

Table grapes that meet minimum maturity standards, including sugar and acid content, and the ratio of sugar to acid, are harvested by hand and typically marketed as entire or partial clusters
Ethephon-treated fruit was darker in color, and had lower C∗ and a greater h◦, indicating the fruit were somewhat more yellow colored than non-treated fruit and generally had a more mature appearance
A similar result was reported for Thompson Seedless treated with methyl jasmonate, another abscission agent (González-Herranz et al, 2009)

Summary

Introduction

Table grapes that meet minimum maturity standards, including sugar and acid content, and the ratio of sugar to acid, are harvested by hand and typically marketed as entire or partial clusters. The quality and value of the grapes are strongly affected by the size, texture, and color of the individual berries, and the overall appearance of the cluster (Fidelibus et al, 2010). These quality attributes are commonly achieved, in part, through the use various plant growth regulators (PGRs), agrochemicals with plant hormones or hormone-like compounds as active ingredients (Ferrara et al, 2013, 2015). Though the vast majority of table grapes are sold as entire or partial clusters, there is growing interest in marketing stemless fresh-cut grapes (Kou et al, 2007). Ethephon is the only compound registered for use on grapes, though the registrations are for improving the color of red and black fruited grapes, or hastening grape maturity, both at considerably lower use rates than what is required to stimulate berry abscission

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Conclusion