Calcium chloride and 1-methylcyclopropene treatments delay postharvest and reduce decay of New Queen melon

Qiang Zhang,Xinwen Jin,Wenting Dai,Jixin Li

doi:10.1038/s41598-019-49820-8

Abstract

In this study, newly harvested New Queen melons were treated with calcium chloride (CaCl2) and 1-methylcyclopropene (1-MCP) alone or in combination before storage. The results showed that the respiration rate, ethylene release, the activity and gene expression of pectinases such as polygalacturonase (PG), pectin methylesterase (PME) and pectate lyase (PL) in New Queen melons were dramatically decreased by treatments with 0.18 mol/L CaCl2 and/or 1 μL/L 1-MCP. Meanwhile, the climacteric behavior and flesh hardness reduction were inhibited. We also found that softer melon flesh was more conducive to the growth and reproduction of decay-causing microorganisms according to their growth curves in melons that were different in flesh hardness, suggesting inhibiting fruit softening can slow down the growth of microorganisms in fruit flesh, and thus reduce fruit decay rate. The combined use of CaCl2 and 1-MCP was more effective in suppressing respiration rate, ethylene release and protopectin hydrolysis, which could greatly delay the softening, reduce the decay rate, and extend the shelf life of New Queen melons.

Highlights

Xinmi No 13 is an elite think-rinded cultivar of New Queen melon obtained after many generations of breeding and selection, and has become one of the popular Xinjiang melons, because of its good fruit appearance, high commercial value and unique flavor
It can binds to its receptor and accelerates fruit respiratory metabolism, and up-regulates the expression of pectinase encoding genes, promotes the production of pectinases, which hydrolyze protopectin, and change cell wall structures, and the fruits become soft as a result[11]
As an important component of plant cell wall structure, calcium inhibits the activity of cell-wall degrading enzymes

Summary

Introduction

Xinmi No 13 is an elite think-rinded cultivar of New Queen melon obtained after many generations of breeding and selection, and has become one of the popular Xinjiang melons, because of its good fruit appearance, high commercial value and unique flavor. New Queen melon is a climacteric variety, characterized by a dramatic rise in respiration rate and ethylene release after harvest, while the fruit matures and softens rapidly[1]. Delaying or inhibiting climacteric behavior and reducing the amount of ethylene released is an effective measure to delay the aging and softening of fruit. Li et al reported that calcium treatment reduced the respiration rate and ethylene release of netted melon[4]. The study of Chardonnet et al revealed that calcium treatment effectively inhibited the changes of cell wall components to maintain the fruit hardness of Golden Delicious apple[5]. The study of Deng et al showed that calcium treatment reduced the activity and gene expression of cell wall degrading enzymes, to maintain the hardness of grapefruit[6]. The effects of calcium and 1-MCP on physiological metabolism of melons have been rarely reported

Methods

Results

Conclusion