Pre- and Post-harvest Melatonin Application Boosted Phenolic Compounds Accumulation and Altered Respiratory Characters in Sweet Cherry Fruit

Abstract

The aim of the present study was to investigate the impact of exogenous melatonin (0. 5 mM) application through pre-harvest foliar spray and postharvest immersion, alone or in combination, on ripening parameters of sweet cherry (cv. Ferrovia) fruit and their relationship with bioactive compounds and gene expression at harvest as well after cold storage (0°C) for 12 days and subsequent room temperature (20°C) exposure for 8 h. Although several ripening traits were not influenced by melatonin, the combining pre- and post-harvest treatments delayed fruit softening at post-cold period. Preharvest spray with melatonin depressed fruit respiration at time of harvest while all applied treatments induced respiratory activity following cold, indicating that this anti-ripening action of melatonin is reversed by cold. Several genes related to the tricarboxylic acid cycle, such as PaFUM, PaOGDH, PaIDH, and PaPDHA1 were upregulated in fruit exposed to melatonin, particularly following combined pre- and post-harvest application. The accumulation of phenolic compounds, such as neochlorogenic acid, chlorogenic acid, epicatechin, procyanidin B1, procyanidin B2+B4, cyanidin-3-O-galactoside, and cyanidin-3-O-rutinoside along with the expression of several genes involved in phenols biosynthesis, such as PaSK, PaPAL, Pa4CL, PaC4H, and PaFNR were at higher levels in melatonin-treated cherries at harvest and after cold exposure, the highest effects being observed in fruits subjected to both pre- and post-harvest treatments. This study provides a comprehensive understanding of melatonin-responsive ripening framework at different melatonin application conditions and sweet cherry stages, thereby helps to understand the action of this molecule in fruit physiology.

Melatonin Treatment Improves Postharvest Preservation and Resistance of Guava Fruit (Psidium guajava L.)

“…Melatonin may enhance the respiration and improve the energy supply to maintain fruit quality [28]. Importantly, melatonin induced phenolic compound accumulation and related genes expression, which help to improve fruit quality and cold tolerance [54]. In the present work, it was established that melatonin repressed fruit respiration rates during the early storage period, but increased respiration during later storage, which corresponded to the enhanced total flavonoids and ascorbic acid accumulation.…”

“…Melatonin treatment effectively reduced the elevation of the respiratory rate in bananas [19], pears [25], mango fruits [27], as well as altered the secondary metabolism pathways, resulting in the delayed ripening process. Preharvest spray with melatonin depressed fruit respiration after harvest while melatonin induced respiratory activity following cold storage [54]. It indicated that the sweet cherry response to melatonin treatment involved a cold-dependent activation of the respiration and up-regulation of TCA cycle-related genes [54].…”

“…Preharvest spray with melatonin depressed fruit respiration after harvest while melatonin induced respiratory activity following cold storage [54]. It indicated that the sweet cherry response to melatonin treatment involved a cold-dependent activation of the respiration and up-regulation of TCA cycle-related genes [54]. It seems that cold storage may cause stress to sweet cherry fruit and give rise to ROS.…”

Effects of Melatonin Treatment on Sweet Cherry Tree Yield and Fruit Quality

“…In fact, ripening in sweet cherry, as well as in other fruit species, is a complex and coordinated process and each single parameter evolves at a particular pace [30]. In the 'Ferrovia' cultivar, foliar spray with 0.5 mM melatonin 2 and 1 weeks prior to harvest did not affect the ripening process, leading to fruit with similar TSS, TA and colour values than controls [21]. Accordingly, no significant effects of 0.1 or 0.01 mM melatonin treatment (applied 19 days before harvesting) on fruit firmness, TA or TSS were reported for the 'Prime Giant' cultivar by Tijero et al [20], although anthocyanin content was significantly decreased.…”

“…On the other hand, melatonin (0.01 and 0.1 mM) applied directly to fruit surface at stage II of development (green and large in size fruit) delayed fruit ripening, manifested by delayed anthocyanin accumulation, in the 'Prime Giant' cultivar [20]. On the contrary, foliar spray of sweet cherry 'Ferrovia' with 0.5 mM melatonin 2 and 1 weeks prior to harvest led to fruit with a higher content of the individual anthocyanins cyaniding 3-rutinoside, cyaniding 3-galactoside and cyaniding 3-glucoside at harvest, showing an acceleration of the fruit ripening process [21]. However, as far as we know, no literature is available regarding the effect of pre-harvest melatonin treatment on sweet cherry tree yield or fruit quality properties at harvest.…”