Table grape is a fruit with increasing interest due to its attributes and nutritional compounds. During recent years, new cultivars such as those without seeds and with new flavors have reached countries around the world. For this reason, postharvest treatments that retain fruit quality need to be improved. However, little is known to date about the biochemical and molecular mechanisms related with observed quality improvements. This review aims to examine existing literature on the different mechanisms. Special attention will be placed on molecular mechanisms which activate and regulate the different postharvest treatments applied in order to improve table grape quality.

It has been recognized that high CO₂ concentrations maintain the freshness of strawberries, reducing weight loss and the incidence of decay. Since strawberries have high tolerance threshold to CO₂, it is of interest to know what changes occur in cellular water distribution when the threshold is reached or exceeded. Moreover, as strawberries are prone to producing exudate during storage at low temperatures, application of technologies improving water retention is needed. Changes in bound water content were analyzed in relation to simple sugars, polyols, and fructooligosaccharides (FOS) in Fragaria vesca stored at low temperature (0 °C) in the presence of 0, 20, or 40 % CO₂. Fruits were analyzed at the end of a 3-day treatment and after transfer to air for one additional day. Unfavorable storage conditions were associated with a decrease in the levels of bound water and in that of 1-kestose and myo-inositol. However, the 1-kestose and myo-inositol content was enhanced when 40 % CO₂-treated strawberries were transferred to air at the same time as an increase in bound water content and a restoration of intracellular water took place. The ability of the fruit to modulate the accumulation of these compounds, and by extension their water binding strength, in conjunction with the pool of the bound water fraction, appears to be a mechanism associated with the maintenance of cellular structural integrity. Variation in the percentage of air space and in the weight loss rate produced by enhancing the CO₂ treatment during storage at 0 °C was also analyzed.

One of the greatest threats to wild strawberries (Fragaria vesca Mara des Bois) after harvest is the highly perishability at ambient temperature. Breeders have successfully met the quality demands of consumers, but the prevention of waste after harvest in fleshy fruits is still pending. Most of the waste is due to the accelerated progress of senescence-like process after harvest linked to a rapid loss of water and firmness at ambient temperature. The storage life of strawberries increases at low temperature, but their quality is limited by the loss of cell structure. The application of high CO₂ concentrations increased firmness during cold storage. However, the key genes related to resistance to softening and cell wall disassembly following transference from cold storage at 20°C remain unclear. Therefore, we performed RNA-seq analysis, constructing a weighted gene co-expression network analysis (WGCNA) to identify which molecular determinants play a role in cell wall integrity, using strawberries with contrasting storage conditions, CO₂-cold stored (CCS), air-cold stored (ACS), non-cold stored (NCS) kept at ambient temperature, and intact fruit at harvest (AH). The hub genes associated with the cell wall structural architecture of firmer CO₂-treated strawberries revealed xyloglucans stabilization attributed mainly to a down-regulation of Csl E1, XTH 15, Exp-like B1 and the maintenance of expression levels of nucleotide sugars transferases such as GMP and FUT as well as improved lamella integrity linked to a down-regulation of RG-lyase, PL-like and PME. The preservation of cell wall elasticity together with the up-regulation of LEA, EXPA4, and MATE, required to maintain cell turgor, is the mechanisms controlled by high CO₂. In stressed air-cold stored strawberries, in addition to an acute softening, there is a preferential transcript accumulation of genes involved in lignin and raffinose pathways. Non-cold stored strawberries kept at 20°C after harvest are characterized by an enrichment in genes mainly involved in oxidative stress and up-expression of genes involved in jasmonate biosynthesis. The present results on transcriptomic analysis of CO₂-treated strawberries with enhanced resistance to softening and oxidative stress at consumption will help to improve breeding strategies of both wild and cultivated strawberries.