Influence of pre-harvest factors on quality of a winter cycle, high commercial value, tomato cultivar

- Salinity increases fruit quality, however reducing marketable fruit yield.
- CO2 enrichment increases fruit yield without compromising organoleptic quality.
- High thermal levels and high CO2 concentration shorten the period of fruit development.
- The effective degree days model is useful to predict the period of fruit development.

The present study was conducted to study the effect of pre-harvest factors such as salinity and greenhouse air CO2 enrichment on the quality of a high commercial value, tomato cultivar. The experiment was carried out in two identical, adjacent multispan greenhouses, with polyethylene plastic covering. Hybrid Raf (cv. Delizia), tomato plants, were exposed to two treatments of salinity (5 and 7 dS m−1) and two ambient CO2 concentrations (350 and 800 μmol mol−1) in which CO2 enrichment was applied during the daytime according to a strategy linked to ventilation. The high salinity treatment (7 dS m−1) increased firmness (N), total soluble solids content (SSC), titratable acidity (TA) and the percentage of dry matter of the fruit (% DM), however, the pH was reduced. In return, CO2 enrichment did not affect firmness, TA and pH, whereas SSC and % DM were increased. On the other hand, the climatic variations as temperature, radiation and CO2 concentration, during the period of fruit development (PFD) affected its duration. The effective degree days (EDDs) model that combines temperature and radiation was used to study the relationship with the PFD and quality parameters. A good correlation was found between PFD and EDDs (r2 = 0.95). Thus the thermal time model by incorporating radiation can be recommended for our region to predict the period of fruit development in a hybrid Raf tomato crop. With respect to quality parameters, an increasing trend was observed between fruit firmness in high salinity conditions and the EDDs though the correlation was weak (r2 = 0.50). We did not find a relationship on SSC, TA, pH and % DM. CO2 enrichment shortened two days of the PFD and salinity did not affect this parameter. According to the results, CO2 enrichment allows increasing the production of a high value commercial crop grown under saline conditions by reducing the time needed for complete fruit development without compromising organoleptic quality.