The Influence of Diluted Seawater and Ripening Stage on the Content of Antioxidants in Fruits of Different Tomato Genotypes

Abstract

The aim of this study was to investigate if the combined effect of diluted seawater and ripening can improve the beneficial nutritional properties of tomato fruits from an antioxidant point of view. To reach the goal, different tomato cultivars and breeding lines, genetically modified for ripening, were investigated, and analysis of NADPH and NADP + as well as of the main antioxidants such as ascorbic acid, lipoic acid, and tocopherols was performed at two ripening stages. The research was conducted on berries of the following genotypes of tomato: cv. Jama, Gimar wild type, Gimar gf, and Gimar nor. The mutant gf is a typical "stay green" mutant, characterized by an incomplete loss of chlorophyll; the nor mutation is characterized by a reduced biosynthesis of ethylene and carotenoids. Both ripening and salinity induced an oxidative stress, and the sensitivity to salt treatment was genotype-dependent. The genotypes cv. Jama and Gimar gf line showed increases in ascorbic acid, lipoic acid, and R-tocopherol during both ripening and salt treatment whereas total ascorbate and tocopherols decreased in the berries from salt-treated plants of Gimar wild type. Ripening also determined decreases in ascorbate and tocopherol amounts in the Gimar nor line where a positive effect of ripening and salinity was observed.

Irrigation with Diluted Seawater Improves the Nutritional Value of Cherry Tomatoes

“…This finding is a confirmation of what was previously found for other tomato genotypes (6), even if the present research demonstrates how well cherry tomato tolerates the damaging effects of oxidative stress caused by high salinity, thus improving its nutritional quality. In fact, this capacity appears to be higher with respect to that of the other genotypes previously studied (6), where NADPH decreased following salinity.…”

“…This capacity seems higher with respect to other genotypes previously studied (6), in which NADPH decreased following salinity. The higher tolerance of cherry tomato is also demonstrated by its capacity to give marketable fruits when irrigated with seawater diluted to 12% instead of 10%, which was employed for irrigation of cv.…”

“…The nutritional value of tomato fruits is dependent on the presence of antioxidant compounds such as vitamin C (ascorbic acid) and vitamin E (tocopherols), the consumption of which is related to oxidative processes that could be induced by natural physiological processes such as ripening or by environmental changes such as salinity and drought (6). Indeed, a high salt level in the root zone may stimulate the production of oxidizing agents in plant cells and may result in redox reactions leading to metabolic alterations and reduced fruit yield ( Table 2).…”

“…Nothwithstanding the reduction of fruit weight, cherry tomato irrigated with diluted seawater appeared to be tastier, with a higher increase in titratable acidity and concentration of reducing sugars in comparison with control berry ( Table 2). Cherry tomatoes are generally characterized by higher dry matter and soluble solid levels ( Table 2) than normal-sized fresh market cultivars (6). High dry matter and soluble solids are desirable characteristics for the canned tomatoes industry because they improve the quality of the processed product (20).…”

Tomato fruit quality as influenced by salinity and nitric oxide

“…For example, chlorogenic acid increased while cinnamic acid decreased in salt stressed tomato fruit. These results were in accordance with the results in several other plants such as artichoke leaves and tomato fruits (Sgherri et al, 2007;Rezazadeh et al, 2012) grown under saline conditions. Furthermore, several types of wounding of apple fruits and leaves induce accumulation of chlorogenic acid and flavanols via activating PAL (Michalek et al, 1999).…”