Selenium biofortification of greenhouse cherry tomato: impact on fruit quality traits and selenium content

The present experiment addressed the effects of selenium (Se) spray applications (as Na2SeO4, 3 mmol Se L-1) on soilless-grown cherry tomato (’Creativo’) at 2 different fruit ripening stages of clusters: immature green stage (T1) and breaker stage (T2). Tomatoes treated with tap water were used as controls. Compared to control, Se application at T2 increased fruit weight and firmness (by 12 and 14%, respectively), but decreased fruit dry matter content (-11%). The Se application had no significant effects on fruit mineral composition (in terms of K, Mg, Ca and Na), whereas control fruits had the highest values of total phenols (975 µmol GAE 100 g-1 FW) and hydrophilic antioxidant activity (289 µmol TE 100 g-1 FW). Moreover, the Se application at T2, reduced the fruit content of total carotenoids (-9%), ascorbic acid (-21%), and lipophilic antioxidant activity (-24%). Differently, the fruit Se content increased in response to both application times, reaching 47.2 (T1) and 80.2 µg 100 g-1 FW (T2). This corresponded to a coverage of 67.4 and 114.5% of the daily adequate Se intake, in T1 and T2, respectively, and resulting in hazard quotients equal to 0.16 (T1) and 0.27 (T2). Overall, these findings suggest that Se biofortification of cherry tomatoes can be effectively achieved through a single foliar application of Na2SeO4 at either the immature green or breaker stages, without exceeding the hazard threshold for adult nutrition. The breaker stage proved greater efficiency in accumulating Se in fruits. However, this was accompanied by reductions in the content of carotenoids, phenols, and ascorbic acid, as well as a decline in fruit antioxidant capacity.