Effects of foliar applications of zinc on fruit biofortification and quality traits of greenhouse mini plum tomato cultivars

In recent years, concerns have emerged about inadequate zinc (Zn) levels among European populations. Agronomic biofortification could represent an effective strategy to address this mineral deficiency, particularly when applied to widely consumed horticultural products, such as tomatoes. This study evaluated the effects of Zn biofortification on the greenhouse-grown mini plum tomatoes ‘Fanello’ (red fruit) and ‘Black Pearl’ (brownish fruit) through ten foliar applications of Zn-EDTA (1.7 mmol Zn L−1). Compared to control, Zn application did not affect yield but increased total Zn concentration (+66 %) while reducing Zn bioaccessibility (−26 %), leading to a lower increase in bioaccessible Zn (+23 %). ‘Black Pearl’ had lower Zn content than ‘Fanello’ (113 vs. 149 μg 100 g−1), but showed a higher increase in bioaccessible Zn in response to Zn-EDTA (+31 %). Treated fruits displayed only a 7 % increase in dry matter content, but ‘Black Pearl’ displayed stronger variations than ‘Fanello’ in terms of total sugars (−13 %), malic acid (−12 %), citric acid (+12 %), TSS/TA ratio (−11 %), lycopene (−8 %), and tomatine (−65 %). Overall, these findings highlight both the potential and limits of biofortification to enhance the Zn content in mini plum tomatoes, underlining significant genotype-dependent side effects that may worsen the fruits' organoleptic and functional traits.