Effects of Grafting and Fertilization Treatments on the Functional and Nutritional Quality of Eggplant Cultivars

The nutritional and functional quality of eggplants is heavily influenced by biological and technological factors. This study evaluated the effects of cultivar, rootstock, and fertilizers on the nutritional and functional quality of eggplant (Solanum melongena L.). Two commercial hybrids (Mirval and Black Pearl) were assessed with respect to two rootstocks (Solanum sylvatica and Rezistar F1) and three fertilization regimes: biological (Micoseed®), organic (Orgevit®), and chemical (Nutrispore®). These were compared with ungrafted and unfertilized cultivars. Fruit samples were analyzed for total polyphenol content (TPC), antioxidant capacity (ABTS and DPPH assays), chlorophyll a and b, lycopene, and tannin concentrations. Mirval exhibited significantly higher levels of TPC, antioxidant activity, photosynthetic pigments, and lycopene than Black Pearl. Ungrafted plants and those grafted onto S. sylvatica showed superior fruit quality, particularly when combined with organic or chemical fertilization. The highest concentrations of polyphenols (3.61 mg·100 g−1 DW), lycopene (3.18 mg·100 g−1 DW), and total chlorophylls were recorded for Mirval fruits from ungrafted or S. sylvatica-grafted plants under organic or chemical fertilization. These findings indicate that optimizing cultivar–rootstock combinations and fertilization management can significantly enhance the functional quality of eggplant fruits. The findings also support the use of organic fertilization as a sustainable strategy in protected vegetable production systems.