Agronomic performance and fruit quality in greenhouse grown eggplant are interactively modulated by iodine dosage and grafting

Iodine (I) is considered an indispensable trace element for humans due to its capacity to promise a normal functions of thyroid hormones, preventing cretinism, goiter, reproductive failure, and diverse types of brain injury. Vegetable grafting is a technique for securing yield constancy and/or improving fruit quality. The study evaluated the combined effect of I-dosages and grafting onto Solanum torvum rootstock on ‘Birgah’ eggplant. Iodine at 100 or 300 mg L−1 enhanced marketable yield by 28.8% and 8.5%, respectively, compared with the control. Plants grafted onto S. torvum and self-grafted plants increased marketable yield by 53.0% and 45.8%, respectively compared with the ungrafted plants. I-biofortification determined a linear decrease in SSC as I-dosage increased. I-enrichment at 300 and 600 mg L−1 improved fruit dry matter and ascorbic acid compared with the control. The combinations of self-grafting × I-biofortification at 600 mg L−1 and ungrafting × I-biofortification at 600 mg L−1 improved total anthocyanins concentration by 8.5% and 9.1%, respectively, compared with the ungrafting × 0 I-biofortification combination. Exposing ungrafted plants to 600 mg I L−1 resulted in a significantly higher chlorogenic acid content compared to the control. Glycoalkaloids concentration in the fruits was always below the suggested safety value (200 mg 100 g−1 DW). Grafting enhanced proteins, K, Fe and Zn by 22.9%, 7.2%, 20.0% and 2.4%, respectively compared with ungrafting. I concentration in fruit of grafted plants varied from 0.67 mg kg−1 DW at 0 mg I L−1 to 188.67 mg kg−1 DW in plant biofortified with the highest I-dosage. The pulp browning potential was significantly dependent upon I-dosage and grafting with the lowest values found in fruits from grafted plants supplied with 0 or 100 mg I L−1. The present results suggested that I-biofortification at 300 or 600 mg L−1 and grafting, successfully boosted nutritional and functional traits of ‘Birgah’ eggplant, securing satisfactory yield and yield-related traits