Exploring the Potential of Iodine in Mitigating Salinity Stress: Effects On Yield, Physio-biochemical Traits, and Fruit Quality of Sweet Pepper (Capsicum Annuum L.)

Iodine (KIO3) is not essential for plant growth but significantly contributes to the components involved in photosynthesis. The ameliorative roles of KIO3 on the yield and quality of plants under salinity stress are not perfectly understood. Therefore, this study investigated how three different concentrations of exogenously applied KIO3 (0, 50, and 100 µM) affected the yield, growth characteristics, photosynthetic pigments, and quality of sweet pepper plants exposed to four salinity levels (2, 4, 6, and 8 dS m−1). The results indicated that the exogenous application of KIO3 enhanced the yield, growth, and fruit characteristics of pepper plants under salinity stress. Notably, foliar spraying with 100 µM KIO3 resulted in higher levels of photosynthetic pigments, fruit dry matter content, fruit size, and membrane stability index by increasing non-enzymatic antioxidants, such as vitamin C, total phenolic content, and total soluble solids. Especially, 100 µM KIO3 enhanced leaf relative water content and fruit firmness while reducing fruit juice electrical conductivity compared to 0 and 50 µM KIO3 doses under saline conditions, indicating that KIO3 improved these traits to enhance the salinity resilience of pepper plants. Conclusively, these findings suggest that applying 100 µM KIO3 as a foliar spray is an effective and environmentally friendly method to enhance productivity and resilience in sweet pepper plants, helping to decrease the harmful impacts of salinity while improving overall quality.