Effects of Magnesium Addition on Yield, Quality and Cadmium Accumulation in Pepper Under Cadmium Stress

To investigate the effects of exogenous magnesium (Mg) addition on cadmium (Cd) accumulation, yield, and quality of pepper under Cd stress, two pepper cultivars, Hongtianhu 101 and Yuefeng 750, which differ greatly in their Cd accumulation capacities, were used as experimental materials. Based on Hoagland nutrient solution, three treatments were established: Cd treatment, Cd + Mg treatment, and a control treatment without Cd or Mg addition (CK). A seedling-stage hydroponic experiment and a pot experiment from the seedling stage to the mature stage were conducted using Hoagland nutrient solutions with different formulations. Indicators including dry matter production, yield, fruit quality, and Cd content in different organs of pepper were systematically determined. The results showed that, compared with the CK treatment, Cd treatment significantly decreased the photosynthetic pigment content, total dry matter weight, and yield at the mature stage, while significantly increasing leaf oxidative stress, Cd accumulation in different organs, and total Cd accumulation, accompanied by reduced fruit quality. However, Mg addition under Cd stress (Cd + Mg treatment) effectively increased the photosynthetic pigment contents and total dry matter weight at the mature stage, resulting in a significant increase in yield of 49.7–54.9%. Meanwhile, Mg addition reduced Cd accumulation in all plant organs, thereby significantly decreasing the total Cd accumulation by 17.2%–58.0%, markedly alleviating the degree of leaf oxidative stress, and improving pepper quality. Nevertheless, none of the above indicators fully recovered to the levels observed in the CK treatment. In summary, Mg addition under Cd stress alleviated the adverse effects of Cd stress in pepper plants, as indicated by improved growth performance, reduced Cd accumulation, and enhanced fruit quality. This study provides a theoretical basis for the production of high-yield and high-quality peppers in Cd-contaminated areas.