Intercropping of <i>Cyphomandra betacea</i> with Different Ploidies of <i>Solanum</i> Sect. <i>Solanum</i> (Solanaceae) Wild Vegetables Increase Their Selenium Uptakes

Selenium (Se) deficiency causes various diseases in humans. Se can be obtained from fruits and vegetables. In this study, the fruit tree <i>Cyphomandra betacea</i> was intercropped with three <i>Solanum</i> sect. <i>Solanum</i> (Solanaceae) wild vegetables [diploid (<i>S. photeinocarpum</i>), tetraploid (colchicine-induced <i>S. photeinocarpum</i>), and hexaploid (<i>S. nigrum</i>)], respectively, and Se uptakes of these plants were determined by a pot experiment. Intercropping decreased the biomass, photosynthetic pigment content, and superoxide dismutase activity of <i>C. betacea</i>, but increased the peroxidase (POD) activity, catalase (CAT) activity, and soluble protein content of <i>C. betacea.</i> These indicators’ values of sect. <i>Solanum</i> increased after intercropping. The contents of Se increased in <i>C. betacea</i> and sect. <i>Solanum</i> after intercropping. Intercropped with diploid, tetraploid, and hexaploid increased the shoot Se contents in <i>C. betacea</i> by 13.73%, 17.49%, and 26.50%, respectively, relative to that of <i>C. betacea</i> monoculture. Intercropped with <i>C. betacea</i> increased the shoot Se contents in diploid, tetraploid, and hexaploid by 35.22%, 68.86%, and 74.46%, respectively, compared with their respective monoculture. The biomass and Se content of intercropped sect. <i>Solanum</i> showed linear relationships with the biomass and Se content of their monocultures. The biomass and Se content of intercropped <i>C. betacea</i> also exhibited linear relationships with that of sect. <i>Solanum</i> monocultures. Correlation and grey relational analyses revealed that the CAT activity, POD activity, and soluble protein content were the top three indicators closely associated with the <i>C. betacea</i> shoot Se content. The POD activity, soluble protein content, and translocation factor were the top three indicators closely associated with sect. <i>Solanum</i> shoot Se content. Therefore, intercropping can promote the Se uptake in <i>C. betacea</i> and sect. <i>Solanum</i> wild vegetables.