Grafting Alleviates Cadmium Toxicity and Reduces Its Absorption by Tomato

A pot experiment was conducted to determine whether the grafting could improve growth and reduce cadmium (Cd) accumulation of tomato planted in Cd-contaminated soil. ‘Zhongyanhong 6’ (common tomato) and ‘Hongyu F1’ (cherry tomato) were grafted onto two varieties of wild eggplant (Solanum torvum and Totosga) and three varieties of tomato (‘Dalishengen’, ‘Banzhen18’, and ‘Guozhen 1’) rootstocks, respectively, and then transplanted in 10 mg kg−1 Cd-contaminated soil for 3 months. The results indicate that except for Totosga, grafting onto other rootstocks resulted in decreased growth and biomass of ‘Zhongyanhong 6’, but grafting increased growth and biomass of ‘Hongyu F1’, especially wild eggplant. Compared with un-grafted, grafting on ‘Guozhen’, Solanum torvum, and Totosga enhanced weight and size of two types of tomato fruits under Cd stress, but only S. torvum improved soluble sugar content and soluble solids of tomato fruits. The Cd content in plants and fruits of ‘HongyuF1’ grafted on five rootstocks was reduced, and only grafted on ‘Banzhen18’, Solanum torvum, and Totosga reduced Cd content in plants and fruits of ‘Zhongyanhong6’, especially two kinds of wild eggplant rootstocks had the most significant reduction in Cd content. Therefore, grafting on different rootstocks had different impacts on two types of tomato under Cd stress, and wild eggplant especially S. torvum is relatively better rootstock for both types of tomato.