Scion-rootstock interaction and tolerance to cadmium toxicity in juvenile Theobroma cacao plants

Abstract

Cadmium (Cd) is a highly toxic metallic element for plants, animals and humans. The presence of toxic metals in food has been a concern of the Food and Agriculture Organization of the United Nations. Several studies have demonstrated the presence of Cd in T. cacao beans and its by-products. The contents are found to be above the limits established by international authorities responsible for food safety. This study aimed to evaluate the toxicity of Cd in different genotypes of T. cacao, in scion-rootstock combinations (CCN 51/BN 34, CCN 51/PS 13.19, CCN 51/PH 16, CCN 51/CCN 51, BN 34/BN 34, PS 13.19/PS 13.19 and PH 16/PH 16). The combinations were grown in soil with 0, 75 and 150 mg Cd kg−1 soil. The measurements for evaluation were leaf gas exchange, activity of enzymes involved in antioxidant metabolism and lipid peroxidation. Cd promoted physiological and biochemical changes, in the scion-rootstock interaction, in juvenile T. cacao plants. The combinations CCN 51/BN 34 and CCN 51/PH 16 demonstrated tolerance to the toxicity of Cd in the soil, mainly evidenced by the higher accumulation of Cd in the root system, higher carbon assimilation, higher activity of superoxide dismutase, ascorbate peroxidase and catalase, lower lipid peroxidation and higher water use efficiency in the presence of Cd. The combination CCN 51/BN 34 shows promising potential to be grown in soils contaminated by Cd.