Tolerance strategies and factors that influence the cadmium uptake by cacao tree

•Factors that influence Cd absorption by cocoa were soil pH, soil Cd availability and genotype.•The main strategy used by cocoa to reduce Cd toxicity is uptake and transfer of Cd and molecular changes.•CCN51 genotype had lower Cd concentrations than other genotypes. Cadmium (Cd) is a non-essential trace metal, highly toxic to plants, animals and humans. Its mobility in the soil is high and it is transferred with relative ease to crops. European Food Safety Agency (EFSA) has identified the consumption of chocolate as a source of Cd contamination, and established maximum Cd limits allowed in cacao-based products. Therefore, research related to tolerance and reduction of Cd toxicity in a cacao becomes important. The main objective of the present study was to systematize the main factors that interfere in the uptake of soil Cd by the cacao tree and its strategies for tolerance to toxicity. A systematic review of the literature was conducted using six databases for academic research (Google Academic, PubMed, Springer, CAPES Periodical, Scielo and Science Direct). To avoid publication bias, a previously established protocol and inclusion and exclusion criteria were used. The main factors related to the uptake of soil Cd by the cacao tree were soil pH, soil Cd availability, genotype, the geographical location, agronomic factors such as phosphate fertilizersand Cd interaction with other minerals/metal nutrients such as Zn and Mn present in the soil. To reduce the toxicity of this metal, cocoa promotes some tolerance strategies such as uptake and transfer of Cd from the root to the shoot, molecular and biochemical changes, Cd partition between plant organs and Cd sequestration at the cellular level. So, this systematic review contributed to the acquisition of knowledge for the genetic improvement of cacao tree, concerning toxicity tolerance strategies and reduction of soil Cd uptake.