Arbuscular Mycorrhizae in Cocoa Plantations that Bioaccumulate Cadmium

In recent years, Peru has become an important exporter of cocoa (Theobroma cacao L.); for this reason producing organic cocoa is significant for farmers. Cocoa plantations grow in acid soils with medium content of organic matter and phosphorus. Although Cd content levels in soil are below accepted levels established by the Environmental Quality Standards (1,4 ppm), certain cocoa varieties could bioaccumulate it in leaves and seeds. Arbuscular mycorrhizae (AM) have the ability to alleviate the toxicity of Cd in the plant by phytoextraction and / or phytostabilization. In order to use arbuscular mycorrhizae in cocoa plantations with the aim of alleviating Cd content, a diagnosis of the presence of AM symbiosis in organic plantations of San Martín with several cocoa varieties was made. Cocoa plants showed 21% of AM colonization in average, rhizospheric soil had 251 Glomeromycota spores / 100 g of soil, predominating genera from Gigasporaceae family. Cd levels detected were 1,58-2 ppm in leaves and 0,3-0,63 ppm in seeds. Rhizospheric soil samples were placed in traps pots with Brachiaria decumbens as host plant, to reproduce Glomeromycota spores and obtaining inocula of native fungi. Glomalin and extraradical mycelium of Glomeromycota fungi are correlated and related with the capacity of these fungi to alleviate toxicity of Cd in plant. The potentiality of arbuscular mycorrhizae in alleviating Cd toxicity in peruvian cocoa plantations management is discussed.