Evaluation of the Presence of Arbuscular Mycorrhizae and Cadmium Content in the Plants and Soils of Cocoa Plantations in San Martin, Peru

Abstract

Cocoa (Theobroma cacao L.) is an important crop in Peru. International regulations require products derived from cocoa to be free of heavy metals (HMs), such as cadmium. Arbuscular mycorrhizae (AM) contribute to reduced HM content in the plant, preventing its accumulation in the fruit and facilitating the rhizodeposition of HMs through glomalin-related soil proteins (GRSP). We studied the presence of mycorrhizal symbiosis in cocoa plants and cadmium in three plantations in San Martín, Peru. The maximum Cd content detected in soils was 1.09 (mg/kg), an amount below the tolerable limit for agricultural soil (≥1.4 mg/kg). Cocoa roots showed 68–86% active mycorrhizal colonization; agronomic management did not cause differences between plantations. Levels of GRSP were between 7.67 (GRSP-EE) and 13.75 (GRSP-T) mg protein g soil−1. Morphological and molecular analysis of Glomeromycota fungi showed the presence of families Claroideoglomeraceae, Paraglomeraceae, Gigasporaceae, Glomeraceae, Acaulosporaceae, Archaeosporaceae, and Diversisporaceae. Our results show the presence of arbuscular mycorrhizal symbiosis in cocoa plantations and suggest that T. cacao may phytostabilize HM in its rhizosphere through the production of GRSP. The presence of mycorrhizal symbiosis indicates the potential for the preparation of biofertilizers for cocoa since the production of GRSP is promissory for the biostabilization of soil HMs.

Arbuscular Mycorrhizal Fungi Associated with Myrciaria dubia in the Amazonia Region, Peru

“…Root colonization by AMF is characterized by presenting fungal structures, such as mycelium, auxiliary cells, arbuscules, vesicles, and spores [18,19], being this vast structure it is most important for its correct identification using the morphological approach [18][19][20][21][22]. Currently, in the Peruvian Amazon, some studies have recorded a great diversity of AMF [23][24][25][26][27]. New species were identified in different crops [23,[28][29][30][31][32][33][34][35][36][37][38] using morphological and molecular tools [39][40][41], and molecular analyses of the SSU-ITS-LSU region of rDNA [42].…”