Arbuscular mycorrhizal fungal community shifts driven by heavy metals in cocoa agroecosystems at different crop age

Abstract

Cocoa (Theobroma cacao L.) is an economically important tropical crop, but its production is increasingly constrained by strict regulations related to heavy metal accumulation in soils. Arbuscular mycorrhizal fungi (AMF) are a key biological component of cocoa agroecosystems due to their role in soil processes and plant nutrition. However, information on AMF diversity and their response to heavy metals remains limited. In this study, AMF communities were evaluated in cocoa plantations of different ages established under contrasting heavy metal conditions. A total of 53 AMF taxa were identified, indicating high fungal richness across all plantations. No significant differences were found in α-diversity indices or community composition among plantation ages. In contrast, multivariate analyses showed that variation in AMF community structure was primarily associated with soil heavy metal gradients, particularly cadmium (Cd) and zinc (Zn). Species-level models revealed contrasting responses among taxa, with both positive and negative associations along Cd and Zn gradients, suggesting differential tolerance strategies. Overall, these results indicate that edaphic factors, especially heavy metal concentrations, play a more important role than plantation age in shaping AMF community composition. These findings provide a basis for identifying AMF taxa adapted to metal-enriched soils and for developing management strategies that support sustainable cocoa production.