Arbuscular mycorrhizal fungi community composition in Theobroma cacao is predominantly influenced by scion genotype and soil phosphorus availability

Community composition of arbuscular mycorrhizal fungi (AMF) is shaped by plant genotype, root traits, and environmental variables. Cacao ( Theobroma cacao ) is a mycotrophic agroforestry crop. Separately harnessing rootstock and scion genetic variation associated with AMF community composition could contribute to more sustainable cacao agroforestry systems. Our study aimed to: (1) characterize AMF communities in cacao roots, and (2) evaluate relationships between these communities and scion and rootstock genotypes, root traits, and soil properties. We sampled roots and soils from 81 trees in 16 Panamanian farms in the provinces of Bocas del Toro and Herrera. We analysed AMF communities, scion and rootstock genotypes, root traits (the four traits of the root economics space, plus root phosphorus concentration), and soil characteristics. Glomus was the dominant genus across all samples. Scion genotype, root nutrient concentration (N and P), elevation, and available P emerged as major variables structuring AMF communities, while rootstock genotype and root morphological traits did not. Our findings highlight the role of host and environmental variables in AMF community composition, informing strategies for sustainable cacao cultivation through optimized plant-fungal interactions.