Arbuscular mycorrhizal fungi diversity associated with Capsicum annuum var. glabriusculum in tropical soils

Tropical soils contain a high diversity of arbuscular mycorrhizal fungi (AMF), which play an essential role in plant nutrition and resilience. This diversity can vary depending on soil properties, the vegetation, and management practices. Therefore, characterising the abundance and diversity of AMF associated with culturally important plant species as well as their relationship with the edaphic properties of the soils in which they are found is crucial for understanding, conserving, and optimising plant productivity. This study aimed to characterise and compare the diversity and composition of AMF in the rhizosphere of Capsicum annuum var. glabriusculum (Dunal) Heiser and Pickersgill in tropical soils with varying physicochemical properties. Soil and rhizosphere root samples were collected from chili plants at 10 sites: six sites on Acrisols and four on Fluvisols. The AMF were identified based on spore morphology; the mycorrhizal colonisation was assessed in stained roots using optical microscopy, and the fungal diversity was analysed using Hill numbers (q₀, q₁, and q₂). Sampling coverage was 100%, with increases in q₀, q₁ and q₂ of 35.2%, 63.13% and 76.19%, respectively, in Acrisols compared to Fluvisols. Twenty-three species and morphospecies belonging to six families and seven genera were recorded; Acaulospora was the most diverse genus, and Glomus was the most abundant, with a relative abundance of up to 10%. The following species were found in both soil types: Acaulospora mellea, Funneliformis geosporum, Glomus sp.2, Glomus sp.3 and Rhizoglomus clarus. Total colonisation ranged from 90-100% in Acrisols to 80-87% in Fluvisols. In Acrisols, hyphae predominated in association with soil organic carbon, N, and B contents and the C/N ratio. In Fluvisols, arbuscules predominated in association with a neutral pH, CEC and Ca, P, Cu and silt contents. Evaluating the diversity of AMF in the rhizosphere of this chili enabled Acaulospora tuberculata to be recorded for the first time in Acrisols, thereby expanding the mycorrhizal inventory in humid tropical soils.