Screening Indigenous Arbuscular Mycorrhizal Resources for Subsequent Inoculum Production from Cassava, Maize, and Cocoa Rhizospheres in Daloa, Côte d’Ivoire

Abstract

Background: Arbuscular mycorrhizal fungi (AMF) represent valuable biological resources for the development of sustainable agriculture. However, the diversity and mycorrhizal potential of indigenous communities may vary among crops and agroecological conditions. Aims: This study aimed to screen and compare indigenous AMF resources associated with cassava, maize, and cocoa rhizospheres in the Daloa region, Côte d’Ivoire, with the objective of identifying candidate resources for subsequent AMF characterisation and multiplication. Study Design:  Greenhouse conditions in Daloa, Côte d’Ivoire. Place and Duration of Study: Jean LOROUGNON GUEDE University, Department of Plant Biology, between April and June 2023. Methodology: Rhizosphere soil and root samples were collected from cassava, maize, and cocoa fields and used as inocula in trap cultures with cowpea (Vigna unguiculata L.). Root mycorrhizal frequency and intensity, as well as spore density and AMF morphotype richness, were assessed.  Results: All inoculated trap plants were colonised by AMF, providing evidence for the presence of infective propagules in the three crop rhizospheres. However, mycorrhizal frequency and intensity varied among the different crop × inoculum type combinations. The maize-derived root inoculum showed the highest mycorrhizal frequency and intensity and the highest spore density (179 ± 217.5 spores/30 g soil), which was significantly higher than that of the other combinations. Factorial analysis revealed a significant effect of crop on spore density, whereas neither the main effect of inoculum type (root vs. soil) nor the crop × inoculum type interaction was significant. In contrast, the cassava-derived root inoculum exhibited the highest AMF morphotype richness (seven morphotypes). No detectable spores were recovered from the cocoa-derived inocula during the experimental period, despite the colonisation of cowpea roots. Conclusion: These results indicate that, under the conditions tested, infectivity, sporulation, and AMF morphotype richness do not necessarily follow the same pattern among indigenous resources. Thus, maize- and cassava-derived resources, particularly root inocula, can be considered as candidate starting materials for further AMF characterisation and multiplication studies.