Mycorrhizal symbioses, which are widespread in various terrestrial ecosystems, constitute a very important research topic for many biologists. Arbuscular mycorrhizal fungi (AMF), belonging to the phylum Glomeromycota, take their name from their characteristic structures: arbuscules. Spores represent the main structures allowing the morphological identification and characterization of AMF. The spores directly extracted from soil samples were identified under an optical microscope. The diversity of AMF in maize rhizospheres in Bouaflé and Niellé areas was highlighted. Thus, 12 genera of AMF divided into 8 families have been identified. Spores of two families of endomycorrhizae (Glomeraceae and Acaulosporaceae) have been described. The spores of the Glomeraceae family represented by 4 genera Glomus, Funneliformis, Septoglomus and Rhizophagus are globose to subglobose, 45 to 200 µm in size. The spores have a single wall composed of 3 to 4 parietal layers. The outer layers stain with Melzer's reagent. The suspensory hypha often characterized by the presence of constriction, light brown in color is the extension of layer 2. Morphologically, the spores of Acaulosporaceae represented by a single genus Acaulospora, are distinguished by the globose to subglobose shape. The spores are whitish, pale yellow, golden yellow to orange-brown in color and 90 to 200µm in diameter. The subcellular structure of spores consists of a spore wall (outer wall) and two inner walls. The outer and inner walls of the spores consist of three parietal layers. The outermost layers are evanescent, hyaline whitish, orange-brown to pale yellow. The layers of the inner wall are adherent to each other appearing as a single layer. The surface of the spores, populated with projections of different shapes resembling often rudimentary hyphae, show scars and ornamentations. This study gives the essential of the status of AMF and revealed the morphometric and structural characteristics of some AMF.

The overall objective of this study is to identify the physico-chemical properties influencing seasonal variations in chlorophyll-a levels and to assess the trophic status of the Napié reservoir in northern Côte d'Ivoire. The physico-chemical properties were determined in situ using a multiparameter instrument (HANNA 928) between 6 a.m. and 7:30 a.m. At four stations, water samples were collected monthly during the dry season (January, March, and April 2024) and the rainy season (June, July, and October 2024). Nutrient and chlorophyll-a levels were also analyzed. The results show that water is moderately warm, with moderately basic pH values and high nutrient levels during the dry season. Our hierarchical dendrogram shows three distinct groups of stations based on physico-chemical properties. Chlorophyll-a levels varied seasonally, with the highest levels recorded during dry seasons (81.9–275.33 μg/L) and the lowest during rainy seasons (40.9–86.20 μg/L). Regression analysis revealed both positive and negative associations between chlorophyll-a biomass and various physico-chemical properties. The trophic assessment, based on chlorophyll-a levels and the Organization for Economic Cooperation and Development classification system, indicates that the Napié reservoir is hypereutrophic, raising concerns about water quality and highlighting the need for sustainable management of this aquatic ecosystem.

Understanding the diversity of arbuscular mycorrhizal fungi (AMF) and identifying the main factors influencing their variation in soils is critical for characterizing crop production sustainability levels. AMF play a pivotal role in enhancing plant nutrient uptake and resilience to biotic and abiotic stresses, but little is currently known about their diversity in West African cocoa agroecosystems, particularly in Côte d'Ivoire. This observational study aimed to assess AMF diversity and abundance in cocoa rhizospheres and their relationship with soil chemical properties at five distinct sites in Côte d’Ivoire: Adzopé, Agnibilékrou, Azaguié, Biankouma, and Soubré. Soil samples were collected from 47 existing cocoa plots across these sites, and AMF spores were extracted and identified based on morphometric and structural criteria. The results revealed that the soils were acidic across all 47 cocoa plots, with significant regional variations in P levels and metal concentrations. Biankouma exhibited the highest levels of iron, aluminum, manganese, lead, and copper, whereas the soil P level was highest at Azaguié and lowest at Biankouma. Nineteen AMF genera were identified, with Acaulospora and Glomus being the most abundant across all sites, followed by Funneliformis, confirming the high ecological plasticity of these genera, which enables them to occupy diverse habitats. Despite significant spatial variations in spore abundance, AMF alpha diversity indices showed no statistically significant differences across the study sites. Soil acidity and elevated concentrations of specific metals negatively influenced AMF spore abundance. Furthermore, redundancy analysis indicated that the measured soil chemical properties collectively explained 29% of the AMF community structure variation, with chromium (Cr) emerging as the sole statistically significant environmental filter. This study highlights that a clear understanding of AMF communities in cocoa rhizospheres is essential to facilitate the design of efficient soil and plant conservation strategies, thus ensuring the sustainability and long-term productivity of cocoa agroecosystems in Côte d’Ivoire.

The assessment of diversity, spore abundance, and the understanding of environmental factors underlying the distribution of arbuscular mycorrhizal fungi (AMF) communities are fundamental themes in ecology. However, the diversity of AMF communities in maize rhizospheres within African tropical ecosystems, particularly in Côte d’Ivoire, remains poorly understood. AMF are obligate biotrophs that form symbiotic associations with plant roots, thereby improving host water and mineral nutrient acquisition and enhancing tolerance to both biotic and abiotic stresses. This study aimed to assess the diversity and abundance of AMF in maize rhizospheres and to examine their relationships with soil chemical properties across four study areas in Côte d’Ivoire: Bouafle, Bouake, Ferke, and Nielle. For this purpose, soil samples were collected from 20 maize rhizospheres, and AMF spores were extracted and identified based on morphological criteria. Chemical analyses of the maize rhizosphere soils indicated that the soils were generally slightly acidic across all 20 sampled rhizospheres. Significant variations were observed in the concentrations of phosphorus (P), calcium (Ca²⁺), and potassium (K⁺) among the study areas. Twelve families of AMF were identified across the study areas, with the Acaulosporaceae and Glomeraceae families being the most dominant. Variance partitioning showed that rhizosphere soil chemistry explained 69 % of the variation in AMF community composition, with P, CEC and K+ being the main drivers. These findings provide insights into the AMF composition in maize rhizospheres and highlight the role of soil chemical variables as key predictors of AMF diversity. Keywords: AMF communities, Maize rhizosphere, Soil properties