Cashew nut cultivation plays an important socio-economic role in Senegal. However, it suffers from several problems, including declining soil fertility which leads to low productivity. To overcome these constraints, the use of arbuscular mycorrhizal fungi (AMF) could be a sustainable alternative. However, the positive effects of AMFs may depend on their infectious potential, density, and diversity. So far, little attention has been given to exploring these aspects in cashew plantations. The proposal of this study is to determine the infectious propagules, density and diversity of AMF spores in cashew agro-systems. Soil samples were collected from four cashew production areas in Senegal (Ziguinchor, Sédhiou, Kolda and Fatick). The soil samples were previously treated by wet sieving and decantation technique and the spores were isolated by centrifugation; thereafter, a morphological identification of the extracted spores was carried out. To compare AMF propagule numbers between sites, a most probable number (MPN) bioassay was performed under greenhouse conditions using Zea mays as the host plant. The average AMF spore density was significantly higher in Ziguinchor (610 spores/100 g soil), Sédhiou (586 spores/100 g soil), and Fatick (445 spores/100 g soil) compared to Kolda (211 spores/100 g soil). However, no significant difference was noted between Ziguinchor, Sédhiou, and Fatick. Spore and propagule densities show opposite results, MPN was high in sites with low spore density. The identification of the spores showed 6 genera belonging to Glomus, Gigaspora, Acaulospora, Scutellospora, Entrophospora, and Racocetra. Identified AMFs could be isolated and multiplied to produce bioinoculants for cashew trees.
Key words: Abundance, Arbuscular mycorrhizal fungi, morphological diversity, most probable number, Anacardium occidentale, Senegal.
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