Abundance and diversity of arbuscular mycorrhizal fungal (AMF) spores isolated from the rhizosphere of papaya and other different cropping systems in Central Kenya

Arbuscular mycorrhiza fungi (AMF), obligate symbionts, are important in the majority of cultivated plant species in colonizing roots and supporting plant growth in adverse climatic conditions. However, the abundance and quality of mycorrhizal colonization is affected by land-use types, cropping systems and climate change. On the other hand, rhizospheric mycorrhizae present in rhizospheric soils can be isolated for enhancing plant performance. One such opportunity arises in the acclimatization of seedlings for adaptation to depleted field conditions. Isolation and characterization of rhizospheric AMF species is important in evaluating the efficiency of colonization especially in plants that have not been previously evaluated such as papaya, which is well known for its high nutritive value. In this study, soils were sampled from grass, banana and papaya plants’rhizosphere, from three different papaya growing regions in Kenya; Mwea, Mitunguu and Juja. Spores were isolated using the sucrose method. Spore abundance was done using a gridded Petri dish and morphologically characterized using the International Culture Collection of Vesicular Arbuscular Mycorrhizal Fungi (INVAM) database. At least 4 families, 10 genera and 41 species of glomeromycota phylum were isolated from the 3 sampling sites. The families of glomeraceae (16 species) and acaulosporaceae (14 species) dominated in Juja and Mwea Sub Counties. Glomus spp. isolated from the rhizosphere of banana and grass plants were the most abundant, at p≤0.05, in Juja while Diversispora spp (diversisporaceae) was the least abundant, at p≤0.05. Mwea Sub County had the most spore abundance, at p≤0.05, compared to Mitunguu and Juja. Mycorrhizal spores isolated from the grass family were the most abundant, at p≤0.05, (Mwea, 41; Juja, 37; Mitunguu, 35.2) as opposed to banana and papaya plants. The results showed that AMF spore abundance and diversity varies with different locations and the associating plants.