Soil depth: an overriding factor for distribution of arbuscular mycorrhizal fungi

Present study deals with the distribution and diversity of arbuscular mycorrhizal fungi (AMF) in naturally growing Withania somnifera and Ocimum sanctum. Variations in soil pH and moisture content (%) at different soil depths (0-10, 10-20, 20-30 and 30-40 cm) and their possible influences on AMF spore populations were studied at two sites i.e. Jaitpur and Karaiya. A total of 27 AMF species (8 Acaulospora, 1 Cetraspora, 1 Claroideoglomus, 1 Entrophospora, 1 Funneliformis, 13 Glomus, 1 Simiglomus and 1 Septoglomus) were identified. Results revealed that W. somnifera harbors relatively more AMF species (21) than O. sanctum (14). Acaulospora scrobiculata, Sep. deserticola and Sim. hoi dominated the rhizosphere of W. somnifera, while A. scrobiculata, Sep. deserticola and G. fasciculatum were predominant in O. sanctum. Spore populations, soil pH and moisture content varied significantly across soil depths. Moreover, the ability of soil to support AMF population decreased significantly with increased soil depth. Results clearly indicated the involvement of factor other than soil pH and moisture content in AMF distribution. Thus, it may be stated that overriding factor was depth, and this can be justified by fewer roots and fewer mycorrhizae in deeper soil layers.