Diversity of Arbuscular Mycorrhizal Fungi In Relation to Available P In Cassava Fields of Thailand.

Soil samples were collected from 305 cassava field across 41 provinces in Thailand and cassava cuttings were used to trap compatible arbuscular mycorhizal fungi (AMF). Bray II P and soil OM were measured. Soils where cassava had been planted varied widely in soil texture (sand to clay), and the pH ranged from acidic to alkaline (pH 3 - 8). Soil OM in cassava fields ranged from 0.3-6.2% and the available P ranged from 0.06 – 583 mg kg^-1. There was a highly significant (r² = 0.12**; n = 305) relationship between AMF spore number and available P and between soil OM and available P  (r² = 0.10**; n = 305).   The AMF genera trapped in cassava soil were Acaulospora, Entrophospora, Gigaspora, Glomus and Scutellospora. Roots of cassava cuttings were well-colonized by AMF (30 - 85% root length). Two genera of AMF, Glomus and Acaulospora, dominated spore number and root colonization in soils with high available P.