The mycorrhizal status of indigenous arbuscular mycorrhizal fungi of physic nut (Jatropha curcas) in Thailand

The dependence of physic nut (Jatropha curcas L.) on beneficial soil fungi for growth is not known. Therefore, the spore density and species diversity of arbuscular mycorrhizal fungal (AMF) associated with physic nut was assessed by extracting spores from physic nut plantings from 10 sites across 6 provinces in northern and north-eastern Thailand. Approximately 700 AMF spores, obtained using the wet sieving and sucrose gradient centrifugation methods, were identified into morphospecies. Colonization by AMF was assessed under a compound microscope using root samples stained with trypan blue. The following 34 morphospecies of AMF were identifed: Acaulospora (16 species), Entrophospora (1 species), Gigaspora (2 species), Glomus (10 species) and Scutellospora (5 species). The diversity index ranged from 0.28 to 0.86 (average 0.64) and the species richness of AMF ranged from 3 to 11 (average 6.2). Roots of physic nut were colonized by AMF at all sites sampled and infection levels ranged from 38 to 94% of root length. The presence of mycorrhizas in soils varying in pH from acidic to calcareous, of low to moderate organic matter and of low to high available P suggests that physic nut may be highly dependent on AMF.