Abstract
The tripartite associations of arbuscular mycorrhizal fungi (AMF), rhizobia and legumes play a vital role in preserving and even restoring fertility of poor and eroded soils. The present study attempted to quantify relationship between legumes and symbiotic microorganisms (rhizobia and mycorrhizal fungi) by describing the mycorrhizal status and the occurrence of nodualtion of legumes growing in different areas of Jazan. The effect of legume species on soil microbial biomass was also investigated. Mycorrhizal and nodulation intensity varied greatly between legume species. The higher number of nodules (14 nodules per plant) and mycorrhization intensity (54%) were registered in root of Argyrolobium arabicum. Rhizosphere soils of all legume species harbored higher AMF fungal spores than bulk soils. Our results suggest also a significant effect of legumes species on soil microbial biomass. Thus, legume species investigated in this study are potentially useful for replanting and soil protection of most degraded regions of Saudi Arabia.