Mycorrhizal Dependency and Response of Tomato ( Lycopersicon esculentum ) to Inoculation by Indigenous Arbuscular Mycorrhizal Fungi as Influenced by Available Soil Phosphorus Levels

A pot experiment was conducted on tomato (Lycopersicon esculentum) to evaluate the responses of tomato to inoculation of mycorrhiza (AMF) under different levels of soil phosphorus (P) concentrations in a greenhouse study. The results showed different responses on dry matter yield, shoot phosphorus concentration, mycorrhizal colonization and mycorrhizal dependency of the tomato plant. No evidence of AM fungal colonization was noted in the uninoculated soil. L. esculentum responded positively to AM fungus inoculation except at the two levels of soil P concentration (0.32 ppm and 0.92 ppm). Shoot dry matter, stem diameter and P concentration of the plant increased significantly in response to inoculation at the lowest three levels of soil P concentration (0.02, 0.04 and 0.12 ppm) as compared to the negative controls. The best response in all parameters was observed at the soil P concentration levels of 0.02 and 0.04 ppm. Levels of P concentration greater than 0.12 ppm suppressed AM fungi colonization. Soil P concentration levels of 0.32 and 0.92 ppm caused negative mycorrhizal dependencies (MD). The P level 0.32 ppm was found to be the cut-off value for positive response to inoculation of AM fungi in most of the tested parameters. Keywords : Arbuscular mycorrhizal fungi (AMF); Lycopersicon esculentum; Mycorrhizal colonization; Mycorrhizal dependency; P concentration levels. Ethiopian Journal of Biological Sciences Vol. 5 (2) 2006: pp. 147-159