The aim of this study was to evaluate the inoculation effect of arbuscular mycorrhizal fungi (AMF) of Brazilian pine plants (Araucaria angustifolia (Bert.) O. Ktze.) at different P levels. The experimental design was completely randomized with a factorial outlay of four inoculation and four P level treatments in five replications. The Araucaria plants, grown in greenhouse conditions, were inoculated either with Gigaspora rosea, with Glomus intraradices, or with a mixture of AMF, collected in a native Araucaria forest in Campos do Jordão, State of São Paulo, Brazil. The control treatment consisted in non-inoculated plants. Four P levels (0, 20, 50 and 150 mg kg-1 of P in the soil) were tested in the form of KH2PO4. Shoot and root dry matter, AMF root colonization, spore rates in the soil, and nutrient contents in the shoot were evaluated. The conclusion was drawn that Araucaria angustifolia is a mycotrophic plant which presents mycorrhizal dependency up to a P level of 150 mg kg-1 in the soil. Root colonization and sporulation rates varied according to the AMF species. Gigaspora rosea is indicated for soils with a low P level, and Glomus intraradices for higher P levels, while the native AM fungi are beneficial for Araucaria plant growth at all tested P levels. Mycorrhizal plants always presented higher P and lower N and K shoot concentrations than the non-mycorrhizal ones, independent of the AMF species.
Brazilian pine; mycorrhizal efficiency; mycorrhizal fungi; phosphate level