Long-term phosphorus fertilization effects on arbuscular mycorrhizal fungal diversity in Uruguayan grasses

Arbuscular mycorrhizas (AM) are particularly relevant in grasslands due to the high colonization in grasses, main constituent of this ecosystem. Natural grassland (NG) is the dominant ecosystem of Uruguay and it supports one of the main economic activities of the country: livestock. Available phosphorus (P) contents in NG soils of Uruguay are low, so phosphate fertilization is frequent. The aim of this work was to study the effect of phosphorus fertilization on arbuscular mycorrhizal fungi (AMF) diversity of two native grasses of Uruguay: Paspalum dilatatum and Coelorhachis selloana. Diversity and abundance of AMF spores in the rhizosphere of grasses were studied using morphological techniques, while AMF diversity in roots was studied through TRFLP. The study was conducted in a long-term experiment of phosphorus fertilization in Uruguayan grasslands. The increase in available P did not affect the diversity of AMF in the roots or in the rhizosphere of the studied grasses. The richness of AMF biotypes in roots and spores abundance differed between host species, with higher values in C. selloana than in P. dilatatum. Differences in AMF diversity between seasons were observed, with greater number of biotypes in winter than in summer.