Phosphorus-responsive fungi associated with roots of uruguayan native grassland plants: a microcosm study with two herbs and two grasses

Temperate natural grasslands are threatened species-rich ecosystems on soils of low phosphorus (P) availability. Several fungi associate with roots and may facilitate P acquisition from recalcitrant pools. This work aimed at (i) unravelling mycobiota associated with four plant species, two herbs and two grasses, typical for Uruguayan grassland, (ii) determining whether P addition alters their abundance, and (iii) identifying abundant fungal genera under P-deficient conditions, and potentially mitigating P deficiency. A microcosm study with Adesmia bicolor, Bacharis genistelloides, Cyperus aggregatus, and Paspalum notatum with different P additions levels was set up. Shoot dry weight and P concentration in shoots were quantified. Root colonisation by mycorrhizal fungi and dark septate endophyte were assessed and ITS2 sequences from rhizosphere and root samples were analysed. Phosphorus addition increased the shoot dry weight of dicotyledonous species (herbs) and shoot P concentration of all plant species. Arbuscule colonization decreased with increasing P addition in all mycorrhizal plants. Fungal communities in the rhizosphere were more diverse and influenced by P addition, whereas communities in roots were shaped by plant species identity. A total of 31 fungal genera were found to be more abundant under P-deficiency conditions. Many are known to solubilize P. Most plant species shifted their root-associated mycobiota in the same direction in response to P addition. Penicillium and Rhizopus seem to be abundant root-associated mycobiota under plant P-deficiency.