Host preferences of arbuscular mycorrhizal fungi colonizing annual herbaceous plant species in semiarid Mediterranean prairies

Abstract

In this study, we have analyzed and compared the diversities of the arbuscular mycorrhizal fungi (AMF) colonizing the roots of five annual herbaceous species (Hieracium vulgare, Stipa capensis, Anagallis arvensis, Carduus tenuiflorus, and Avena barbata) and a perennial herbaceous species (Brachypodium retusum). Our goal was to determine the differences in the communities of the AMF among these six plant species belonging to different families, using B. retusum as a reference. The AMF small-subunit rRNA genes (SSU) were subjected to nested PCR, cloning, sequencing, and phylogenetic analysis. Thirty-six AMF phylotypes, belonging to Glomus group A, Glomus group B, Diversispora, Paraglomus, and Ambispora, were identified. Five sequence groups identified in this study clustered to known glomalean species or isolates: group Glomus G27 to Glomus intraradices, group Glomus G19 to Glomus iranicum, group Glomus G10 to Glomus mosseae, group Glomus G1 to Glomus lamellosum/etunicatum/luteum, and group Ambispora 1 to Ambispora fennica. The six plant species studied hosted different AMF communities. A certain trend of AMF specificity was observed when grouping plant species by taxonomic families, highlighting the importance of protecting and even promoting the native annual vegetation in order to maintain the biodiversity and productivity of these extreme ecosystems.

Fig 1

Maximum parsimony (MP) phylogenetic tree showing AM fungal sequences isolated from roots of H. vulgare, A. arvensis, S. capensis, C. tenuiflorus, A. barbata, and B. retusum and reference sequences from GenBank. All bootstrap values of >80% are shown (1,000 replicates). Numbers above branches indicate the bootstrap values of the MP analysis. Sequences obtained in the present study are shown in bold type. They are labeled with the host plant from which they were obtained (HIE, roots of H. vulgare; ANA, roots of A. arvensis; STI, roots of S. capensis; CAR, roots of C. tenuiflorus; AVE, roots of A. barbata; BRA, roots of B. retusum) and the clone identity number. Group identifiers (for example, Glo G1) are phylotypes found in our study. Endogone pisiformis and Mortierella polycephala were used as outgroups.

Fig 2

Sampling effort curves for the AM fungal community in the roots and rhizosphere soil of H. vulgare, A. arvensis, S. capensis, C. tenuiflorus, A. barbata, and B. retusum. The sample order was randomized by 100 replications in EstimateS, version 8.0 (12).

Fig 3

Bar plot showing the number of clones detected for each phylotype in the roots of H. vulgare, A. arvensis, S. capensis, C. tenuiflorus, A. barbata, and B. retusum.

Fig 4

Canonical correspondence analysis (CCA) of the AM fungal community composition found in the roots of H. vulgare, A. arvensis, S. capensis, C. tenuiflorus, A. barbata, and B. retusum. The eigenvalues of the x and y axes in the two-dimensional ordination diagrams are as follows: dimension 1, 0.39; dimension 2, 0.26. Open triangles indicate the respective phylotypes, and the filled triangles indicate the plant species.