Discovery of Arbuscular Mycorrhizae in Mosses of the Pottiaceae Family from the Chaco Serrano (Tucumán, Argentina)

Abstract

Arbuscular mycorrhizal fungi (AMF) are symbiotic fungi that associate with the vast majority of terrestrial plants. Among non-vascular plants, while AMF associations are well-documented in liverworts and hornworts, there is a broad consensus that symbiotic associations do not occur in mosses. Here, we report the presence of AMF in the living material of mosses found in Chaco Serrano (Tucumán, Argentina). We found all characteristic structures of AMF when establishing an intimate connection with two moss species of Pottiaceae (Bryophyta). While Gertrudiella uncinicoma exhibited AMF with both Arum- and Paris-type morphologies, Pleurochaete luteola only displayed an Arum-type morphology. Plant tissue samples were subjected to high-throughput sequencing for AMF identification. We determined that Rhizophagus irregularis was a clear dominant species in both moss species, with Glomus sp. also being present as a less abundant element. In addition, we also reported the presence of vesicles, arbuscules, and spores adhered to the hyphae and the presence of septate endophytes. This finding expands our understanding of the interactions between AMF and non-vascular plants and prompt us to further characterize this interaction by considering the diversity of mycorrhizal associations with concurrent implications for the ecology of mosses and the functionality of the ecosystems.

Keywords: AMF; Chaco Serrano; Glomus sp.; Rhizophagus irregularis; arbuscular mycorrhizal fungi; mosses; mycorrhiza.

Figure 1

Natural habitat and general aspect of the plants. (a) Habitat at Chaco Serrano Forest. (b) Gertrudiella uncinicoma. (c) Pleurochaete luteola.

Figure 2

Gertrudiella uncinicoma colonized by arbuscular mycorrhizal fungi. (a,b) Arum-type intracellular hyphae (IH) found in leaves. (c,d) Arum-type arbuscules (A) in the stem. (e) Arum-type hyphae in leaves (CH). (f) Paris-type (arrows) morphology in stems. (g) Arum-type (AT) morphology in stems (arrowed). (h,i) Vesicles (V) in leaves. (a,b,e,h,i) Light micrographs of samples stained with trypan blue. (c,d,f,g) Scanning electron micrographs. Scale bars are in each figure.

Figure 3

Gertrudiella uncinicoma colonized by arbuscular mycorrhizal fungi, and endophytic fungi. (a–c) Vesicles (V) in leaves. (d) Rhizoid with vesicles (V) and AMF hyphae (H). (e) Spores of Glomus sp in leaves. (f) Spores resembling representatives of Gigasporaceae were attached to a rhizoid. (g) Dark septate endophyte and microsclerotia (arrowed) in leaves. (h) Unknown septate fungus (arrowed) in leaves. (a,d–h) Light micrographs of samples stained with trypan blue. (b,c) Scanning electron micrographs. Except for panels (d,f), the rest of the observations were performed in leaves. Scale bars are in each figure.

Figure 4

Pleurochaete luteola colonized by arbuscular mycorrhizal fungi and endophytic fungi. (a–c) Arbuscules (A). (d,e) Vesicle (V). (f) Spores of Glomus sp. (g) Unknown septate fungus (arrowed). (d–g) Light micrographs. (a–c) Scanning electron micrographs. a-g were found in stems. (d–g) are trypan blue-stained samples. Scale bars are in each figure.