Glomus rugosae Błaszk., B.T. Goto et Niezgoda, 2024

Błaszkowski, Janusz, Zubek, Szymon, Milczarski, Paweł, Malinowski, Ryszard, Goto, Bruno Tomio & Niezgoda, Piotr, 2024, Glomus rugosae, a new arbuscular mycorrhizal species in Glomeraceae (phylum Glomeromycota) from maritime sand dunes of Poland and an ash pond of Czech Republic, Phytotaxa 644 (4), pp. 271-280 : 274-276

Glomus rugosae Błaszk., B.T. Goto et Niezgoda , sp. nov. Figures 2A–H .

MycoBank No. MB 853099

Etymology: Latin, rugosae , referring to the plant species, Rosa rugosa , under which this species was originally found.

Typification: POLAND. Spores from a single-species culture established from spores extracted from a trap culture inoculated with a field-collected mixture of rhizosphere soil and root fragments of Rosa rugosa from a maritime sand dune site located near Kuźnica , Hel Peninsula, Poland (54°44′04″N 18°34′54″E), 2 May 2022, J. Błaszkowski (holotype slide with spores no. ZT Myc 0067314 , isotype slides with spores no. 3969–3978 , LPPDSE) .

Diagnosis: Differs from G. macrocarpum , the closest phylogenetic relative ( Fig. 1 , Figs. S1 , S 2 ), in: (i) the spore wall and subtending hyphal wall structure, (ii) morphometric features of spores, the spore and subtending hyphal wall, as well as (iii) nucleotide composition of sequences of the 45S nuc rDNA region and the rpb1 gene. Differs from G. spinuliferum , the only not sequenced glomoid spore-producing species having a four-layered spore wall in (i) spore colour, (ii) morphometric features of spores, subtending hyphae and the spore wall, and (iii) the phenotypic and histochemical properties of spore wall layers 2 and 1, respectively (see Discussion for details).

Description: Glomerospores (= spores) formed in soil, in loose clusters with 2–21 spores or singly, arise blastically at tips of (i) sporogenous hyphae branched from a parent hypha continuous with an extraradical mycorrhizal hypha (spores in clusters) or (ii) sporogenous hyphae directly continuous with extraradical mycorrhizal hyphae (single spores; Fig. 2A, F, G ). Spores pale yellow (4A3) to greyish yellow (4B3); globose to subglobose; (25–)62(–100) µm diam; rarely ovoid; 70–98 × 81–110 µm; with one subtending hypha ( Fig. 2A–G ). Spore wall composed of four layers ( Fig. 2B–F ). Layer 1, forming the spore surface, uniform (not containing visible sublayers), mucilaginous, short-lived, flexible, hyaline, (0.6–)0.7(–0.8) µm thick, often highly swelling/expanding in spores mounted in PVLG and separating from the upper surface of spore wall layer 2 by up to 15 µm, frequently entirely sloughed off in mature spores ( Fig. 2C–F ). Layer 2 uniform, permanent, smooth, semi-flexible, hyaline, (0.5–)0.8(–1.3) µm thick, tightly adherent to the upper surface of layer 3, not separating from this layer in even vigorously crushed spores ( Fig. 2C–F ). Layer 3 laminate, permanent, smooth, semi-flexible to semi-rigid, pale yellow (4A3) to greyish yellow (4B3), (0.8–)1.5(–3) µm thick, consisting of very thin, <0.5 µm thick, laminae, tightly adherent to and not separating from each other in even vigorously crushed spores ( Fig. 2B–F ). Layer 4 uniform, permanent, smooth, semi-flexible to semi-rigid, yellowish white (4A2) to pale yellow (4A3), (0.5–)0.6(–0.8) µm thick, tightly adherent to the inner surface of layer 3 in moderately crushed spores, occasionally separating slightly and locally from this layer in vigorously crushed spores ( Fig. 2B–F ). In Melzer’s reagent, only spore wall layer 1 stains reddish white (7A2) to pale red (8A3) ( Fig. 2C–F ). Subtending hypha pale yellow (4A3) to greyish yellow (4B3); straight or recurved, cylindrical to slightly funnelshaped, rarely slightly constricted at the spore base; (7.6–)9.8(–13.7) µm wide at the spore base ( Fig. 2A, F, G ); not braking in crushed spores. Wall of subtending hypha pale yellow (4A3) to greyish yellow (4B3); (1.7–)2.7(–3.8) µm thick at the spore base; consisting of four layers continuous with spore wall layers 1–4; subtending hyphal wall layer 1 swelling in PVLG and usually highly deteriorated or, occasionally, entirely sloughed off in mature spores ( Fig. 2F, G ). Pore (1.6–)4.8(–8.6) µm wide at the spore base, open, rarely closed by a curved septum connecting the inner surface of spore wall layer 4 ( Fig. 2A, F, G ). Spore content of hyaline oily substance. Germination unknown.

Ecology and distribution: In the field, Glomus rugosae probably lived in arbuscular mycorrhizal symbiosis with roots of Rosa rugosa , but no molecular analyses were performed to confirm this assumption. In single-species cultures with Plantago lanceolata as the host plant, G. rugosae formed mycorrhiza with arbuscules, vesicles, as well as intra- and extraradical hyphae that stained clearly [violet white (18A2) to blackish blue (19F8)] in 0.1% trypan blue ( Fig. 2H ). Phylogenetic analyzes with the 45S alignment used in this study and environmental sequences with>96% identity to 45S sequences of G. rugosae , revealed by BLASTn, indicated that G. rugosae was previously recognized in roots of Acer platanoides L., which grew in the ash sedimentation pond in Melnik, Cetral Bohemia, Czech Republic (data not shown). The environmental sequences that clustered with 45S sequences of G. rugosae were HG425911 and HG425912, with query covers = 100% and identities = 97.54% and 97.29%, respectively.

Figures

FIGURE 1. 50% majority-rule consensus tree from the Bayesian analysis of sequences of 45S nuc rDNA concatenated with rpb1 sequences of Glomus rugosae, six other Glomus species, and two Complexispora species serving as outgroup. The new species is in bold font. The Bayesian posterior probabilities ≥0.90 and ML bootstrap values ≥50% are shown near the branches, respectively. Bar indicates 0.02 expected change per site per branch.

FIGURE 2A–H. Glomus rugosae. A. Cluster with sporogenous hyphae (h), spores (sp), and a spore subtending hypha (sh). B–F. Spore wall layers (swl) 1–4. F, G. Subtending hyphal wall layers (shwl) 1–4 continuous with spore wall layers (swl) 1–4. H. Arbuscule (a), intraradical hyphae (ih), and vesicle (v) in Plantago lanceolata root stained in 0.1% Trypan blue. A, B, G, H. Spores and mycorrhizal structures in PVLG. C–F. Spores in PVLG+Melzer’s reagent. A–H. Differential interference microscopy. Scale bars: A = 20 μm, B–H = 10 μm.