Acaulospora fanjing R.J. He, L.M. Yao & L. Jiang, 2021

He, Rong-Jian, Long, Chun-Li, Yao, Li-Mei & Jiang, Long, 2021, Acaulospora fanjing (Glomeromycota), a new species of arbuscular mycorrhizal fungi from Fanjingshan in China, Phytotaxa 524 (3), pp. 191-198 : 193

Acaulospora fanjing R.J. He, L.M. Yao & L. Jiang sp. nov. ( Figs. 1–9 )

Fungal Names FN570847

Sporiferous saccule unknown. Spores are formed singly in soils, reddish-brown to orange-brown, small oil droplets shine in the spores. Spore shape is globose to subglobose, (109–)123(–138) µm diam, rarely ovoid to irregular, (105–)125(–145) µm diam ( Fig. 1 ).

Outer spore wall consists of three layers (SWL1–SWL3), in total 2.5–4.0 µm thick ( Figs. 3–6 ). SWL1 forming the spore surface, evanescent, hyaline, (0.5–)1.0(–1.2) μm thick, usually absent in mature spores ( Fig. 3 ). SWL2 permanent, orange-brown to reddish orange, laminate, smooth, 2.0–3.5 μm thick. SWL3 concolorous with SWL2, 0.5–1.0μm thick, usually tightly adherent to SWL2 and often difficult to observe. None of these wall layers stains in Melzer’s reagent ( Figs. 3–6 ).

Middle wall is hyaline, semiflexible and thin, in total 0.7–1.5μm thick, bilayered tightly adherent (MWLl–MWL2), often appearing as being one wall layer. None of the layers reacts to Melzer’s ( Fig. 5 ).

Inner wall is hyaline, consists of three layers (IWLl–IWL3) and tightly adherent to each other, 1.5–3.0 μm thick in total ( Figs. 5–6 ). The IWL1 is flexible, about 0.5 μm thick, and not “beaded”structure; IWL2 is plastic, 0.9–1.5 μm thick; IWL3 is 0.4–1.0 μm thick and usually difficult to detect due to the close adherence to IWL2. Only IWL2 shows a pale pink reaction to Melzer’s reagent ( Fig. 6 ).

Cicatrix circular to subcircular, slightly raised collar, 8–11 µm wide ( Figs. 7–8 ). The pore is closed by inner laminae of SWL2 and SWL3.

Mycorrhizal associations:—In the field, A.fanjing was found associated with the rhizosphere of Acer flabellatum in Fanjing mountains from China. In single-species cultures with Trifolium pratense L as host plant, A.fanjing formed mycorrhiza with arbuscules, vesicles, and hyphae ( Fig.10 ).

Specimens examined:— China. Guizhou, National Nature Reserve of Fanjingshan (27°53’45”N, 108°43’15”W), in rhizosphere of Acer flabellatum in the ecotone (mossy dwarf forest) between habitats 1900m and 2300m, 22 Oct 2020. Holotype, herbaria CGMCC, voucher HMAS 281446 !

Etymology:— fanjing (Latin) , referring to the site of Fanjing Mountain in China, where this AMF species was recorded for the first time.

Distribution and habitat:—Spores of A.fanjing were isolated from rhizospheric soil of Acer flabellatum , whereby the records were located in the mossy dwarf forest of Fanjing Mountain . None of the SSU-ITS-LSU sequences obtained from BLAST queries had>97% similarity. Therefore, A.fanjing must be considered, at the moment, an AMF with a restricted area.

Figures

Figure 10. MrBayes and RAxML phylogram inferred from SSU-ITS-LSU sequence data. The Bayesian Analysis (BA) and Maximum Likelihood (ML) trees show the same phylogenetic topology, with A.fanjing as a new species that belongs to the genus Acaulospora. The tree is rooted with Claroideoglomus claroideum. Posterior probalities (>0.50) and maximum likelihood support values (>50) are showed on each branch (PP/MP). The new species is in bold.

FIGURES 1–9. Acaulospora fanjing spores. 1. Intact spores. 2. Crushed spore. 3–6. Spore wall layers (SW+MW+IW), SWL1 smooth, hyaline and evanescent and completely shed; SWL2 and SWL3 laminate and similar color, in some spores the boundaries between layers are difficult to distinguish; Middle wall (MWLl–MWL2) hyaline, semiflexible bilayered tightly adherent; Inner wall (IWL1–IWL3) hyaline, consists of three layers. Note: MW and IW are easily separated in PVLG and IWL2 shows a pale pink reaction to Melzer’s reagent. 7–8. Cicatrix circular to subcircular, slightly raised collar. 9. Mycorrhizal structures of A.fanjing in roots of Trifolium repens stained in 0.1% Trypan blue: hyphae (H) and vesicles (V). 3, 4, 6. In Melzer’s. 5. In PVLG+Melzer’s reagent.