Acaulospora rugosa J.B. Morton, Mycologia

Pereira, Camilla M. R., Maia, Leonor C., Sánchez-Castro, Iván, Palenzuela, Javier, Silva, Danielle K. A., Sudová, Radka, Kolaříková, Zuzana, Rydlová, Jana, Čtvrtlíková, Martina, Goto, Bruno T., Silva, Gladstone A. & Oehl, Fritz, 2016, Acaulospora papillosa, a new mycorrhizal fungus from NE Brazil, and Acaulospora rugosa from Norway, Phytotaxa 260 (1), pp. 14-24 : 20

Acaulospora rugosa J.B. Morton, Mycologia 78 (4): 645. 1986. ( Figs 12–20 )

MycoBank MB 102995

Sporiferous saccules hyaline, formed at the end of mycelial hyphae. Saccule termini globose to subglobose, 90–125 × 85–118 Μm, with 1–2 wall layers (1.3–2.8 Μm thick). Saccule necks 18–32 Μm broad at the saccule termini tapering to 6–14 Μm towards the mycelium. Spores form laterally on the saccule necks, in 60–140 Μm from the saccule termini. They are yellow white to light yellow (straw), globose to subglobose, (49–)71–110(–120) × 68–108(–115) Μm, and have three walls. Outer wall consists of three layers (OWL1–OWL3). OWL1 hyaline to subhyaline, 0.7–1.7 Μm thick, evanescent to semi-persistent and has a wrinkled (rippled) surface due to the presence of innumerous folds (2–10 Μm in depth, 5–30 Μm in length, and an irregular distance to each other). OWL1 sometimes ballooning, and thus partly or completely separating from OWL2. OWL2 yellow-white to light yellow (straw), laminated, 1.3–3.8 Μm thick. OWL3 concolorous with OWL2, about 0.5–1.0 Μm thick. None of the OW layers stains in Melzer’s reagent. Cicatrix on OWL2 and by OWL3 is 6.0–11 Μm wide. Middle wall hyaline, bi-layered and 1.0–1.7 Μm thick. MWL1 and MWL2 are tightly adherent to each other. None of the MW layers stains in Melzer’s reagent. Inner wall is hyaline, with two to three layers. IWL1 is about 0.5–1.1 Μm thick with a ‘beaded’, granular structure that often disappears in lactic acid-based mountants. IWL2 is 1.0–2.5 Μm thick and regularly stains pinkish purple to dark purple in Melzer’s reagent. IWL3 is very thin (<0.8 Μm). Mycorrhiza formation with arbuscules, vesicles, and intra- and extraradical hyphae that stain dark blue in 0.05% trypan blue.

Distribution: — Acaulospora rugosa was originally discovered in strongly acidic rhizosphere soil of Andropogon virginicus in an abandoned coalmine in West Virginia ( USA, Morton 1986). The current population was recovered from acidic rhizospheric sediments of Drivenesvatn Lake (southern Norway), dominated by Lobelia dortmanna and Isoëtes echinospora .

Material examined — NORWAY, Vest-Agder, Drivenesvatn Lake (58.1732 N 7.5546 E) ; collected from a single species culture, 8 April 2013, R. Sudová and F. Oehl ( ZT Myc 55212, at Z + ZT) .

Molecular and phylogenetic analyses: —Molecular analyses and phylogenetic results place A. rugosa close to A. delicata ( ITS; Fig. 10 ) and A. mellea ( LSU; Fig. 11 ). The BLASTn analysis of the LSU rDNA fragment revealed several environmental sequences close to A. rugosa . Sequences from Miscanthus sinensis and Lotus japonicus roots collected in Hokkaido, Japan ( An et al. 2008, Cheng et al. 2013), presented 99% ( AB 369791) and 98% of similarity ( AB 369788, AB369790, AB369792, AB 547184). Sequences from Hedera rhombea and Rubus parvifolius roots ( Ahulu et al. 2006, 2007) also were close to A. rugosa (98% of similarity). ITS sequence data from aquatic macrophyte roots ( AM 420373, AM 420378) collected in the Netherlands ( Baar et al. 2011) had 97–98% similarity to A. rugosa .

Figures

FIGURE 10. Phylogenetic tree of the Acaulosporaceae obtained by analysis from ITS1, 5.8S rDNA and ITS2 sequences of Acaulospora spp. Sequences are labeled with their database accession numbers. Support values (from top) are from maximum parsimony (MP), maximum likelihood (ML) and Bayesian analyses, respectively. Sequences obtained in the current study are in boldface. Only support values of at least 50% are shown. Thick branches represent clades with more than 90% of support in all analyses. The tree was rooted by Claroideoglomus etunicatum (Consistency Index = 0.51; Retention Index = 0.87).

FIGURE 11. Phylogenetic tree of the Acaulosporaceae obtained by analysis from partial LSU rDNA sequences of Acaulospora spp. Sequences are labeled with their database accession numbers. Support values (from top) are from maximum parsimony (MP), maximum likelihood (ML) and Bayesian analyses, respectively.Sequences obtainedin the current study are in boldface.Only support values of at least 50% are shown. Thick branches represent clades with more than 90% of support in all analyses. The tree was rooted by Claroideoglomus etunicatum (Consistency Index = 0.49; Retention Index = 0.86).

FIGURES 12–20. Acaulospora rugosa. 12–13. Spores with rugose outer spore surface due to the wrinkling to rugose outer spore wall layer, which often shows several folds. 14–16. Outermost wall layer clearly separating to ballooning in spores receiving increasing pressure on the cover slides. 17. Rugose, folded structure of the outer wall layer on a crushed spore. 18. Crushed spore with three spore walls (outer, middle, inner wall: OW, MW, IW). 19–20. Spore segments of crushed spores in PVLG+Melzer’s reagent showing multiple layers of the three walls: OWL1–2, MWL1–2, IWL1–2. OWL1 clearly separating from OWL2; MWL1 locally separating from MWL2; IWL1 with ‘beaded’, granulate structure and IWL2 staining purple to dark purple in Melzer’s reagent.