Acaulospora papillosa C.M.R. Pereira & Oehl, 2016

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 : 16-20

Acaulospora papillosa C.M.R. Pereira & Oehl , sp. nov. ( Figs 1–9 )

MycoBank MB 814407

Holotype: — BRAZIL, Pernambuco, Tamandaré, ‘ Reserva Biológica de Saltinho’ (8.4334 S 35.1028 W), isolated from rhizospheric soil of a greenhouse pot culture and grown on Zea mays at UFPE in Recife , April 2015, C. M. R. Pereira ( URM 87964 ).

Sporiferous saccules hyaline, formed at the end of mycelial hyphae. Saccule termini globose to subglobose, 70–100 × 65–95 Μm, with 1–2 wall layers (1.3–2.6 Μm thick). Saccule necks 16–28 Μm broad at the saccule termini tapering to 6–12 Μm towards the mycelium. Spores form laterally on the saccule necks, 50–140 Μm from the saccule termini. They are yellow white to light yellow to creamy, globose to subglobose, 69–100(–110) × 65–93(–101) Μm, and have three walls. Outer wall consists of three layers ( OWL 1– OWL 3). OWL 1 hyaline to subhyaline, 0.7–1.7 Μm thick, evanescent to semi-persistent and has a roughened surface due to the presence of small papillae (0.5–1.1 Μm in diameter, 0.5–1.2 Μm high, and in 0.5–1.1 Μm distance to each other). OWL 2 yellow-white to light yellow to creamy, laminated, 1.7–4.3 Μm thick. OWL 3 concolorous with OWL 2, about 0.5–1.1 Μm thick. None of the OW layers stains in Melzer’s reagent. Cicatrix on OWL 2 and by OWL 3 is 7.0–10.8 × 6.5–8.7 Μm wide. Middle wall hyaline, bi-layered and 1.0–2.1 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 0.6–2.4 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 extra-radical hyphae that stain dark blue in 0.05% trypan blue.

Etymology: — papillosa refers to the papillae structure responsible for the rough appearance of the spore surface.

Habitat: —rhizospheric soil in Tropical Atlantic rainforest.

Distribution: —known only from the type locality.

Material examined: — BRAZIL, Pernambuco, Tamandaré, ‘Reserva Biológica de Saltinho’, June 2015, isotype ( URM 87965), isotype ( URM 87966), paratype ( URM 87967), paratype ( URM 87968) and isotype ( ZT Myc 55192).

Molecular and phylogenetic analyses: —The phylogenetic analyses from the ITS and LSU sequence data placed the new fungus in a separate clade within the Acaulosporaceae , close to A. longula ( LSU rDNA; Fig. 10 ) and A. morrowiae ( ITS rDNA; Fig. 11 ). The support values for the clade of the new species were above 75% in all analyses. For the whole ‘Krüger fragment’ ( Krüger et al. 2009), A. papillosa is placed within the Acaulospora longula / morrowiae / mellea ‘complex’, clearly separated from these species with support values> 95% in all analyses applied (data not shown). In the BLASTn analysis, the environmental LSU and ITS rDNA sequence with a closest match (97%) to A. papillosa was recovered from roots of maize ( KF 849639) in an agricultural experiment in Guangzhou, China ( Zeng et al. 2014).

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 1–9. Acaulospora papillosa. 1–2. Crushed spores formerly formed laterally on the neck of sporiferous saccules, and having three spore walls (outer, middle and inner wall; OW, MW, IW). Outermost wall layer (OWL1) hyaline and rapidly degrading; OWL2 pigmented and structural. 3–4. Papillae structure on the outer spore surface formed on evanescent OWL1. 5. Papillae structure partly disappearing in lactic acid based mountants. Cicatrix at the spore base without papillae. 6–9. Spore wall structure: OW triple-layered (OWL1-3), middle wall bi-layered (MWL1–2), IW with two visible layers (IWL1–2); IWL2 staining purple to dark purple in Melzer’s reagent.