Dominikia litorea Błaszk. & Kozłowska, 2018

Błaszkowski, Janusz, Ryszka, Przemysław & Kozłowska, Anna, 2018, Dominikia litorea, a new species in the Glomeromycotina, and biogeographic distribution of Dominikia, Phytotaxa 338 (3), pp. 241-254 : 246

Dominikia litorea Błaszk. & Kozłowska , sp. nov. Fig. 3A‒H

MycoBank MB 823832

Collections examined: Holotype:— ZT Myc 58910 ( Z + ZT), isotypes: 3602‒3614 ( DEPSE), and OSC 161511 , OSC 161512 ( OSC).

Etymology:— litorea , referring to the sandy dunes, in which the species exists.

Diagnosis:—Differs from D. indica in the phenotypic and histochemical properties of spore wall layers, the morphological characters of the spore subtending hypha, and in molecular phylogeny.

Description:—Spores formed in soil in loose to compact clusters of 3‒22 spores; develop blastically at the tip of hyphae branched from a parent hypha continuous with a mycorrhizal extraradical hypha (Fig. 3A‒H); clusters frequently with incorporated soil debris (Fig. 3D, E). Spores hyaline; globose to subglobose; (11‒)25(‒35) μm diam; rarely egg-shaped or irregular, 23‒33 × 29‒50 μm; with one subtending hypha (Fig. 3A‒H). Spore wall consists of two layers (layers 1 and 2) of equal thickness, (0.8‒)1.0(‒1.2) μm thick (Fig. 3B‒H). Layer 1, forming the spore surface, permanent, unit (not divided into visible sublayers), smooth. Layer 2 permanent, laminate, smooth, consisting of very thin, <0.5 μm, sublayers tightly adherent to each other and therefore difficult to see; this layer frequently separates from the lower surface of layer 1 in crushed spores and uncrushed spores subjected to the pressure of a microscope cover slip (Fig. 3B‒G). In Melzer’s reagent, only layer 2 usually stains pale red (7A3) to pastel red (7A5), rarely high red (9A8), or turns pastel yellow (3A4; Fig. 3C‒H). Subtending hypha hyaline; straight or recurved, usually funnel-shaped, more rarely cylindrical, rarely slightly constricted at the spore base; (2.5‒)3.7(‒9.0) μm wide at the spore base (Fig. 3C‒H). Wall of subtending hypha hyaline; (0.8‒)1.3(‒2.0) μm thick at the spore base; composed of two layers continuous with spore wall layers 1 and 2 (Fig. 3G, H). Pore (0.8‒)1.6(‒5.8) μm diam, open (Fig. 3F‒H). Germination unknown.

Mycorrhizal associations:—As indicated studies of trap cultures, in the field, D. litorea probably lived in mycorrhizal symbiosis with X. spinosum that had colonized sand dunes of the Mediterranean Sea located near Verico, Greece. However, spores of the fungus were not found in the field-collected rhizosphere soil of X. spinosa and no molecular analyses were performed to confirm the presence of D. litorea in roots of the plant species.

In single-species cultures with P. lanceolata as host plant, D. litorea formed mycorrhiza with arbuscules, vesicles, and intra- and extraradical hyphae. All the structures were widely distributed along the root fragments examined and stained clearly [violet white (16A2) to deep violet (16E8)] in 0.1% Trypan Blue.

Distribution and habitat:—Despite during the last 34 years J. Błaszkowski examined the occurrence of AMF in ca. 2500 field-collected soil samples and ca. 3000 trap cultures that represented different habitats, mainly maritime dunes, located in different regions of Africa, Asia, Europe, Brazil and USA, D. litorea was found only in one trap culture. The culture represented the Greece sand dunes of the Mediterranean Sea located near Verico. However, BLAST searches indicated that D. litorea has probably also been associated with roots of an unnamed plant species growing in China. The identity of the SSU‒ITS‒LSU sequences of D. litorea and two SSU‒ITS‒LSU sequences (KF836940, KF836961) of the Chinese AMF named Glomus sp. 6 , which were obtained in so called environmental studies, was 98%. Of the RPB1 gene sequences deposited in public databases, the percent identity of none suggested a molecular conspecificity with our new species. The highest identity was only 92% and regarded, among others, D. indica .