Gigaspora rosea

WHOLE SPORES

COLOR: Hyaline to pale cream with a pale pink spot near the subtending hypha 

SHAPE: Globose to subglobose. 

SIZE DISTRIBUTION: 170–305 µm, mean = 246 µm (n = 70). 

SUBCELLULAR STRUCTURE OF SPORES

SPORE WALL: Formed by three layers (C1, C2, and C3). C1 and C2 are adherent and of equal thickness in juvenile spores, with the laminated layer thickening as the spore wall differentiates. Layer C3 differentiates prior to spore germination (Bentivenga & Morton 1995).

C1: A rigid, permanent outermost layer, smooth, 1.0–2.0 µm thick (average 1.5 µm). This layer is firmly adhered to C2 but tends to separate from it in some spores when pressure is applied to the slide.

C2: A layer composed of sublayers (lamellae), pale cream in color (0/20/80/0); 5–21 µm thick (average 10 µm). The lamellae are semi-plastic, resulting in variation in thickness within the same spore. In some spores, the sublayers can be individually distinguished. C2 reacts with Melzer’s reagent, turning dark reddish-brown (20-80-100-0) to very dark (40/80/100/10); the reaction to Melzer appears to be uneven, with some areas reacting more than others, forming darker circular spots in some spores. 

C3: A very thin germinative layer, showing many folds and tightly adhered to C2, 0.5–1.0 µm thick. Many papillae are formed in this layer before spore germination, typically concentrated near the region where the sporogenous cell is attached. This layer has the same coloration as C2.

SUBTENDING HYPHA 

WIDTH OF SPOROGENOUS CELL: 26–50 µm (mean= 40 µm).

SPOROGENOUS CELL WALL: Possibly consists of two layers (C1 and C2), which are continuous with layers 1 and 2 of the spore wall. However, only C2 is easily discernible under the microscope.

C2: Pale cream in color and therefore concolorous with the C2 of the spore wall; 0.5–2 µm thick (average = 1.0 µm) in the most distal part of the sporogenous cell.

SEPTUM: The suspensor hypha that gives rise to the sporogenous cell is septate. Septa were observed in the suspensor hypha approximately 45 µm from the base of the spore.

OCCLUSION: Plug-like closure, concolorous with the C2 layer of the spore wall.

Comparison with Original Description 

Color:

Description: White to cream with a pink spot near the subtending hypha

PNB103A: Hyaline to pale cream with a pale pink spot near the subtending hypha

Shape:

Description: Globose to subglobose

PNB103A: Globose to subglobose

Size:

Description: 230–305 µm

PNB103A: 170–305 µm, mean= 246 µm

Spore Wall – C1:

Description: Smooth outermost layer

PNB103A: Thin, smooth, 1.0–2 µm (mean = 1.5 µm)

Spore Wall – C2:

Description: Wall composed of two to five inseparable layers, 1–2 µm and 2.4–7.5 µm thick

PNB103A: Variable thickness, 5–21 µm (mean = 10 µm)

Spore Wall – C3:

Description: Not reported

PNB103A: Thin, with many folds, 0.5–1.0 µm

Suspensor Cell:

Description: A suspensor cell attached to the spore, generally spherical, 28–40 µm in diameter, occasionally subglobose

PNB103A: Cream-yellow bulbous cell, 26–50 µm in diameter (mean = 40 µm)

Taxonomic History

Manuscript: Nicolson, T.H. and N.C. Schenck (1979). Endogonaceous mycorrhizal endophytes in Florida. Mycologia 71(1): 178–198. 

Etymology: Latin (rosea = pink), referring to the pink spot associated with the spores in this species. 

Type: Spores originating from the soybean rhizosphere in Escambia County, Florida, in September 1972, maintained on Pensacola sp. in a greenhouse (holotype at OSC, and paratypes at FH and FLAS). 

Biogeography

Gigaspora rosea is a pandemic species, detected on all continents except Antarctica, present in 18 countries, and occurring in tropical, subtropical, temperate, and boreal regions. Gigaspora rosea has been recorded in various biomes such as Tropical and Subtropical Grasslands (Soteras et al. 2014), Deserts and Xeric Shrublands (Mahdhi et al. 2019), Temperate Broadleaf and Mixed Forests (Bever et al. 1996), Tropical and Subtropical Moist Broadleaf Forests (Vasconcellos et al. 2016), Mangroves (Ramírez-Viga et al. 2020), Temperate Conifer Forests (Koske et al. 1987), as well as in agroecosystems (Fernandes et al. 2016).

In Brazil, this species has been detected in agroecosystems, riverine dunes, riparian forests, upland (terra-firme) forests, and deciduous forests. Gigaspora rosea occurs in 7 states across the North, South, Northeast, and Southeast regions.

The map below shows the countries (in red) where Gigaspora rosea has been detected.

References:

Bever, J.D.; J. B. Morton; J. Antonovics and P.A. Schultz.  1996.  Host-dependent sporulation and species diversity of arbuscular mycorrhizal fungi in a mown grassland.  J. of Ecology 84:71-82. 

Fernandes RA, Ferreira DA, Saggin-Junior OJ, Stürmer SL, Paulino HB, Siqueira JO, Carneiro MAC. 2016. Occurrence and species richness of mycorrhizal fungi in soil under different land use. Can. J. Soil Sci. 96:271-280. 

Koske, R.E. (1987). Distribution of VA mycorrhizal fungi along a latitudinal temperature gradient. Mycologia, 79:55-68. 

Mahdhi M, Tounekti T, Abada E, Al-Faifi Z, Khemira H. 2019. Diversity of arbuscular mycorrhizal fungi associated with acacia trees in southwestern Saudi Arabia. Journal of Basic Microbiology DOI: 10.1002/jobm.201900471.
 

Ramírez-Viga TK, Guadarrama P, Castillo-Argüero S, Estrada-Medina H, García-Sánchez R, Hernández-Cuevas L, Sánchez-Gallén I, Ramos-Zapata J. 2020. Relationships between arbuscular mycorrhizal association and edaphic variables in mangroves of the Coast of Yucatán, Mexico. Wetlands 40:539-549. 

Soteras F, Grilli G, Cofré MN, Marro N, Becerra A. 2014. Arbuscular mycorrhizal fungal composition in high montane forests with different disturbance histories in central Argentina. Applied Soil Ecology 85:30-37. 

Vasconcellos RLF, Bonfim JA, Baretta D, Cardoso EJBN. 2016. Arbuscular mycorrhizal fungi and glomalin-related soil protein as potential indicators of soil quality in a recuperation gradient of the Atlantic Forest in Brazil. Land Degradation & Development 27:325-334. 

Images