The Suborder Glomineae

Glomineae
Morton & Benny (1990)

Arbuscules stain with a wide range of intensity, from almost invisible to darkly in trypan blue or other stains (e.g., chlorazol black E, acid fuschin). Each arbuscule arises from a hyphal branch 2-6 µm in width. Branching from the main trunk appears to become progressively thinner to finely tipped ends. The trunk hypha sometimes is swollen and coils, but not to the degree found in species of Gigasporineae. The arbuscular network often is hard to find in pot cultures older than 3-4 months or in older roots in the field. It is replaced by mostly a hyphal network with or without numerous vesicles and/or spores.

Vesicles are formed terminally (usually) on branch hyphae within or between cortical cells (usually the latter). In many species, vesicles are thin-walled and thus may vary considerably in size and shape. Rarely do they acquire any pigmentation, and thus require staining to be visible in roots (except under UV light, where they often autofluoresce). Their appearance in mycorrhizal development varies considerably with species, from immediately after entry into a root to late in colonization. Abundance of vesicles also varies with species, from absent or rare to the most abundant fungal form in a mycorrhiza. NOTE: Absence of vesicles is NOT taxonomically informative because it provides no information on genetic potential.

Asexual spores formed singly, in loose aggregates, in tight clusters with or without a binding peridium, or in highly organized sporocarps. In all forms, spores arise from a nonspecialized cylindrical to flared (or constricted) fertile hypha; either terminally, intercalarily, or laterally. They generally less than 200 µm in diameter at maturity, although some exceptions exist; white to dark red-black in color. Spores generally form in soil, but some species (mostly in Glomaceae), also may form abundant spores within roots.

Intraradical hyphae are of variable widths because of some plasticity in shape (straight or with swollen regions at entry points or where coiling occurs). Colonization patterns consist of coiling often present in localized regions of entry into roots, with numerous straight hyphae growing parallel with the root axis. Interconnecting branches often are at right angles to the parent hyphae to form "H" connections. Similar patterns may be seen in Gigasporineae, but to a much lesser extent.

Extraradical hyphae is highly variable in width and in thickness of the hyphal wall among species, but morphological types are poorly documented thus far.

Referred to generally as "vesicular-arbuscular mycorrhizal (VAM) fungi".

Four familes currently are recognized in this suborder:

Acaulosporaceae and Glomaceae are more derived taxa in the phylogeny of Glomales (see tree here)

Archaeosporaceae and Paraglomaceae are ancestral taxa (same tree above)

Arbuscules stain with a wide range of intensity, from almost invisible to darkly in trypan blue or other stains (e.g., chlorazol black E, acid fuschin). Each arbuscule arises from a hyphal branch 2-6 µm in width. Branching from the main trunk appears to become progressively thinner to finely tipped ends. The trunk hypha sometimes is swollen and coils, but not to the degree found in species of Gigasporineae. The arbuscular network often is hard to find in pot cultures older than 3-4 months or in older roots in the field. It is replaced by mostly a hyphal network with or without numerous vesicles and/or spores.
Vesicles are formed terminally (usually) on branch hyphae within or between cortical cells (usually the latter). In many species, vesicles are thin-walled and thus may vary considerably in size and shape. Rarely do they acquire any pigmentation, and thus require staining to be visible in roots (except under UV light, where they often autofluoresce). Their appearance in mycorrhizal development varies considerably with species, from immediately after entry into a root to late in colonization. Abundance of vesicles also varies with species, from absent or rare to the most abundant fungal form in a mycorrhiza. NOTE: Absence of vesicles is NOT taxonomically informative because it provides no information on genetic potential.
Asexual spores formed singly, in loose aggregates, in tight clusters with or without a binding peridium, or in highly organized sporocarps. In all forms, spores arise from a nonspecialized cylindrical to flared (or constricted) fertile hypha; either terminally, intercalarily, or laterally. They generally less than 200 µm in diameter at maturity, although some exceptions exist; white to dark red-black in color. Spores generally form in soil, but some species (mostly in Glomaceae), also may form abundant spores within roots.
Intraradical hyphae are of variable widths because of some plasticity in shape (straight or with swollen regions at entry points or where coiling occurs). Colonization patterns consist of coiling often present in localized regions of entry into roots, with numerous straight hyphae growing parallel with the root axis. Interconnecting branches often are at right angles to the parent hyphae to form "H" connections. Similar patterns may be seen in Gigasporineae, but to a much lesser extent.
Extraradical hyphae is highly variable in width and in thickness of the hyphal wall among species, but morphological types are poorly documented thus far.