suborder Gigasporineae

Gigasporineae
Morton & Benny (1990)

Arbuscules stain darkly in trypan blue or other stains (e.g., chlorazol black E, acid fuschin). Each arbuscule arises from a wide trunk (generally 4-6 µm) branching from an intraradical hypha through the cortical cell wall. Numerous second-order finely tipped branches of transitory duration are produced. With arbuscule senescence (degradation of fine tips), the trunk may remain intact in cells and appear as tightly packed coils. Duration of these coils is unknown. However, persistence of the total arbuscular network in mycorrhizal roots of pot cultures is longer for species of this suborder than those of Glomineae.

Auxiliary cells are thin-walled and fragile, forming singly or in clusters on branches from extraradical hyphae in soil, hyaline to dark brown in color. They form very early in mycorrhizal development (even forming on spore germ tubes) and often are most abundant around roots in pot cultures before the onset of sporulation. As sporulation increases, auxiliary cells generally decline in abundance in a pot culture environment.

Asexual spores formed singly from a morphologically specialized bulbous sporogenous cell formed terminally on a fertile hypha in soil; generally larger than 200 µm in diameter at maturity; ranging from white to dark red-black in color.

Intraradical hyphae are of variable widths because of considerable plasticity in shape (straight or with knobs, projections, or swollen regions). Colonization patterns consist of extensive coiling in all parts of a mycorrhiza, rather than mostly near entry points as is observed in species of Glomineae.

Extraradical hyphae generally of two morphotypes readily distinguished in pot cultures: coarse wide hyphae, 3-8 µm in diameter, and fine hyphae, 1-2 µm in diameter. Both are abundant during auxiliary formation, whereas the latter is less evident in 4-5 month-old cultures.

Fungi in this suborder are not "vesicular-arbuscular fungi" or "VAM fungi" because they do not form vesicles. Auxiliary cells, like vesicles, store energy-rich lipids, but they are extraradical rather than intraradical and their peak production occurs before rather than after (or during) sporulation. They also do not appear to be infective, and appear to serve as transitory storage structures of carbon.

Consists of only one family: Gigasporaceae

Arbuscules stain darkly in trypan blue or other stains (e.g., chlorazol black E, acid fuschin). Each arbuscule arises from a wide trunk (generally 4-6 µm) branching from an intraradical hypha through the cortical cell wall. Numerous second-order finely tipped branches of transitory duration are produced. With arbuscule senescence (degradation of fine tips), the trunk may remain intact in cells and appear as tightly packed coils. Duration of these coils is unknown. However, persistence of the total arbuscular network in mycorrhizal roots of pot cultures is longer for species of this suborder than those of Glomineae.
Auxiliary cells are thin-walled and fragile, forming singly or in clusters on branches from extraradical hyphae in soil, hyaline to dark brown in color. They form very early in mycorrhizal development (even forming on spore germ tubes) and often are most abundant around roots in pot cultures before the onset of sporulation. As sporulation increases, auxiliary cells generally decline in abundance in a pot culture environment.
Asexual spores formed singly from a morphologically specialized bulbous sporogenous cell formed terminally on a fertile hypha in soil; generally larger than 200 µm in diameter at maturity; ranging from white to dark red-black in color.
Intraradical hyphae are of variable widths because of considerable plasticity in shape (straight or with knobs, projections, or swollen regions). Colonization patterns consist of extensive coiling in all parts of a mycorrhiza, rather than mostly near entry points as is observed in species of Glomineae.
Extraradical hyphae generally of two morphotypes readily distinguished in pot cultures: coarse wide hyphae, 3-8 µm in diameter, and fine hyphae, 1-2 µm in diameter. Both are abundant during auxiliary formation, whereas the latter is less evident in 4-5 month-old cultures.