N. C. Schenck

Incidence of mycorrhizal fungi on six field crops in monoculture on a newly cleared woodland site.

The yearly incidence of root colonization and extramatrical spores of vesicular-arbuscular (-VA) mycorrhizal fungi were determined for six agronomic crops grown in monoculture for 7 yr on a newly c...

Endogonaceous Mycorrhizal Endophytes in Florida

In Florida 21 species of Endogonaceae forming vesicular-arbuscular mycorrhizae are reported. Eight species of the genus Glomus, including a new species G. clarus, and three species of Sclerocystis ...

Temperature response of Endogone mycorrhiza on soybean roots.

SUMMARYGrowth of an Endogone sp. on soybean roots was evaluated in autoclaved soil maintained at temperatures ranging from 17 to 41 C. Maximum arbuscular development of Endogone in the root (mean o...

Spore Germination and Germ Tube Growth of a Vesicular-Arbuscular Mycorrhizal Fungus in Vitro

The effects of mineral nutrients, thiamine, pH, and organic substrates on germination and germ tube growth of a vesicular-arbuscular mycorrhizal fungus were examined. Surfacesterilized azygospores of Gigaspora margarita were plated on 1% water agar containing different components and incubated at 28 C up to 30 da. Maximum germination and germ tube growth occurred when 20 mg 1-1 CaH2PO4 was used, whereas 24 mg 1-~ NH4NO3 did not affect germination and depressed germ tube growth by 55%. Potassium or concentrations of soluble nutrient salts as high as those used to grow seedlings axenically had no effect on spore germination or germ tube growth. Thiamine at 0.1 mg 1-1 increased germination, and maximum germ tube growth occurred at 0.01 mg 1-1. The interaction between medium pH and medium composition was significant. Spore germination was not enhanced by any of the organic substrates. Low concentrations (4 g 1-1) of sucrose favored germ tube growth. Relation of these results to nutrition and root-colonizing ability of VA mycorrhizal spores is discussed.

Several New and Unreported Vesicular-Arbuscular Mycorrhizal Fungi (Endogonaceae) from Colombia

Six new species of Endogonaceae are described, Acaulospora appendicula, A. longula, A. mellea, A. morrowae, Glomus manihotis, and Entrophospora colombiana. Acaulospora ap? pendicula is an unusual species that forms chlamydospores and thin-walled accessory cells similar to those formed by species in the genus Glomus. In addition, observations on the occurrence of Acaulospora foveata in Colombia and some characteristics of this fungus not included in the original description are presented. A dichotomous key to all described species of Acaulospora is presented.

Germination of Chlamydospores of Three Glomus Species as Affected by Soil Matric Potential and Fungal Contamination

Chlamydospores of Glomus darum, G. etunicatum, and G. macrocarpum were placed on filter membranes and buried in pasteurized or nonpasteurized soils having matric potentials of -10, -100, -1000, and...

Germination and hyphal growth of vam fungi during and after storage in soil at five matric potentials

Abstract Four vesicular-arbuscular mycorrhizal (VAM) fungi, Cigaspora margarita Decker & Hall, Glomtu mosseae (Nicol. & Gerd.) Gerdemann & Trappe, Glomus intraradices Schenck & Smith, and Acavlospora languid Spain & Schenck. were studied to characterize the variety of responses of VAM fungi to storage. Spores were stored at 23°C for up to 4 months in soil at several matric potentials [Ψ m], then removed and exposed for 1 month in soil at field capacity to induce germination. Each species studied has a different response to storage duration and moisture availability, reflecting the complexity of the problem of storage of VAM fungi in soil. Net germinability, the difference in percentage germination between that which occurred in storage and germination after the subsequent month at field capacity, was effectively zero for Gi. margarita. Hyphae continued to grow and additional germ tubes were produced upon removal from storage. Gi. margarita spores which produced one germ tube per spore during storage in moist soil subsequently produced less root colonization of Paspalum notation than spores stored in drier soil. Net germinability of spores of G. intraradices increased with decreasing storage Ψm and was independent of storage duration. Upon removal from storage, preexisting hyphae resumed growth. Net germinability of spores of G. mosseae was inversely proportional to duration of storage and independent of Ψ m. Spores which germinated in storage did not resume growth upon removal from storage. Net germinability of A. longula increased with duration of storage and was independent of moisture availability during storage, indicating a dormant period.

TWO NEW DIMORPHIC SPECIES IN THE ENDOGONACEAE: GLOMUS AMBISPORUM AND GLOMUS HETEROSPORUM

Two new vesicular-arbuscular (VA) mycorrhizal fungi (Endogonaceae) from Florida, Glomus ambisporum and G. heterosporum, differ from all previously described species in the production of two distinct spore types. Black sporocarps or sporocarp aggregates of Glomus ambisporum are produced in the soil and hyaline spores are formed within host tissues. The outer wall of sporocarpic spores is subhyaline with a faint reticulum of hexagonal plates. Glomus heterosporum has light to dark brown sporocarps or sporocarp aggregates produced externally to host tissues and forms hyaline spores within host tissues. The outer wall of the sporocarpic spores is hyaline, smooth, and evanescent. Sporocarps of both species have spores radially arranged around a central hyphal plexus which resemble sporocarps of Sclerocystis rubiformis. This is the first report of dimorphism in the genus Glomus.

A unique code for each species of VA mycorrhizal fungi

(1990). A Unique Code for Each Species of Va Mycorrhizal Fungi. Mycologia: Vol. 82, No. 2, pp. 256-260.