Glomus eburneum and G. luteum, Two New Species of Arbuscular Mycorrhizal Fungi, with Emendation of G. spurcum

Abstract

Two species of arbuscular mycorrhizal fun- gi, Glomus eburneum and G. luteum, are described and the description of G. spurcum is emended. All species produce spores singly in soil. Glomus ebur- neum spores are hyaline or white to cream, usually irregular (40 X 60 to 140 X 160 jim diam) and more rarely globose (40-140 ,um diam). The spore wall consists of two adherent permanent hyaline layers, neither of which reacts in Melzer's reagent. The out- er layer is thin (<1.2 ,lm), and the inner layer is finely laminate. Spores of G. luteum are globose to subglobose, 60-180 jLm diam and pale yellow to dark yellow with a brownish tint. The spore wall consists of four layers, the two outer layers often degrading at maturity. The outer layer is mucilaginous and stains pinkish-red in Melzer's reagent. The second layer is hyaline and semirigid. Rigid, pale yellow to brownish yellow laminae comprise the third layer. Mature spores exhibit a fourth layer that is thin, flex- ible and may separate from the laminate layer under pressure. Both species were identified from pot cul- tures established with soil and root fragments from a semiarid giant sacaton (Sporobolus wrightii) grassland and subsequently cultured on sudangrass, Sorghum sudanense. Both species formed arbuscular mycorrhi-