Nematospora sinecauda sp. nov., a yeast pathogen of mustard seeds

Abstract

An undescribed yeast species was recovered from oriental (Brassica juncea) and yellow (B. hirta) mustard seeds. The new species most closely resembled Nematospora coryli but its asci were rarely cylindrical. The asci and ascospores of N. sinecauda were smaller and the spores did not possess a whip-like appendage. During germination a sprout cell formed first on the smooth anterior surface of the spore above the median ridge. The posterior region of the spore was decorated with interrupted concentric ridges. A description of the new species is given.

1 Saccharomycotina and Taphrinomycotina: The Yeasts and Yeastlike Fungi of the Ascomycota

“…Symptoms are generally disfigurement and disruption of the infected plant tissue. E. sinecaudum was discovered by Holley et al (1984) to cause seed infection in oriental and yellow mustard in Saskatchewan, Canada. The remaining known species of Eremothecium, E. cymbalariae, appears uncommon but has been isolated as a pathogen of flax and other plants (Arnaud 1913).…”

Fungal Morphogenesis

“…Although the hyphal form is used by many plant pathogens to invade the host, filamentous growth itself may not be adequate, or even required, for pathogenesis. For example, Holleya sinecauda, the dimorphic pathogen of mustard seeds, is isolated almost exclusively in the yeast form in plant lesions (Holley et al 1984). Mutations that enable U. maydis to grow solely in a filamentous form do not support Ustilago pathogenicity (Barrett et al 1993).…”

Holleya gen. nov., an ascosporogenous yeast genus for the Q9-equipped organism whose ascospores are needle-shaped with smooth surfaces in their anterior half and concentric ridges in their posterior half and without appendage.

“…In contrast, N. coryli possesses needle-shaped or spindle-shaped smooth ascospores with a whiplike appendage (4). The arrangement of spore bundles in N. sinecauda asci is somewhat different from that in N. coryli asci (5). The ascospores of Metschnikowia reukaufii Pitt et Miller (1968), a related organism are of similar size and shape and without appendage, however, N. sinecauda is dissimilar with respect to many characters including the number of ascospores per ascus, the arrangement of spore bundles, the vegetative cell shape, and other features (5,10).…”

“…However, the Co-Q system of N. sinecauda was similar to those of Metschnikowia species (Q-9) (8). According to HoLLEY et al (5), N. sinecauda produces needle-shaped or spindle-shaped ascospores with a smooth anterior surface, a posterior region girded by concentric ridges, and no appendage. The ascospore size is about three times smaller than that of N. coryli.…”