Neothyriopsis Crous, gen. nov.
MycoBank number: MB 832028; Index Fungorum number: IF 832028; Facesoffungi number: FoF 12340;
Etymology: Name reﬂects its similarity to the genus Thyriopsis.
Ascostromata scutellate to conical, suborbicular, irregularly tuberculate, subcuticular, black, producing coralloid, hyaline haustoria in the epidermal cells, guard cells, cells surrounding the stomatal cavity and the ﬁrst layer of mesophyll; uni- to multilocular, opening by irregular apical ﬁssures exposing the ascospores; upper wall stromatic, composed of several layers of dark brown ﬂattened, thick-walled cells; basal wall well developed, composed of two layers of cells, the outer layer composed of pale brown, relatively thin-walled cells, which extend laterally for some distance beyond the base of the upper wall as an intracuticular, unicellular layer of radially elongated, hyaline cells, and an inner layer. Asci parallel on the basal wall between hyaline, deliquescent pseudoparaphyses, broadly clavate, wall thickened, especially at the apex, bitunicate, deliquescing before spore maturation. Ascospores hyaline when immature, becoming dark brown, thick-walled, subglobose to globose, ﬁnely verrucose, medianly 1-septate (adapted from Marasas 1966).
Type species: Neothyriopsis sphaerospora (Marasas) Crous
Notes: This pathogen is known to occur in Australia, Brazil, Chile and South Africa (Park et al. 2000). All attempts to cultivate it have proven unsuccessful, as ascospores germinate (on MEA, PDA), but die shortly thereafter.
As biotrophic pathogen, Neothyriopsis sphaerospora is distinct from the genus Thyriopsis, which occurs on needles of Pinus spp. Thyriopsis has thyrothecia that open by linear ﬁssures, sometimes Y-shaped, asci are bitunicate, 8-spored, and contain ascospores that are ellipsoidal, 1-septate, with cells of roughly equal size, rounded at the ends, highly constricted at the septa, hyaline to yellowish brown (von Arx & Müller 1975), which clearly distinguish it from N. sphaerospora. The ascostromata of Neothyriopsis are more similar to those of Thyriopsis, having upper walls composed of several layers of stromatic cells, and a basal wall of two cell layers. In addition to the difference in ascospores, Neothyriopsis also has well developed haustoria, which are absent in Thyriopsis.