Search on : Taxa descriptions


 Add this item to the list   Penicillium verrucosum Dierckx
Page number:32 
Remarks (internal):The name Penicillium verrucosum was introduced by Dierckx (1901) with a very short description. Biourge (1923) redescribed the species based on a new isolate and the original drawings and notes left by Dierckx (G. L. Hennebert, pers. commun.). Raper and Thom (1949) considered Dierckx's species as a synonym of P. viridicatum Westling (1911) and stated that P. verrucosum has been commonly interpreted as representing a member of the P. viridicatum series. Biourge's strain (CBS 603.74) agrees with Raper and Thom's concept of P. viridicatum.
P. verrucosum is the oldest name of a whole series of epithets published for a complex of fasciculate Penicillia with rough-walled conidiophores and globose to subglobose, smooth to slightly rough-walled conidia. Strains now accomodated in P. verrucosum were disposed by Raper and Thom (1949) into the P. viridicatum, P. ochraceum, P. cyclopium-series and partly the P. expansum and P. granulatum-series. Also the species of the P. terrestre-series (subsection Funiculosa) and some of the P. commune-series (subsection Lanata) are included in P. verrucosum.
P. verrucosum is somewhat similar to P. roqueforti Thom. Both species are characterized by roughened, two-stage branched conidiophores. However P. roqueforti can easily be distinguished from P. verrucosum by the broadly spreading, very thin, strictly velvety colonies. Moreover, the short conidiophores of P. roqueforti are more coarsely roughened though occasionally the granulations of the walls may be lacking. Besides the branched conidiophores P. roqueforti also produces simple conidiogenous structures which are often smooth-walled. The globose, smooth conidia are usually larger, reaching a diameter of 3.5-6.0 µm. In older cultures sclerotium-like structures are sometimes produced.
Though the species placed in synonymy with P. verrucosum agree in the structures of their conidiophores, they may differ in the colour of the colonies. Moreover, there is some variation in the rate of growth, fasciculation and roughness of the conidiophores. Based primarily on the differences of colony colour, P. verrucosum can be separated into 6 varieties, album, corymbiferum, cyclopium, ochraceum, melanochlorum and verrucosum. Separation into these varieties seems to be reasonably practicable. Variety identification is occasionally difficult due to the existence of intergrading strains.
Description type:Non-original description 
Description:Penicillium verrucosum Dierckx
Penicillium verrucosum Dierckx - Annls Soc. scient. Brux. 25: SS. 1901. Numerous synonyms cited below under the varieties.
Colonies on Czapek agar growing restrictedly or spreading broadly, usually consisting of a dense felt of single conidiophores mixed with small tufts of fasciculate conidiophores, mostly produced in the marginal areas, giving the colony surface a granular appearance, in other strains the colony surface is predominantly velvety or almost floccose; degenerated strains may be floccose to lanose. Colour yellow-green, dark-green, grey-green or blue-green, rarely white or ochraceous. Vegetative aerial mycelium mostly absent, sometimes yellowish or produced as a white central cushion. Reverse usually uncoloured, sometimes yellowish, in other strains with pink, orange or brown shades. Odour pronounced, usually earthy and pungent, sometimes also aromatic or somewhat fruity. Conidiophores t00-400 X 3.0-4.0 µm, two-stage branched, sometimes three-stage branched, rough-walled (in some strains of var. cyclopium nearly smooth-walled), [p. 33] branches and metulae appressed. Phialides flask-shaped, 7.0-9.0 X 2.0-2.5 µm, with short but distinct necks. Conidia globose t0 subglobose, sometimes ellipsoidal when young, smooth-walled or nearly so, greenish, 3.0-4.0 µm in diameter.
Colonies on malt agar with similar growth, but usually thinner and less fasciculate. Odour usually more pronounced than on Czapek agar. Conidiophores as on Czapek agar, but mostly more markedly rough-walled.
Taxon name: