Ornamentation types of conidia and conidiogenous structures in fasciculate Penicillium species using scanning electron microscopy

As part of a multidisciplinary approach to the taxonomy of the fasciculate Penicillium species, the conidial ornamentation of 320 strains was examined in order to determine the types and range of ornamentation and assess the stability of this feature as a taxonomic character. Five conidial ornamentation classes were identified: echinulate, tuberculate, reticulate, microtuberculate and microverrucate. The technique of cryoscanning was used for examining the penicillus, and assessing such characters as roughening, shape and orientation of the branches. The method provides a fast means of examining freshly frozen material in the absence of artefacts associated with air-drying, freezing and critical-point drying techniques. Studies on large numbers of conidia from the same isolate and from isolates referred to the same species showed the scanning electron microscopy results to be reproducible and provide an objective and accurate method for comparing micromorphological features. The ornamentation types can be of particular value in species identification.