Case histories:
– ptCC
Appearance of colonies
CYA: 60-70 mm diameter, plane, sparse to moderately dense, velutinous in marginal areas at least, often floccose centrally, sometimes deeply so; mycelium only conspicuous in floccose areas, white; conidial heads usually borne uniformly over the whole colony, but sparse or absent in areas of floccose growth or sclerotial production, characteristically Greyish Green to Olive Yellow (1-2B-E5-7), but sometimes pure Yellow (2-3A7-8), becoming greenish in age; sclerotia produced by about 50% of isolates, at first white, becoming deep reddish brown, density varying from inconspicuous to dominating colony appearance and almost entirely suppressing conidial production; exudate sometimes produced, clear, or reddish brown near sclerotia; reverse uncoloured or brown to reddish brown beneath sclerotia
MEA: 50-70 mm diam, similar to those on CYA although usually less dense
G25N: 25-40 mm diam, similar to those on CYA or more deeply floccose and with little conidial production, reverse pale to orange or salmon
Appearance of conidia
Bright yellow-green (or less commonly yellow); rather variable in shape and size; relatively thin walls; smooth to moderately rough (the majority being finely rough)
Temperature and growth
– Rapid growth at both 25°C and 37°C
– At 37°C, colonies usually 55-65 mm diam, similar to those on CYA at 25°C, but more velutinous, with olive conidia, and sometimes with more abundant sclerotia
– No growth at 5°C
Sclerotia
Produced by some isolates, at first white, rapidly becoming hard and reddish brown to black, spherical, usually 400- 800 µm diam. Teleomorph not known. Conidiophores borne from subsurface or surface hyphae, stipes 400 µm to 1 mm or more long, colourless or pale brown, rough walled; vesicles spherical, 20-45 µm diam, fertile over three quarters of the surface, typically bearing both metulae and phialides, but in some isolates a proportion or even a majority of heads with phialides alone; metulae and phialides of similar size, 7-10 µm long; conidia spherical to subspheroidal, usually 3.5-5.0 µm diam, with relatively thin walls, finely roughened or, rarely, smooth.
Diseases
Usually A. fumitagus and A. flavus are the causes of Aspergillus keratitis.
Economic significance
Aspergillus flavus and Aspergillus parasiticus can produce aflatoxins are generally known as storage fungi, but they can also cause ear rots in the field. These species are observed as a gray-green, powdery molds and they can be detected in corn because they produce compounds that are fluorescent under black light.
