Main page <> Text key to Group I <> Text key to Group II <> Text key to Group III <> Text key to Group IV <> Text key to Group V
Picture key for Group I <> Picture key for Group II <> Picture key for Group III <> Picture key for Group IV <> Picture key for Group V

KEYS TO SOME COMMON GENERA OF MOULDS

GROUP I

1. Spores 1-celled 2

1. Spores with more than one cell 12

Usually this is obvious. Occasionally spores may have darkened areas resembling septa, but these will not be visible in optical section when you focus on the centre of the spore.







2. (1) Colonies, spores, and other tissues colourless or brightly coloured 3


2. Colonies, spores, and/or other tissues dark coloured 8

The dark colour is either brown or black. The best indication of dark colours comes from looking at the culture itself, either directly or with a dissecting microscope. Under the compound microscope many brown structures will appear nearly colourless.






3. (2) Spores produced in chains 4

Often chains of spores break apart thoroughly when placed in a water mount. In many species of Aspergillus and Penicillium a few spores will remain together in a group, so that you can assume that they were originally in chains. On the other hand, species of Cladosporium produce chains of spores that completely disassociate on contact and leave no clue about their original orientation. The easiest way to check this is to examine the colony under the 10X objective of a compound microscope, being careful not to get spores on the lens.

3. Spores not produced in chains 6





4. (3) Conidiophores with a swollen head or vesicle bearing bottle-shaped phialides

Aspergillus


4. Conidiophores not swollen at apex 5







5. (4) Spores in unbranched chains, borne from clusters of cylindrical to bottle-shaped phialides; colonies usually green

Penicillium

Compare with Paecilomyces (Group II), Gliocladium (Group III), Scopulariopsis (Group III). and Talaromyces (Group IV)


5. Spores borne in branching chains from undifferentiated conidiophores; colonies often very fast growing and pink

Chrysonilia





6. (3) Spores borne in a sporangium with a columella; often with only the columella evident as a swollen hyphal tip; hyphae not septate

Mucor

Compare Rhizopus (Group I), Mortierella (Group II), Absidia, Circinella (Group V), and Zygorhynchus


6. Spores produced externally; hyphae septate 7






7. (6) Conidiophores well-developed and usually with a central axis; very fast growing and with conidiophores usually produced in small cushions of hyphae; often green

Trichoderma

Compare with Verticillium (Group II) and Gliocladium (Group III)


7. Conidiophores poorly developed or lacking; phialides produced singly along the vegetative hyphae; hyphae often aggregated into "ropes"; seldom or never green

Acremonium

Compare with Verticillium (Group II), Sporothrix (Group IV), and Phialophora (Group IV)






8. (2) Spores in chains, produced externally 9


8. Spores not in chains, produced inside sporangia or fruiting bodies (pycnidia) 10







9. (8) Conidiophores with a swollen head or vesicle bearing bottle-shaped phialides; conidial chains unbranched

Aspergillus


9. Conidiophores lacking a swollen apex; spore chains often branched; spores often both 1- and 2-celled

Cladosporium






10. (8) Spores produced inside a fruiting body (pycnidium) with a cellular wall; hyphae septate

Phoma

Compare Pyrenochaeta (Group IV) and Microsphaeropsis (Group IV) and also be sure that asci are not present at a very early stage


10.Spores produced within a sporangium with a columella, often with only the columella evident as a swollen hyphal tip; hyphae not septate 11





11. (10) Sporangiophores with rhizoids (branched "roots") at base

Rhizopus

Compare with Absidia (figure 2B)


11. Sporangiophores lacking rhizoids

Mucor

Compare with Mortierella (Group II), Absidia (figure 2B), Circinella (Group V), and Zygorhynchus (figure 2C)






12. (1) Spores with transverse septa only 13


12. Spores with both transverse and vertical septa 14








13. (12) Spores dark, produced in branched chains

Cladosporium


13. Spores colourless or brightly coloured, mostly with more than two cells, often canoe-shaped, usually produced in slimy masses; colonies often pink

Fusarium

Compare Cylindrocarpon (not treated here), Candelabrella, Monacrosporium (both Group III), and Trichophyton (Group V)





14. (12) Spores usually in chains, usually club-shaped; colonies grey to brown

Alternaria

Compare Ulocladium and Stemphylium (Group II)


14. Spores in clusters but not in chains, usually spherical; colonies often (but not always) bright orange or yellow and purplish in reverse

Epicoccum

Compare with Stemphylium (Group II)

Main page <> Text key to Group I <> Text key to Group II <> Text key to Group III <> Text key to Group IV <> Text key to Group V
Picture key for Group I <> Picture key for Group II <> Picture key for Group III <> Picture key for Group IV <> Picture key for Group V