Genus/species: Alternaria alternate (Torula alternata, Alternaria tenuis, Macrosporium erumpens, Alternaria erumpens, Macrosporium meliloti, Macrosporium polytrichi, Macrosporium seguierii)
- Colony: Malt agar: Brownish Grey to black with white edges, producing a “suede-like” coating of spore stalks.
- WL: Will produce “masses of vegetative mycelium”. This type of growth is rarely seen in nature, and is not as useful for identification, since the conidia are more often used.
- Spore: Large, brown, multicelled, obclavate (larger at one end, sort of like a squeeze bulb), may be beaked, may be solitary or much more often in branching Longicatenatae (L. catenae, chains): chains of 10 or more spores (See photo)
- Liquid Growth: (ie dispersed, pellicle, film, clumpy)
Characteristic Secondary Metabolites: Altenuene – soluble in Acetone/1M NaOH, alternariol, alternariol monomethyl ether, altertoxin I, tentoxin and tenuazonic acid (Bottolico and Logrieco, 1998).
Ubiquitous, usually saprophytic but capable opportunistic parasite/pathogen. On grapes can appear as a black smut on the surface.
Conidia Morphology (see above description), Secondary metabolites (see above)
Role in wine:
Normal vineyard/winery flora. Likely present with other molds on wet/injured fruit. Can contribute to rot. Not amenable to growth under wine/fermentation conditions but can produce a moldy taint in wines made from infected clusters. A. alternatapresents more of a hazard to the health of employees, as it has been associated with asthma symptoms in US homes, and may cause skin legions.
A. Alternaria is not a concern in wine. Like other molds, it is quickly killed by SO2 and the fermentative process. Fungicide sprays are effective in the field.
- Picco, M. Anna and Rodolfi, Marinella. Assesments of Indoor Fungi in Selected Wineries of Oltrepo Pavase (Northern Italy) and Sottoceneri (Switzerland). Am. J. Enol. Vitic. 55:355-362 (2004).
- USDA Fungal Database (Online) http://nt.ars-grin.gov/fungaldatabases/new_allView.cfm?whichone=FungusHost&thisName=Alternaria%20alternata&organismtype=Fungus&fromAllCount=yes