Alternaria brassicicola
Courtesy of Dr. Christopher Lawrence, Virginia Bioinformatics Institute, Virginia Tech

Habitat

The genus Alternaria is comprised of many common saprophytic (derive nutrients from dead and/or decaying organic matter) and plant pathogenic species. Alternaria spores can be typically found in the air, soil, decaying plant material, wood, and foods. Alternaria brassicicola (Schweinitz, Wiltshire) is a ubiquitous plant pathogenic fungus but also exists as a saprophyte.

Biology

Alternaria brassicicola causes black spot disease (also called dark leaf spot) on virtually every important cultivated Brassica species including broccoli, cabbage, canola, and mustard. It is of worldwide economic importance resulting occasionally in 20-50% yield reductions in crops such as canola, mustard or rape. Like other diseases caused by Alternaria species, black spot appears on the leaves as necrotic lesions, which are often described as black and sooty with chlorotic yellow halos surrounding the lesion sites. Alternaria brassicicola, however, is not limited to infection of leaves, and can infect all parts of the plant including pods, seeds, and stems, and is of particular importance as a post-harvest disease. Alternaria brassicicola is considered a necrotrophic (causing death) plant pathogenic fungus and like other Alternaria species has been shown to secrete numerous toxic secondary metabolites and proteins that cause cell death via induction of apoptosis in plants or by directly damaging cells. Alternaria brassicicola has routinely been used as a model necrotrophic fungal pathogen in studies with Arabidopsis thaliana, also a weedy member of the Brassicaceae plant family. From a human health perspective, Alternaria brassicicola is representative of a genus of fungi that is considered one of the most potent sources of mold-derived allergens. Moreover, sensitization to Alternaria is also strongly associated with chronic respiratory diseases such as asthma and chronic rhinosinusitis.

See also http://genome.wustl.edu/genome.cgi?GENOME=Alternaria%20brassicicola