ABSTRACT
Alternaria is a genus of asexual or imperfect fungi assigned with the class hyphomycetes. Fungi in this genus are anamorphs of ascomycetes, including members of the genus Pleospora. Alternaria is a dematiaceous mold, which includes, at present, about 50 species and varieties. However, only eight species have been implicated as human pathogens: A. alternata, A. brassicicola, A. chartarum, A. stemphylioides, A. dianthicola, A. infectoria, A. pluriseptata, and A. tenuissima. A. iridis is mentioned only as an allergic strain.1,2
In 1817 Nees described this telluric fungus is characterized by chains of spores with apical beak under the name of Alternaria tenuis. Subsequently Fries noted in 1832 described that Alternaria species are characterized by very distinctive large multicellular dictyospores that have a beak and are produced in chains. Species of Alternaria occur as parasites on a number of crop plants, causing early blight or leaf spot diseases, or as saprobes on a wide variety of organic substrates. This genus is prominent in aerobiological literature because it is recognized as an important aeroallergen as well as plant pathogen.3,4
Many pathogenic species of Alternaria have a worldwide distribution and are infective to a variety of plants including potato, tomato, onion, and members of Brassicacee.5 In general, Alternaria attacks plants under stress, especially
those affected by drought, insect infestation, or senescence. Alternaria spores are passively dispersed from infected leaves by moderate to strong gusty wind, with velocities of 2-3 m/s required for spore release. As a component of the dry air spora, dispersal typically occurs during dry weather that immediately follows periods of rain or heavy dew.
