Alternaria conidia

Alternaria is a common genus of asexual ascomycetes especially in outdoor environments; Alternaria conidia are often the second most common airborne fungal spore genus in temperate climates around the world. Members of this genus are common saprobes, leaf surface organisms, and plant pathogens. Alternaria species can grow on a number of indoor substrates, but they are not usually found at high levels indoors. Alternaria spores are highly allergenic.

Alternaria conidia are multicellular with transverse and longitudinal septa. The large, club-shaped and deeply pigmented spores are formed in chains, often with attachment scars on the tapered apical cell (beak) and the basal cell.