Alternaria alternata

Alternaria alternata has been recorded causing leaf spot and other diseases on over 380 host species. It is opportunistic pathogen on numerous hosts causing leaf spots, rots and blights on many plant parts. It also causes upper respiratory tract infections in AIDS patients and asthma in people with sensitivity.






  • Pale brown to olive brown
  • 25-60 x 3-3.5 µm
  • Straight or flexuous
  • Individual conidiophores arise directly from substrate forming bushy heads consisting of 4-8 large catenate conidia chains
  • Secondary conidiophores are generally short and 1-celled


  • Pale brown to light brown
  • Obclavate to obpyriform orellipsoid, short conical beak at the tip, or beakless
  • Surface smooth to verruculose
  • Size
    • 20-63 x 9-18 µm in size
    • (on PCA) mature conidia typically 10-30 x 5-12 µm
  • Septa
    • Several vertical and -8 transverse septa
    • (on PCA) 3-7 transepta, 1-5 longisepta
  • Chains
    • Produced in an often branched, long chain more than 5 conidia.
    • (on PCA) individual chains of 5-15 conidia, complex of branching chains may contain up to 50-60 conidia

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