Disease Note.

Potato Early Blight Caused by Alternaria alternata in Brazil. L. S. Boiteux, CNPH/EMBRAPA CP 0218, 70359-970 Brasilia (DF), Brazil. F. J. B. Reifschneider, CNPH/EMBRAPA CP 0218, 70359-970 Brasilia (DF), Brazil. Plant Dis. 78:101. Accepted for publication 25 February 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0101D.

Although Alternaria solani Sorauer is the main causal agent of early blight in Brazil, Alternaria alternata (Fr.:Fr.) Keissl. was consistently isolated from potato (Solanum tuberosum L. 'Eba') leaves showing typical early blight symptoms in the Brasilia area of Brazil. Koch's postulates were completed under greenhouse conditions (22-28 C) by spraying leaves of potato cultivars Achat, Bintje, Apua, and Aracy at 45 days after emergence with a spore suspension adjusted to 105 conidia per milliliter. A susceptible reaction (characterized by large, circular, dark brown lesions, often with concentric rings) appeared 7-10 days later only in Achat and Bintje. Apua and Aracy, previously reported as resistant to A. solani(1), were not infected by A. alternata. This is the first report of A. alternata associated with early blight in Brazil.