NPDN 2007 Meeting - Diagnostic features of Corynespora cassiicola and its associated diseases.

NPDN National Meeting 2007

Poster Abstract

Diagnostic features of Corynespora cassiicola and its associated diseases.

Authors: Linley J. Smith (1), ROBERT L. SCHLUB (2)

Affiliations: (1) University of Florida, Gainesville, Florida; (2) University of Guam Cooperative Extenion Service, Mangilao, Guam, USA

Identifying C. cassiicola as a causal agent is complicated by variability of symptoms, inconsistencies in the fungus’s sporulation and morphology, and ability to grow competitively as a saprophyte. It is primarily a foliar pathogen; however, it will spread to stems and fruits as in the case of papaya and tomato. On most hosts, lesions are discrete small spots less than 10 mm in diameter; however, marginal non-discrete lesions do occur. Field samples often do not reveal conidiophores or spores until incubated in a moisture chamber for 24 to 48 hours. Longer incubation periods often give rise to saprophytic isolates. To avoid misidentification with other fungal pathogens such as species of Cercospora and Helminthosporium key diagnostic features should be noted. Corynespora spores germinate from terminal cells, whereas Cercospora spores germinate from every cell. Additional diagnostic features include pseudo-septation, sporulation in chains, and percurrent proliferation of conidiophores. Its widespread occurrence during a 2003-2006 survey of various Pacific Islands and Florida corroborates recent literature indicating that C. cassiicola is increasing in importance as a pathogen on cucumber, papaya, soybean, and tomato. We believe that misdiagnosis has resulted in an underestimation of economic losses associated with this fungus.

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