ARS | Publication request: Cladosporium herbarum is a cause of a leaf spot disease on Caltha leptosepala (marsh-marigold) in western North America

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 14, 2008
Publication Date: November 21, 2008
Citation: Johnson, D.A., Pimentel, G., Dugan, F.M. 2008. Cladosporium herbarum causes a leaf spot on Caltha leptosepala (marshmarigold) in western North America. Online Plant Health Progress doi:10.1094/PHP-2008-1121-01-RS.

Interpretive Summary: The fungus Cladosporium herbarum is a cosmopolitan and extremely common saprophyte, occasionally causing disease in ripe fruits or on plants that are senescent. There are very few reports of host specialization for this fungus. In this instance, isolates of C. herbarum originating from Caltha leptosepala (marsh marigold) were pathogenic on that species under experimental conditions, but Cladosporium herbarum isolates from other plant species were not pathogenic, nor were other, common species of Cladosporium. This particular species of marsh marigold (there are several species in the genus Caltha) is a common indicator plant in alpine and subalpine environments of the Pacific Northwest.

Technical Abstract: Caltha leptosepala ssp. howellii and Caltha leptosepala ssp. leptosepala (marsh-marigold, Ranunculaceae) inhabit stream banks and wet meadows in subalpine zones in the northern Rocky and Cascade mountain ranges of North America. Cladosporium herbarum (anamorphic Davidiellaceae) is a cosmopolitan saprophytic fungus and epiphyte invading senescing tissues of many plants, inducing disease in ripe fruits, and occupying other diverse environments. Instances of biotypes of C. herbarum potentially specialized to cause disease on a given host are rare. We here report an instance of a biotype causing disease on Caltha leptosepala. We propose the name Cladosporium leaf spot for this disease.