*rbarreto@ufv.br

Accepted for publication 21/10/05

Rudbeckia laciniata (common names: cutleaf coneflower in USA or margarida-amarela in Brazil) is a member of the Asteraceae and native to North America. It is traditionally used in the USA as a medicine, as well as being grown widely as an ornamental in the USA and abroad. During 2004 and 2005, R. laciniata plants cultivated at the Campus of the Universidade Federal de Viçosa (Minas Gerais, Brazil) were found attacked by a severe foliage disease. Primary leaf symptoms are circular-to-elliptical, dark brown-to-nearly-black leaf spots (eye–spots), 1.0-7.0 x 1.5-17.0 mm diameter and surrounded by a yellow halo. The spots coalesced, leading to extensive leaf necrosis with occasional shot-holes (Figs 1-2). Petiole and stem lesions are brown, elongated and irregularly dispersed.

Figure 1-2: Symptoms of Corynespora cassiicola on Rudbeckia laciniata. 1: General view of Rudbeckia laciniata with leaf spot symptoms; 2: Close-up of a leaf with typical eye-spot pattern of lesions

A dematiaceous hyphomycete with the following morphological features was consistently found associated with the lesions: conidiophores formed singly (150.0-262.5 µm long x 7.5-12.5 µm thick), 3-8 septate and brown; conidia fusiform, obclavate to subcylindrical, straight or curved (62.5-154.0 x 18.0-22.5 µm), subhyaline to brown, 5-16 distosseptate (Figs 3-8). The organism conformed most closely to Corynespora cassiicola, a highly polyphagous fungus (Ellis, 1971). A sample was deposited in the local herbarium (VIC 28791).

Figure 3-8: Corynespora cassiicola ex Rudbeckia laciniata. 3-4: Conidia; 5. Close-up of the conidial scar; 6-7: Conidiophores; 8: Tip of conidiophore showing the enteroblastic conidia formation. Scales bar: Figs. 3-4 = 50 µm; Figs. 5-8 = 20 µm	Figure 9: Eye-spot symptoms on Rudbeckia laciniata produced seven days after inoculation with a suspension of conidia of C. cassiicola

Pure cultures were cultivated from sporulating leaf lesions on V8 juice agar. Three unwounded healthy plants were brush-inoculated with a conidial suspension containing 4.4 x 105 conidia per ml and left for 24 hours in a humid chamber. Similar symptoms to those observed in the field were seen after 7 days on inoculated plants (Fig. 9). C. cassiicola was re-isolated from these lesions. Control plants showed no leaf spots. This is the first record of C. cassiicola attacking R. laciniata worldwide (Farr et al, 1989).

Ellis MB, 1971. Dematiaceous Hyphomycetes. Kew, UK: Commonwealth Mycological Institute.

Farr DF, Bills GF, Chamuris GP, Rossman AY, 1989. Fungi on Plants and Plant Products in the United States. St. Paul, USA: APS Press.

Lorenzi HL, Souza HM, 1995. Plantas Ornamentais no Brasil. Nova Odessa, Brazil: Editora Plantarum.

The British Society for Plant Pathology