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First Report of Cercospora traversiana on Trigonella coerulea in Bulgaria

In the spring of 1996, diseased plants of Trigonella coerulea were noted in an experimental area at Kazanlak, Bulgaria. The primary symptoms were leaf spots 8 to 2 mm in diameter, light brown then becoming gray and slightly zonate, and surrounded by a diffuse chlorotic margin. When single lesions occur the disease normally develops as a typical leaf spot. However, the development of more than one spot is followed rapidly by yellowing and withering of entire leaflets. Stem lesions usually begin at the point of leaf attachment, extend both directions about 15 to 20 mm, and often encircle the stems. Isolations on potato dextrose agar (PDA) yielded a slow-growing, gray fungus. Conidia from the isolated fungus when inoculated at 3.10⁴ spores per ml on potted T. coerulea seedlings and kept in a moisture chamber for 48 h caused foliar spots in 5 to 8 days and sporulating structures similar to those seen in field observations. Simultaneous inoculation of T. foenum-graecum (fenugreek) plants produced similar symptoms, but the percentage of successfully inoculated leaves (3.6%) was lower than in T. coerulea (27.6%). Conidiophores of the fungus are dark, arising in clusters, unbranched, septate (1 to 3), and have small conidial scars. Conidia are hyaline, straight, multicelled (1 to 17), tapering at the base, and measured 30 to 212 × 4 to 6 μm. The pathogen was identified as Cercospora traversiana Sacc. and this is the first report of its occurrence in Bulgaria.