Alternaria petasitis sp. nov., causing Alternaria leaf spot of Japanese butterbur in Japan

Abstract

We isolated anAlternaria species from brown leaf spots of Japanese butterbur in Kanuma city, Tochigi Prefecture in August 1996, and in Akagi village, Gunma Prefecture in June 1997. The isolated fungus formed irregularly shaped colonies with yellow-brown pigment on potato sucrose agar (PSA) and potato dextrose agar (PDA). When Japanese butterbur leaf was inoculated with small fragments of mycelia, brown spot lesions were produced. Conidial suspensions of the fungus also produced similar spots on Japanese butterbur leaf. Under moist conditions, a small amount of conidia was produced on the spots. The conidia were somewhat variable in shape and size, measuring 102–362×9–22 μm for the Kanuma isolate and 70–392×11–27 μm for the Akagi isolate. Length of the conidial beak was also variable, being 30–280 μm for the Kanuma isolate and 30–302 μm for the Akagi isolate. The fungus could not be identified with any ofAlternaria species hitherto known, suggesting that it was new to science. We proposed to designate the fungus asAlternaria petasitis, giving a Latin description of the new species.