First Report of a Leaf Spot Disease on Watermelon Caused by Bipolaris spicifera in Egypt

In February 2017, watermelon plants showing light brown to blackish leaf spots were observed during a survey conducted in different growing areas in Minia governorate, Egypt (Fig. 1). A fungus was consistently isolated from leaf lesions on potato dextrose agar (PDA) incubated at 25°C for 7 days. Identification of isolated fungus was verified at Assiut University Mycological Center based on its morphological characteristics. Microscopic observations revealed that conidia measured 26 to 32 × 11 to 12 μm (average 28.5 × 11.5 μm) (Fig. 2). The fungus obtained from these samples was identified as Bipolaris spicifera Bainier and its telemorphic state Cochliobolus spicifer Nelson. Reproduction of symptoms on inoculated healthy watermelon leaves by the isolated fungus fulfilled Koch’s postulates and confirmed its pathogenicity. According to the available literature, this is the first report of leaf spot disease caused by Bipolaris spicifera Bainier on watermelon in Egypt.