Identification of Soybean Leaf Spot Pathogen Epicoccum sorghinum in Beijing

Soybean leaf spot disease occurs with a wide range in Beijing, having a serious impact on soybean production. In order to analyze the causes of soybean leaf spot disease in Beijing, thus providing a theoretical basis for the efficient prevention and control of the disease, in this study, we analyzed the symptoms of the disease in the field, collected the diseased plants and isolated the pathogenic bacteria by tissue separation method, and purified the pathogenic bacteria by single spore separation method on the surface of the agar plate. Then we test the pathogenicity according to Koch postulates and determined the type of pathogenic bacteria by morphology and molecular biology. The results showed, at first the pathogenic bacterial colonies were white or gray-white at the initial stage, and all the pathogenic bacterial colonies were reddish-brown at the later stage. The center of the colonies was orange-red, pink, or white with bulges, and the edges were gray-white in an irregular shape. The conidia was spherical, nearly spherical or oval, with a septum in the middle, mostly in clusters, about 20 μm × 5 μm. Combined with molecular biology result, the pathogen was identified as Epicoccum sorghinum. The E. sorghinum was isolated from soybean for the first time, and it was found that the pathogen was highly pathogenic after re-inoculation.