The biological characteristics of the pathogenic agent of steviae leaf spot disease

Taxonomy identification suggests that the pathogenic agent of steviae leaf spot disease in Heilongjian province is Septoria steviae Ishiba Yokoyama et. Tani. It grew slowly. Its growth ratio and the yield of pycnidium and conidia differed greatly under 8 different culture media. The yield of conidia was affected significantly by illumination, but not the growth ratio of mycelium was. Reducing the glucose content of the PDA culture medium, its mycelium grew more slowly, but the yield of conidia in unit area could be promoted. Boron, as a microelement, could promote the yield of conidia in certain density. This fungus could live in pH 3-10 condition. But the optimal growth condition is pH 5.0-6.0.