Characterization and pathogenicity of Septoria gaurina associated with leaf blotch disease on Gaura parviflora in China.
Gaura parviflora, a flowering plant of the family Onagraceae, is regarded as an invasive plant in China, but is subject to leaf blotch disease. Based on morphological features, we identified the causal agent to be Septoria gaurina. However, the phylogenetic position of S. gaurina remains unknown. Multilocus phylogenetic analysis using the internal transcribed spacer (ITS), β-tubulin (Tub2), actin (Act), calmodulin (Cal), translation elongation factor 1-α (EF), and 28S nrDNA (LSU) nucleotide sequences indicated that the isolates belonged to the Septoria genus. Pathogenicity tests demonstrated that the isolates produced symptoms on the leaves of G. parviflora. These symptoms included small, water-soaked, circular lesions formed on leaves inoculated with conidial droplets, and bigger, water-soaked lesions on leaves inoculated by conidial spraying. To our knowledge, this is the first report of S. gaurina as the causative agent of leaf blotch disease of G. parviflora in China.