Occurrence of the Phytophthora Blight Caused by Phytophthora sansomeana in Atractylodes macrocephala Koidz.

Background: In September 2017, wilting and rhizome rot symptoms were observed on Atracty- lodes macrocephala Koidz. in Jecheon-si and Eumseong-gun. This study was carried out to isolate hitherto unidentified pathogenic fungi from A. macrocephala and to test the pathogenicity of isolated fungi against Atractylodes spp. genus such as A. macrocephala , A. japonica, and their interspecific hybrids. Methods and Results: The diseased plants were washed with running tap water, and the boundary between the healthy area and the diseased area was cut while the pathogens were isolated by grow-ing cultures from the diseased areas on Phytophthora semi-selective medium. The internal transcribed spacer (ITS) region of the isolates was used in this study for identification. Test plants were cultivated in the glasshouse at 20 ℃ - 30 ℃ for 4 months and then used for pathogenicity test. The pots with plants inoculated with mycelial plugs and zoospores were placed at 25 ℃ for 48 h in a dew chamber where relative humidity was above 95%, and then moved into the glasshouse at 20 ℃ - 30 ℃ . The presence or absence of pathogenicity of the strains was determined by evaluating the symptom of plant wilting. The inoculation test was performed in three replicates with a non-treated control. Conclusions: On the basis of results of ITS sequence analysis, the strains isolated from the diseased plants was identified as Phytophthora sansomeana . Biological assay using test plants con-firmed the pathogenicity of P. sansomeana against Atractylodes macrocephala. This is the first report of rhizome rot in A. macrocephala caused by P. sansomeana .