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Background : During 2016 to 2017, Bacterial Rot symptom has been observed on Atractylodes macrocephala Koidz. in Yeongju-si, Mungyeong-si, Jecheon-si and Eumseong-gun. This experiment was carried out to identify pathogenic bacteria that has not been reported up to now from A. macrocephala and to test pathogenicity of isolated bacteria against A. macrocephala.
Methods and Results : Nine types of representative bacteria strains depending on colony size and color were isolated from surface disinfested symptomatic tissue that was macerated and streaked onto lysogeny broth (LB) medium with agar. Fungi were not recovered from any tissue that was surface disinfested and placed into acidified potato dextrose agar. Only one strain cause dark brown leaf rot symptom on A. macrocephala leaves soaked in bacterial suspensions. Potted A. macrocephala plants were used to test for pathogenicity. Inoculum was prepared by suspending the bacteria in sterile distilled water (SDW) for a final concentration of approximately 105 CFU/㎖. Suspensions were sprayed until runoff onto three replicate plants. Control plants were sprayed with SDW until runoff. Plants maintained in a dew chamber with 100% relative humidity at 30℃. After 3 days, leaf rot lesions developed on all inoculated plants; lesions later turned dark brown and appeared similar to symptoms observed in the field. Plants treated with water developed no symptoms. Same bacteria re-isolated onto LB from symptomatic tissues.
Conclusion : On the basis of 16S rRNA sequence analysis, the strain isolated from A. macrocephala was identified as Pseudomonas viridiflava. Biological assay method using Potted plants confirmed the pathogenicity of Pseudomonas viridiflava. This is the first report of bacterial rot caused by Pseudomonas viridiflava on A. macrocephala.
