First Report of Bacterial Spot Disease Caused by Pseudomonas capsici on Castor Bean in Korea

In August 2021, water-soaking symptoms of bacterial spot disease were observed on castor bean in a field in Gangseo District, Busan. Bacteria isolated from the lesion when cultured on tryptic soy agar appeared to be nonmucoid and pale green. To confirm whether the isolates were the causative agent of the spot disease, they were inoculated onto healthy castor bean plants. The same symptoms were observed on the inoculated tissue, and the bacteria were reisolated from the lesion. Furthermore, the isolates were consistent with the biochemical and physiological features of Pseudomonas capsici. Sequencing analysis using 16S rRNA and housekeeping genes (gyrB, rpoD) showed that the isolates shared a high sequence similarity with P. capsici. These results confirmed that the strains belonged to P. capsici. To our knowledge, this is the first report of bacterial spot disease caused by P. capsici on castor bean in Korea.