Isolation and identification of Burkholderia gladioli on Cymbidium orchids in Korea

Bacterial diseases of Cymbidium orchids continue to threaten the floriculture industry. Bacterial isolates were isolated and cultured from Cymbidium plants exhibiting disease symptoms: black lesions with or without water-soaking on leaves. To identify the bacterial isolates, we performed polymerase chain reaction (PCR) amplification using species-specific primers. The pathogen was tentatively identified as Burkholderia gladioli, which was first described as a phytopathogen, and later associated with human infections, especially with patients with cystic fibrosis. PCR-restriction fragment length polymorphism analysis of 16S ribosomal DNA (rDNA) products digested with HinfI and sequencing of the 16S rDNA confirmed the isolate as B. gladioli. Burkholderia gladioli strains infecting plants are divided into two pathovars: alliicola and gladioli. Pathogenicity tests showed that the isolate proved to be pathogenic to Cymbidium orchid but not to onion plants, a common host for B. gladioli pv. alliicola. To the best of our knowledge, this is the first report of B. gladioli in Cymbidium orchids in Korea.