Determination of Genomovar Status of Burkholderia cepacia Causing Banana Finger-tip Rot and Development of a Simple Semi-selective Medium for Isolation of the Pathogen

Abstract

Banana finger-tip rot disease was observed in commercial fields in Pingtung County, Taiwan. Symptoms included small and externally distorted shape of diseased fingers, and brown discoloration of pulps. The pathogen was isolated and identified as Burkholderia cepacia in a previous study. The genomovar status of banana finger-tip rot pathogen in B. cepacia complex was further determined by PCR-RFLP pattern analysis of 16S rDNA and recA. The results suggested that the banana finger-tip rot pathogen was closely related to B. cepacia genomovar Ⅲ. In addition, the recA nucleotide sequence-based phylogenetic tree showed that banana finger-tip rot pathogen aligned more closely with the recA group Ⅲ A of genomovar Ⅲ. For epidemiological studies, a simple semi-selective medium (QY-TP) was developed for the isolation of banana finger-tip rot pathogen from diseased and symptomless banana fingers. All B. cepacia strains tested grew well on QY-TP medium, but other plant pathogenic bacteria such as Erwinia carotovora, E. chrysanthemi, Ralstonia solanacearum, and Xathomonas spp. failed to grow on the medium. The medium allowed recovery of 92 to 98% of the B. cepacia colonies grown on Luria-Bertani agar medium, and inhibited growth of most background bacteria. Use of QY-TP medium made it possible to determine the infestation rate of banana fingers in the field.