Ralstonia solanacearum is one of the most destructive plant bacterial pathogens worldwide. The population
dynamics and genetic stability are important issues, especially when an avirulent strain is used for
biocontrol. In this study, we developed a rapid method to differentiate the virulent and avirulent strains
of R. solanacearum and to predict the biocontrol efficiency of an avirulent strain using high performance
liquid chromatography (HPLC). Three chromatographic peaks P1, P2 and P3 were observed on the HPLC
spectra among 68 avirulent and 28 virulent R. solanacearum strains. Based on the HPLC peaks, 96 strains
total were assigned to three categories. For avirulent strains, the intense peak is P1, while for virulent
strains, P3 is the majority. Based on the HLPC spectra of R. solanacearum strains, a chromatography titer
index (CTI) was established as CTIi ¼ Si/(S1þS2þS3) 100% (i represents an individual HPLC peak; S1, S2
and S3 represent peak areas of P1, P2 and P3, respectively). The avirulent strains had high values of CTI1
ranging from 63.6 to 100.0%, while the virulent strains displayed high values of CTI3 ranging from 90.2 to
100.0%. Biological inoculation studies of 68 avirulent strains revealed that the biocontrol efficacy was the
best when CTI1 ¼ 100%. The purity and genetic stability of R. solanacearum strains were confirmed in the
P1 fraction of avirulent strain FJAT-1957 and P3 fraction of virulent strain FJAT-1925 after 30 generations
of consecutive subculture. These results confirmed that fractioning by HPLC and their deduced CTI can be
used for rapid and efficient evaluation and prediction of an isolate of R. solanacearum. To the best of our
knowledge, this is the first report that HPLC fractioning can be used for rapid differentiation of virulent
and avirulent strains of R. solanacearum.