Specific and sensitive detection of Ralstonia solanacearum in soil with quantitative, real-time PCR assays

Aims:  The aim of this study was to develop a sensitive and an effective method suitable for large-scale detection and quantification of Ralstonia solanacearum in soil.
Methods and Results:  Based on the specific sequence of R. solanacearum strain G1000, the primer pair R.sol1-R.sol2 and the TaqMan probe Rs-pro were designed, and specific and sensitive PCR detection methods were successfully established. The detection limit was 100 fg μl⁻¹ DNA in conventional PCR and 1·2 fg μl⁻¹ in real-time PCR. By combining real-time PCR with the modified protocols to extract DNA from soil, it was possible to achieve real-time detection of R. solanacearum in soil, and the degree of sensitivity was 100 fg μl⁻¹. To detect inhibition in soil samples, an exogenous internal positive control (IPC) was included preventing false negative results, and IPC was successfully amplified from all samples tested. The methodology developed was used to detect the presence of R. solanacearum in tobacco fields in China.
Conclusions:  The real-time PCR combined with the protocol to extract DNA from soil led to the development of a specific, sensitive and rapid detection method for R. solanacearum in soil.
Significance and Impact of the Study:  The real-time PCR improves the detection sensitivity and specificity and provides an important tool for routine detection of R. solanacearum in soil samples and for epidemiological and ecological studies.