Development of the sensitive lateral flow immunoassay with silver enhancement for the detection of Ralstonia solanacearum in potato tubers.

Ralstonia solanacearum is a dangerous and economically important pathogen of potatoes and other agricultural crops. Therefore, rapid and sensitive methods for its routine diagnostics are necessary. The aim of this study was to develop a rapid control method for R. solanacearum with a low limit of detection (LOD) based on a lateral flow immunoassay (LFIA) with silver enhancement. To minimize the LOD, the membrane type, antibody amount for conjugation with gold nanoparticles, conjugate concentration and antibody concentration in the analytical zone were optimized. Silver enhancement was used to decrease the LOD of the LFIA. For silver enhancement, release fiberglass membranes with pre-absorbed silver lactate and hydroquinone were placed on the analytical zone, and a drop of silver lactate was added. The LFIA with silver enhancement was found to be 10-fold more sensitive (LOD 2×10(2) CFU/mL; 20 min) in comparison with the common analysis (LOD 2×10(3) CFU/mL; 10 min). The specificity of the developed LFIA was studied using different strains of R. solanacearum (54 samples) and other widespread bacterial pathogens (18 samples). The LFIA detected all tested strains, whereas non-specific reactions were not observed. The developed tests were used for the control of bacteria in extracts of infected and non-infected potato tubers, and the quantitative analysis results (based on the densitometry of line colouration) were confirmed by ELISA with a correlation coefficient equal to 0.965.