Abstract
Growth and movement of Ralstonia solanacearum harboring the phage-modified plasmid were monitored in tomato seedlings. The plasmid contains a gene for green fluorescent protein (GFP) and is stably maintained in R. solanacearum cells without selection pressure. Bacteria harboring the plasmid can be tracked in planta by visualizing GFP fluorescence. For real-time monitoring of bacteria in planta, tomato seedlings were grown on agar medium and bacterial suspension was applied to the root apex. The bacterial invasion process was monitored by fluorescent microscopy. In susceptible tomato cultivars, strong GFP fluorescence was observed in hypocotyls and lateral roots as well as the taproot. In resistant cultivars, however, GFP fluorescence was rarely observed on lateral roots. Our results show that this monitoring system can be used to assess bacterial pathogenicity. GFP labeled filamentous phage (φRSS1) was infected for labeling R. solanacearum cells. Labeled cells by using phage showed similar behaviors in tomato plant. Interestingly, infection of R. solanacearum cells containing φRSS1 caused formation of organs similar to a lateral root.
