An Innovative Approach to Study Ralstonia solanacearum Pathogenicity in 6 to 7 Days Old Tomato Seedlings by Root Dip Inoculation.

Ralstonia solanacearum (F1C1) is a Gram-negative plant pathogenic bacterium that causes lethal wilt disease in a wide range of plant species. This pathogen is very well known for its unpredictable behavior during infection and wilting its host. Because of its mysterious infection behavior, virulence and pathogenicity standardization are still a big challenge in the case of R. solanacearum. Here, we report an innovative pathogenicity assay of R. solanacearum (F1C1) in the early stage of tomato seedlings by root dip inoculation. In this assay, we employed 6-7days old tomato seedlings for infection grown under nutrients free and gnotobiotic condition. After that, pathogenicity assay was performed by maintaining the inoculated seedlings in 1.5 or 2 ml sterile microfuge tubes. During infection, wilting symptom starts appearing from ~48 h post inoculation and the pathogenicity assay gets completed within seven days of post inoculation. This method is rapid, consistent as well as less resource dependent in terms of labor, space and cost to screen large numbers of plants. Hence, this newly developed assay is an easy and useful approach to study pathogen virulence functions and its interaction with the host plant during wilting and disease progression at the seedling stage.