Background

Bacterial wilt pathogen Ralstonia solanacearum dwells in soil. When favorable condition comes, the bacterium enters inside the suitable host plant through root, grows, colonizes there and ultimately kills the plant. R. solanacearum strain (F1C1) had been isolated and characterized from a wilted chilli plant nearby Tezpur (Assam), north-east India (Kumar et al., 2013). Owing to the lethality and its exceptional wide host range, R. solanacearum considered as the second most devastating bacterial phytopathogen around the world (Mansfield et al., 2012). In spite of that, no effective approach so far is available to deal with this pathogen and its associated disease.

Regarding its virulence and pathogenicity assay, several existing methods are commonly in use such as soil drenching, leaf clip, petiole cut as well as stem inoculation but, in the other hand it is also reported that these methods are not found to be very much appropriate in analyzing minute virulence and pathogenicity differences in few mutants strain of R. solanacearum (Macho et al., 2010). In the wake of developing a potent pathogenicity assay, we have developed and standardized an innovative root inoculation method to study R. solanacearum pathogenicity in tomato seedling (Singh et al., 2018). Along with the pathogenicity assay (Figure 1), this approach is also equally helpful in bacterial bio-control development and plant protection assay against this wilt pathogen at the seedling stage. Recently many other research groups also have employed seedling stages of tomato plants for studying R. solanacearum pathogenicity in number of occasions (Pradhanang et al., 2000; Artal et al., 2012; Kumar, 2014; Kumar et al., 2017). This vascular pathogen is well known for its mysterious infection behavior and wide range of host adaptability, therefore R. solanacearum is also referred as a suitable model to investigate fundamental aspects of plant-pathogen interaction and host adaptations (Genin and Boucher, 2002; Genin, 2010; CollandValls, 2013; Singh et al., 2018).