A Quick Method for Screening Biocontrol Efficacy of Bacterial Isolates Against Bacterial Wilt Pathogen Ralstonia solanacearum in Tomato

Ralstonia solanacearum is a bacterial phytopathogen able to cause bacterial wilt disease in more than 200 plant species. Plant disease biocontrol strategies are used for controlling this disease and tomato is used as a model plant to conduct R. solanacearum associated studies. Conventional screening methods such as seed bacterization, soil drenching and root bacterization (in grown plants) to assess the ability of biocontrol bacteria to antagonize R. solanacearum under in planta conditions in different hosts are time-consuming and costly. A fast, cost effective method is a key requirement to advance the research on R. solanacearum biocontrol. In this protocol, we have inoculated the roots of tomato seedlings with bacterial isolates showing antagonistic activity against R. solanacearum under in vitro conditions. After 16 h of treatment with the antagonizing bacteria, seedlings were inoculated with R. solanacearum by a well-established root-dip method. Then the seedlings were maintained at controlled conditions and the number of wilted/dead seedlings were recorded up to 10th day post R. solanacearum inoculation. Biocontrol efficacy was calculated from the records for each tested isolate. This protocol is advantageous than already available protocols in the sense that it can be completed within a very short duration (similar to 18 days for tomato) and there is no requirement of culture media to maintain the seedlings. This method can be used for quickly screening large number of bacterial isolates and different host genotypes within a short period of time and at a minimum cost.