A Rapid Pathogenicity Assay of R. solanacearum in 10-12 Days Old Eggplant (Solanum melongena) Seedlings by Root Inoculation Approach

Abstract

1.This study has reported standardization of pathogenicity assay of Ralstonia solancearum in eggplant seedlings by root inoculation approach. Though the approach is similar to my earlier published work that done with tomato seedlings, in case of eggplant, duration of the seed germination, age of the seedlings, symptom timing and progression rate of the disease are different. In an introductory observation, R. solanacearum F1C1 inoculation was performed in to 10-12 days old eggplant seedlings resulted in lethal infection in eggplant seedlings and subsequently most of these infected seedlings got wilted within 10 days of post-inoculation. Colonization studies of R. solanacearum in wilted as well as infected eggplant seedlings were confirmed by GUS staining as well as fluorescence microscopy. In addition, we also observed that wrapping of the eggplant seedlings root by a thin layer of cotton soon after the pathogen inoculation in the root, enhanced the disease progression and wilting of the inoculated seedlings. The standardized root inoculation protocol in eggplant seedlings was found to be efficient to distinguish mutant strains of different virulence genes such as hrpB, phcA and pilT from wild-type R. solanacearum. Due to its reproducibility and consistency in different eggplant cultivars, the standardized protocol described here is practically observed as an useful and rapid approach to investigate R. solanacearum pathogenicity and disease progression at the early seedling stage of eggplant.