Morphology of softening and translucency in the stems of tomato and eggplant seedlings due to infection by Ralstonia pseudosolanacearum F1C1

Ralstonia pseudosolanacearum F1C1 is a soil-borne phytopathogenic bacterium with a broad host range that infects several economically important crops. This study primarily focuses on the infection of this phytopathogen in two such important crop seedlings: tomato and eggplant. The observations of the study reveal a complex set of symptoms that include drooping and blackening of the seedling stem, as well as blackening, chlorosis, and curling of cotyledon leaves. Notably, the symptom of stem softening and translucency is seen primarily in the water-submerged stem regions of both root- and leaf-inoculated seedlings. While the wild-type R. pseudosolanacearum F1C1 strain and its weakly virulent mutant phcA::{Omega} exhibited this phenotype in both tomato and eggplant seedlings, the virulence-deficient hrpB::{Omega} mutant did so only in a few eggplant seedlings but not in tomato seedlings. By investigating these unique pathological phenotypes in the infected seedlings, this study uncovers a unique symptom previously not reported in seedling inoculation experiments. The work also touches upon the distinct escape mechanisms exhibited by seedlings, revealing how some of its host plants might resist wilting despite infection, offering new avenues for future research. These findings contribute to the understanding of R. pseudosolanacearum pathogenesis, shedding light on its virulence and host response mechanisms.