The bacterium Pasteuria penetrans is an obligate parasite of root-knot nematodes and produces spores that persist in soil for many years. At present, in vitro cultivation is not feasible, thereby requiring inoculum production in vivo cultivation, inside nematode parasitizing potted plants. In this work, the differences in the development of P. penetrans in Meloidogyne spp. parasitizing roots of tomato (Lycopersicon esculentum), gherkin (Cucumis anguria) and "camapu" (Physalis angulata) were evaluated by histopathology of infected roots. Possible reasons for the differences found were analyzed, such as change in the giant cells or nematode females. The gherkin was the worst host for inoculum production and presented abnormal giant cells. The anatomy of giant cells and the bacterium development were similar in tomato and "camapu" root systems, but the P. penetrans life cicle was slightly shorter in tomato than in camapu.
