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Grafting experiments were carried out in order to understand tomato resistance mechanisms to Pseudomonas solanacearum. Resistant scions grafted on susceptible root‐stocks wilted, indicating that vascular tissues of resistant cultivars were not tolerant to higher bacterial populations than susceptible ones. Colonization frequencies and bacterial densities observed in plant grafted on resistant or susceptiblle root‐stocks showed that resistance was correlated to the limitation of bacterial spread in the lower part of the stem.

The colonization of eggplant, pepper and tomato by Pseudomonas solanacearum was compared. Latent infections were observed in pepper and eggplant, indicating that this phenomenon was general in the main hosts of P. solanacearum. In eggplant and pepper, as in tomato, resistance did not arise from a resistance to root colonization by the bacteria. In tomato and eggplant, resistance mechanisms appeared to be similar: spread of P. solanacearum was limited in resistant cultivars. In contrast, in pepper this limitation was not observed and plants appeared more tolerant to high bacterial populations than tomato and eggplant.