To determine whether this difference in the kinetics of cell death could be attributed to the protective capacity of the strains, the same types of experiment were conducted using mutants of biocontrol strains affected in their protective capacity. Whatever the strains and the plants considered, the percentage of dead cells increased more rapidly in the presence of the biocontrol strains than in the presence of their mutants affected in their protective capacity (Fig. 4). These results, which must be confirmed with a broader array of strains, allow one to distinguish a protective from a nonprotective strain of F. oxysporum, and lead to a fundamental question: is the cell death induced by different strains of F. oxysporum of the same nature? As we proposed the hypothesis that the protection induced by Fo47 could be compared to the HR induced by biotrophic fungi, and knowing that HR induces programmed cell death, it would be interesting to characterize the type of death induced by Fo47 and to compare it to the cell death induced by the pathogen in the host plant.
Figure 4.