Figure 7. Different defense-disease relations illustrated by a ‘see-saw but see-see’ model.

For Pectobacterium atrosepticum (A), the model describes the interaction according to the ‘see-saw principle’: increased defense is associated with decreased disease. For Phytophthora infestans (B), the model describes the interaction according to the ‘see-see principle’: increased defense is associated with increased disease. A plausible explanation for these differences is proposed by a general interaction model (Figure 8).