Fungal resistance to plant antibiotics as a mechanism of pathogenesis

Many plants produce low-molecular-weight compounds which inhibit the growth of phytopathogenic fungi in vitro. These compounds may be preformed inhibi tors that are present constitutively in healthy plants (also known as phyto anticipins), or they may be synthesized in response to pathogen attack (phy toalexins). Successful pathogens must be able to circumvent or overcome the se and fungal defenses, and this review focuses on the significance of fung al resistance to plant antibiotics as a mechanism of pathogenesis. There is increasing evidence that resistance of fungal pathogens to plant antibioti cs can be important for pathogenicity, at least far some fungus-plant inter actions This evidence has emerged largely from studies of fungal degradativ e enzymes and also from experiments in which plants with altered levels of antifungal secondary metabolites were generated. Whereas the emphasis to da te has been on degradative mechanisms of resistance of phytopathogenic fung i to antifungal secondary metabolites, in the future we are likely to see a rapid expansion in our knowledge of alternative mechanisms of resistance. These may include membrane efflux systems of the kind associated with multi drug resistance and innate resistance due to insensitivity of the target si te. The manipulation of plant biosynthetic pathways to give altered antibio tic profiles will also be valuable in telling us more about the significanc e of antifungal secondary metabolites for plant defense and clearly has gre at potential for enhancing disease resistance for commercial purposes.