Abstract
Phosphite is a major weapon in management of Phytophthora diseases of trees. Application of phosphite makes plants resistant to infection. However, we know very little about the mechanism by which phosphite makes plants resistant. This is due largely to the lack of a simple inexpensive method for measuring phosphite in plant tissues. We have been developing new approaches to measuring phosphite in plant tissues. We arc also investigating how phosphite makes plants resistant to infection. For this we are using the plant Arabidopsis thaliana. The advantage of using this plant species is that mutants in the known defence pathways are available. This will allow us to pinpoint which pathways are involved in mediating resistance in phosphite treated plants.