USE OF CELLULOSE-ACETATE ELECTROPHORESIS FOR RAPID IDENTIFICATION OF ALLOZYME GENOTYPES OF PHYTOPHTHORA-INFESTANS

Cellulose-acetate electrophoresis (CAE) provided excellent resolution of allozyme genotypes of Phytophthora infestans at the two loci Glucos e-6-phosphate isomerase (Gpi) and Peptidase (Pep). The cellulose-aceta te system has many advantages over traditional starch gel analyses. It is much faster, running in only 15 to 20 min compared to 16 to 18 h f or starch gels, and because of the short run times the gels do not nee d to be cooled during electrophoresis. Cellulose acetate is purchased as precast plates, which eliminates the time required to pour starch g els. Both Gpi and Pep can be analyzed using a single buffer in the CAE system, whereas four buffers are required to resolve these enzymes us ing starch gels. Finally, only very small amounts of tissue (e.g., 3,0 00 sporangia washed from lesions or infected tuber slices) are require d for CAE, so it can be useful even when the fungus has not been isola ted into axenic culture. These advantages may allow CAE to be useful a s a diagnostic tool in field situations, where rapid determination of genotypes could aid disease management strategies. Because populations of P. infestans in the United States and Canada currently are highly clonal, mating type and response to metalaxyl are highly correlated wi th allozyme genotype. Therefore, CAE of allozyme genotypes could provi de a rapid, accurate method for predicting mating types and metalaxyl sensitivities of P. infestans within fields.