Molecular approaches to the taxonomy of Phytophthora capsici and P.citrophthora using isozyme and mitochondrial DNA analyses

Molecular approaches to systematics, such as use of isozyme electrophoresis and analysis of restriction fragment length polymorphisms (RFLPs) of mitochondrial DNA (mtDNA), provide an objective, genetic approach to testing current taxonomic schemes for the genus Phytophthora. Using these techniques we have examined isolates of two species: P.capsici and P.citrophthora. Our findings indicate that P.citrophthora exists as two distinct subgroups, one from citrus and kiwi from worldwide sources (CTR1) and another from cocoa in Brazil (CTR2). Isolates of P.capsici form three subgroups. A large subgroup CAPI contained isolates from Capsicum sp., tomato cucurbits, Piper nigrum and cocoa; a second subgroup CAP2 contained isolates from Piper nigrum, macadamia, cocoa and rubber from tropical locations. Finally, a third subgroup CAP3 consisted only of isolates attacking cocoa in Brazil