POPULATION GENETIC-STRUCTURE OF PHYTOPHTHORA-INFESTANS IN ECUADOR

The population genetic structure of Phytophthora infestans in Ecuador was assessed from 101 isolates collected from 1990 to 1992 and 111 iso lates collected in 1993. All isolates were analyzed for mating type an d allozyme genotype. Both samples were dominated (>95%) by a clonal li neage (EC-1) defined from neutral markers: 90/100 genotype for glucose -6-phosphate isomerase, 96/100 genotype for peptidase, Al mating type, and a previously unreported nuclear DNA fingerprint. The remaining is olates belonged to the US-1 clonal lineage, which has a worldwide dist ribution. Isolates in the 1993 sample were analyzed for virulence and metalaxyl sensitivity. All representatives of EC-I bad complex pathoty pes, with three pathotypes representing >60% of the collection. There was variation for metalaxyl sensitivity. There was no evidence for geo graphical substructuring on the basis of neutral markers, but there wa s evidence for limited substructuring based on metalaxyl sensitivity a nd specific virulence. We hypothesize that EC-1 has been recently intr oduced to Ecuador.