RAPD-PCR for Identification of Zoophthora radicans Isolates in Biological Control of the Potato Leafhopper

Abstract

Biological control studies require the ability to distinguish released pathogens from locally occurring isolates of the same species. We have developed a technique that differentiates genotypes using random amplified polymorphic DNA (RAPD) for the apomictic species Zoophthora radicans (Zygomycota: Entomophthorales), a pathagen of the potato leafhopper, Empoasca fabae (Homoptera: Cicadellidae). RAPD analysis was performed on Z. radicans isolates released in test plots in 1990 and 1991 for leafhopper control; isolates later recovered from the same plots and diverse other isolates were included in the analysis. RAPD fragment profiles of five recovered isolates proved very similar to those of the released isolates and different from all other isolates tested; they are probable descendants of the released isolates. One of the recovered isolates had RAPD profiles similar to isolates derived from aphids and probably represents a population endemic at the release site. In addition to verifying the successful establishment of our experimental releases, RAPD analysis revealed clear relationships among isolates derived from the same host taxon. We propose that this simple and relatively inexpensive method will be valuable in determining the establishment and spread of organisms released in biological control studies.