Species and strain identification of the predatory mite Euseius finlandicus by RAPD-PCR and ITS sequences

The variation within and between Finnish Euseius finlandicus populations wa s investigated by RAPD-PCR and ITS sequence analyses. Resin DNA extraction was found to be a suitable method for samples of single mites used in PCR. The banding patterns from 24 RAPD primers and 10 primer pairs were very sim ilar and reproducible in all specimens of the predatory mite studied. Howev er, the E. finlandicus K-strain could be distinguished from organophosphate -resistant predatory mites (R-strain), since almost all of them produced a 1400 bp RAPD-PCR product, which was missing or very rare in other strains s tudied. Another RAPD band of ca. 680 bp was in turn much more common in oth er mites of E. finlandicus than in the K-strain mites. Mite specific primer s were designed and used to follow the survival of the R-strain released on apple trees. The 680 bp band obtained with specific primers was specific t o the species E. finlandicus mites studied, including those that had been n egative with RAPD primers. The 1400 bp specific primers could be used as a marker for following the survival of R-strain mites on apple trees. At the species level it was possible to distinguish adults and eggs of E. finlandi cus from Anthoseius rhenanus and Phytonemus pallidus by RAPD-PCR. In additi on, a band at 480 bp was found to correspond to DNA of the predatory mite P hytoseius macropilis, when both specific primer pairs were used together. I t was not possible to amplify the ITS region of E. finlandicus rDNA using s everal primer pairs that work in other mites and aphids. However, a basidio mycete rDNA sequence was amplified with one of these ITS primer pairs in K- strain mites. Finally, it was found that fungal rDNA-specific primers ampli fied an ITS region of ca. 650 bp in several strains of E. finlandicus. Inte rnal primers, designed to amplify the central part of the 650 bp product, s uccessfully amplified this product from all the mites.