Molecular Differentiation of Two Strains of the Parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae) Using Specific PCR Primers

Two strains (Sav and Bam) of the parasitoid Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae) showed different sensitivity to organophosphate insecticides. By using polymerase chain reaction (PCR) and DNA sequencing, we demonstrated clear molecular difference between these two strains. DNA markers that are specific for the Bam strain were developed, and PCR-generated DNA fragments were cloned and sequenced. Two DNA fragments unique to the Bam strain contained 365 and 584 nucleotides. A pair of specific primers was designed from each fragment. PCR-amplification of the DNA from individual wasps generated fragments of the expected sizes only in the Bam strain. Studies conducted on F1 and F2 hybrids produced from crossing and backcrossing between resistant and susceptible strains indicated that these DNA markers are located on mitochondria and inherited exclusively maternally. Probes developed from these fragments may be used in assessing genetic information of natural populations and in studies on physiological or biochemical differences between the strains of this beneficial insect.