GENETIC-VARIATION IN AN INTRODUCED APHID PEST (METOPOLOPHIUM-DIRHODUM) IN NEW-ZEALAND AND RELATION TO INDIVIDUALS FROM EUROPE

RAPD-PCR was used to determine the genetic variation of Metopolophium dirhodum collected in a winter wheat field and in a nearby 2.5-m-high suction trap at Lincoln, New Zealand. Over three collection dates, fiv e distinct genotypes were identified, using two primers (OPK16 and OPC 09) independently. There was a significant temporal effect on the rati o of genotypes in populations collected in the field. There was no sig nificant spatial aggregation or association of these genotypes in the field. Two of the genotypes present in the field were also detected in the suction trap sample. Using a higher resolution method of RAPD-PCR (with the Stoffel fragment of Tag polymerase), a total of 124 genotyp es were distinguished from 142 individuals collected from Scotland and New Zealand. The Jaccard similarity index (S) was used to measure sim ilarity between individual aphids within and between populations from both hemispheres. All populations were very diverse (S < 0.33). Howeve r, at similar crop growth stages, M. dirhodum was significantly more d iverse in Scotland than in New Zealand. The results are discussed in r elation to the value of monitoring aphid flights for pest forecasting, and in terms of the most appropriate RAPD-PCR techniques.