The resolution of Californian populations of Liriomyza huidobrensis and Liriomyza trifolii (Diptera : Agromyzidae) using PCR

Liriomyza trifolii (Burgess) and Liriomyza huidobrensis (Blanchard) are imp ortant vegetable pests in California. Populations of each species differ in their impact in central and southern regions. This difference may be expla ined by geographical or host plant differences in each of the regions. We u sed random amplified polymorphic DNA polymerase chain reactions to assess g enetic differences between two laboratory populations of each species colle cted from central and southern California. Individual L. trifolii from the two regions could be discriminated by the presence/absence of PCR products. No such qualitative differences were apparent in PCR products amplified fr om L. huidobrensis individuals, but the origins of individuals could be dif ferentiated using a bootstrap analysis of marker frequencies. Marker primer s were used to compare held and laboratory individuals. No evidence was fou nd for the existence of further populations or of hybrid populations in cen tral and southern California. The distribution of populations of L. huidobr ensis was explained completely by geographical differences. As a consequenc e of the absence of leafminer infestations on the same host plant varieties in both regions, factors governing L. trifolii population distribution dif ferences were less apparent. The presence of the same host plant varieties at both sites suggests that the two L. trifolii populations differ in host plant preference.