The wheat curl mite (WCM), Aceria tosichella Keifer, is a polyphagous eriophyoid mite and the primary vector of wheat streak mosaic virus (WSMV) and five other viral pathogens in cereals. Previous research using molecular markers and a series of laboratory experiments found A. tosichella in Australia to consist of two genetically distinct lineages, which have broad overlapping distributions and differ in their ability to transmit WSMV under controlled conditions. This pattern of transmission also appears to be apparent in the field, whereby a strong association between WSMV detection and a single WCM lineage has been detected. In this study, we conduct a population genetic analysis and provide information on the genetic structure of the Australian viruliferous WCM lineage. We assessed genetic differentiation of 16 WCM populations using nine microsatellite markers. Strong evidence for extensive gene flow and low genetic structuring throughout the Australian wheatbelt was evident, with an exception for Western Australian and far north Queensland populations that appear to be genetically isolated. The data also indicate genetic patterns consistent with an arrhenotokous parthenogenetic mode of reproduction. Implications of these findings are discussed with reference to the management of WCM and associated cereal pathogens in Australia and overseas.

The existence of genetic differences among Australian populations of the pest moth Helicoverpa armigera based on microsatellite markers is contentious. To resolve this issue, we analyzed microsatellite variation in moth samples from multiple locations simultaneously in two laboratories that have previously reported contrasting patterns. Alleles and allele numbers detected in the laboratories differed, as did the genetic differences found between the samples. The automated scoring system used in one of the laboratories combined with non-denaturing polyacrylamide gels led to inaccurate identification of alleles and high FST values between the populations. However, H. armigera in Australia is probably not structured geographically, with high gene flow between populations. This influences management of H. armigera and the development of area-wide control options, as populations need to be considered as one panmictic unit. The results also highlight potential problems of automated scoring systems when these are not checked carefully.