MOLECULAR ENTOMOLOGY Genetic Characterization of North American Populations of the Wheat Curl Mite and Dry Bulb Mite

The wheat curl mite, Aceria tosichella Keifer, transmits at least three harmful viruses, wheat streak mosaic virus (WSMV), high plains virus (HPV), and Triticum mosaic virus (TriMV) to wheat (Triticum aestivum L.) throughout the Great Plains. This virus complex is considered to be the most serious disease of winter wheat in the western Great Plains. One component of managing this disease has been developing mite resistance in wheat; however, identiÞcation of mite biotypes has complicated deployment and stability of resistance. This biotypic variability in mites and differential virus transmission by different mite populations underscores the need to better understand mite identity. However, A. tosichella has a history of serious taxonomic confusion, especially as it relates to A. tulipae Keifer, the dry bulb mite. Molecular techniques were used to genetically characterize multiple A. tosichella populations and compare them to populations of A. tulipae. DNA from these populations was polymerase chain reaction ampliÞed and the ribosomal ITS2 region sequenced and compared.These results indicated limited variability between these two species, but twodistinct types within A. tosichellawere found that corresponded to previous work with Australian mite populations. Further work using sequencing of several mitochondrial DNA genes also demonstrated two distinct types of A. tosichella populations. Furthermore, the separation between these two A. tosichella types is comparable to their separationwithA. tulipae, suggesting that species scaledifferencesexistbetween these two types of A. tosichella. These genetic differences correspond to important biological differences between the types (e.g., biotypic and virus transmission differences). In light of these differences, it is important that future studies on biological response differences account for these mite differences.