Genetic Characterization of North American Populations of the Wheat Curl Mite and Dry Bulb Mite Gary L

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Faculty Publications: Department of Entomology Entomology, Department of 10-2012 Genetic Characterization of North American Populations of the Wheat Curl Mite and Dry Bulb Mite Gary L. Hein University of Nebraska-Lincoln, [email protected] Roy French USDA-Agricultural Research Service and University of Nebraska-Lincoln Benjawan Siriwetwiwat University of Nebraska-Lincoln James W. Amrine West Virginia University, [email protected] Follow this and additional works at: http://digitalcommons.unl.edu/entomologyfacpub Part of the Agriculture Commons, Entomology Commons, Food Science Commons, and the Plant Pathology Commons Hein, Gary L.; French, Roy; Siriwetwiwat, Benjawan; and Amrine, James W., "Genetic Characterization of North American Populations of the Wheat Curl Mite and Dry Bulb Mite" (2012). Faculty Publications: Department of Entomology. 567. http://digitalcommons.unl.edu/entomologyfacpub/567 This Article is brought to you for free and open access by the Entomology, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Faculty Publications: Department of Entomology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. This article is a US government work and is not subject to copyright in the United States. MOLECULAR ENTOMOLOGY Genetic Characterization of North American Populations of the Wheat Curl Mite and Dry Bulb Mite 1,2 3 1 4 GARY L. HEIN, ROY FRENCH, BENJAWAN SIRIWETWIWAT, AND JAMES W. AMRINE J. Econ. Entomol. 105(5): 1801Ð1808 (2012); DOI: http://dx.doi.org/10.1603/EC11428 ABSTRACT 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 two distinct types within A. tosichella were 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 separation with A. tulipae, suggesting that species scale differences exist between 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. KEY WORDS Aceria tosichella, Aceria tulipae, wheat curl mite, wheat streak mosaic Wheat streak mosaic has long been considered the complex signiÞcantly impacts wheat (Tatineni et al. most serious disease of winter wheat (Triticum aesti- 2010, Byamukama et al. 2012). vum L.) in the western Great Plains (Brakke 1987). As with most arthropod-transmitted pathogens, However, the wheat curl mite, Aceria tosichella Keifer, management of the virus complex focuses on manag- has now been shown to transmit three serious viruses, ing the vector. The most prevalent problems with this wheat streak mosaic virus (WSMV), high plains virus disease complex arise when hail shells out seeds from (HPV), and Triticum mosaic virus (TriMV) to wheat headed wheat just before harvest, and the fallen seeds throughout the Great Plains (Slykuis 1955; Seifers et quickly germinate and produce volunteer wheat al. 1997, 2008). HPV was identiÞed from wheat and (Brakke 1987, Wegulo et al. 2008). This volunteer corn throughout the Great Plains in the mid-1990s wheat is rapidly infested with mites moving from the (Jensen and Lane 1994, Jensen et al. 1996), and TriMV maturing wheat and serves as a Ôgreen bridgeÕ to carry was recently identiÞed from wheat in Kansas (Seifers both the mite and viruses through the summer to infest et al. 2008). Because the wheat curl mite transmits all and infect the newly emerging winter wheat in the fall. of these viruses, they are often found together in Cultural control practices are targeted at breaking the mixed infections in the Þeld (Mahmood et al. 1998, green bridge by eliminating volunteer wheat, and Seifers et al. 2008). The extent of the interaction of the thus, reducing the potential for fall infections viruses is not known; however, it is clear that where (Wegulo et al. 2008, Hein 2010). Often, environmental one or more viruses are present, the resulting disease conditions make volunteer wheat control problem- atic, and the disease potential persists. In addition, 1 University of Nebraska-Lincoln, Department of Entomology, Box other alternate summer hosts for the mites and viruses 830933, Lincoln, NE 68583-0933. (e.g., corn, potentially several other grass hosts) can 2 Corresponding author, e-mail: [email protected]. function as the green bridge to establish infections in 3 United States Department of Agriculture-Agricultural Research the fall (Wegulo et al. 2008). Service and Department of Plant Pathology, University of Nebraska- Lincoln, Lincoln, NE. The signiÞcant impact of this disease in Great Plains 4 West Virginia University, Morgantown, WV. winter wheat has resulted in a good deal of work being 1802 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 105, no. 5 done to identify virus- and mite-resistant germplasm. Abacarus hystrix (Nalepa) were identiÞed using mo- The Þrst wheat curl mite resistance gene that became lecular genetics techniques and veriÞed by using host widely used commercially originated from a translo- and morphological data (Skoracka et al. 2002, Sko- cation of rye into wheat and was deployed in the racka and Dabert 2010). Alternatively, examinations cultivar ÔTAM 107Ј (Martin et al. 1984). TAM 107, and of genetic variation for Aceria cajani Channabasa- a few other varieties with the same gene, were planted vanna from pigeonpea in India and the surrounding widely in the central Great Plains in the late 1980s and region demonstrated little variability (Kumar et al. 1990s, but in the mid-1990s, wheat curl mite popula- 2001). For A. tosichella, recent molecular character- tions in the region were found to have overcome this izations have shown haplotype differences in Australia resistance gene (Harvey et al. 1995, 1997). Several (Carew et al. 2009). additional genes for resistance to wheat curl mite More complete characterization of A. tosichella colonization have been identiÞed from several wheat populations may enhance our understanding of the relatives and transferred into wheat (Conner et al. relationship of this mite to its hosts and also to the 1991, Li et al. 2002). viruses that they transmit. Seifers et al. (2002), using A major drawback to widespread deployment of mostly the same wheat curl mite populations that most of these resistant genes is that the reaction to Harvey et al. (1999) used to demonstrate biotypic these genes is inconsistent and dependent on the differences, demonstrated differential transmission of source of mites tested. Harvey et al. (1999) found a HPV by these various mite populations. They also varied response to seven sources of resistance to found that these Þve populations of wheat curl mites wheat curl mite found in wheat when comparing Þve all transmitted WSMV. However, Schiffer et al. (2009) geographically distinct mite populations (Nebraska, identiÞed two distinct strains of A. tosichella in Aus- South Dakota, Montana, Texas, and Alberta, Canada). tralia and found that they differ in their ability to They also found a varied response when comparing transmit WSMV. Transmission of TriMV by wheat curl eight mite populations from across Kansas. Malik et al. mite has been demonstrated (Seifers et al. 2009), but (2003) also found biotypic differences between pop- the inßuence of mite populations on transmission has ulations of wheat curl mite when comparing diverse not been fully investigated. However, preliminary germplasm. These differences between mite popula- data indicates that differential transmission by differ- tions in response to resistance genes have serious ent A. tosichella populations may also occur (G.L.H., implications to gene deployment and managing these unpublished data). This variable capacity of mite pop- genes to avoid further wheat curl mite biotype devel- ulations to transmit HPV and perhaps TriMV has im- opment. portant implications on the epidemiology and man- Differences in response to mite resistance genes are agement of this virus complex. not surprising in light of the historic record of serious Because of the demonstrated importance of

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