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Abstract Background The Hessian fly (Mayetiola destructor) is an important insect pest of wheat. It has tractable genetics, polytene chromosomes, and a small genome (158 Mb). Investigation of the Hessian fly presents excellent opportunities to study plant-insect interactions and the molecular mechanisms underlying genome imprinting and chromosome elimination. A physical map is needed to improve the ability to perform both positional cloning and comparative genomic analyses with the fully sequenced genomes of other dipteran species. Results An FPC-based genome wide physical map of the Hessian fly was constructed and anchored to the insect's polytene chromosomes. Bacterial artificial chromosome (BAC) clones corresponding to 12-fold coverage of the Hessian fly genome were fingerprinted, using high information content fingerprinting (HIFC) methodology, and end-sequenced. Fluorescence in situ hybridization (FISH) co-localized two BAC clones from each of the 196 longest contigs on the polytene chromosomes. An additional 70 contigs were positioned using a single FISH probe. The 266 FISH mapped contigs were evenly distributed and covered 60% of the genome (95,668 kb). The ends of the fingerprinted BACs were then sequenced to develop the capacity to create sequenced tagged site (STS) markers on the BACs in the map. Only 3.64% of the BAC-end sequence was composed of transposable elements, helicases, ribosomal repeats, simple sequence repeats, and sequences of low complexity. A relatively large fraction (14.27%) of the BES was comprised of multi-copy gene sequences. Nearly 1% of the end sequence was composed of simple sequence repeats (SSRs). Conclusion This physical map provides the foundation for high-resolution genetic mapping, map-based cloning, and assembly of complete genome sequencing data. The results indicate that restriction fragment length heterogeneity in BAC libraries used to construct physical maps lower the length and the depth of the contigs, but is not an absolute barrier to the successful application of the technology. This map will serve as a genomic resource for accelerating gene discovery, genome sequencing, and the assembly of BAC sequences. The Hessian fly BAC-clone assembly, and the names and positions of the BAC clones used in the FISH experiments are publically available at http://genome.purdue.edu/WebAGCoL/Hfly/WebFPC/.

The Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae), is the most important insect pest of wheat (Triticum aestivum L. subsp. aestivum) in the southeastern United States, and the deployment of genetically resistant wheat is the most effective control. However, the use of resistant wheat results in the selection of pest genotypes that can overcome formerly resistant wheat. We have evaluated the effectiveness of 16 resistance genes for protection of wheat from Hessian fly infestation in the southeastern United States. Results documented that while 10 of the genes evaluated could provide protection of wheat, the most highly effective genes were H12, H18, H24, H25, H26, and H33. However, H12 and H18 have been reported to be only partially effective in field evaluations, and H24, H25, and H26 may be associated with undesirable effects on agronomic traits when introgressed into elite wheat lines. Thus, the most promising new gene for Hessian fly resistance appears to be H33. These results indicate that identified highly effective resistance in wheat to the Hessian fly is a limited resource and emphasize the need to identify novel sources of resistance. Also, we recommend that the deployment of resistance in gene pyramids and the development of novel strategies for engineered resistance be considered. [ABSTRACT FROM AUTHOR]

Eighteen polymorphic microsatellite loci and 11 single-nucleotide polymorphisms were genotyped in 1 095 individual Hessian fly specimens representing 23 populations from North America, southern Europe, and southwest Asia. The genotypes were used to assess genetic diversity and interrelationship of Hessian fly populations. While phylogenetic analysis indicates that the American populations most similar to Eurasian populations come from the east coast of the United States, genetic distance is least between (Alabama and California) and (Kazakhstan and Spain). Allelic diversity and frequency vary across North America, but they are not correlated with distance from the historically documented point of introduction in New York City or with temperature or precipitation. Instead, the greatest allelic diversity mostly occurs in areas with Mediterranean climates. The microsatellite data indicate a general deficiency for heterozygotes in Hessian fly. The North American population structure is consistent with multiple introductions, isolation by distance, and human-abetted dispersal by bulk transport of puparia in infested straw or on harvesting equipment. [ABSTRACT FROM AUTHOR]

An integral part to understanding the biology of an invasive species is determining its origin, particularly in pest species. As one of the oldest known invasive species, the goals of this study were to evaluate the evidence of a westward expansion of Hessian fly into North America, from a potential singular introduction event, and the population genetic structure of current populations. Levels of genetic diversity and population structure in the Hessian fly were compared across North America, Europe, North Africa, Western Asia, and New Zealand. Furthermore, Old World populations were evaluated as possible sources of introduction. We tested diversity and population structure by examining 18 microsatellite loci with coverage across all four Hessian fly chromosomes. Neither genetic diversity nor population genetic structure provided evidence of a westward movement from a single introduction in North America. Introduced populations in North America did not show identity or assignment to any Old World population, likely indicating a multiple introduction scenario with subsequent gene flow between populations. Diversity and selection were assessed on a chromosomal level, with no differences in diversity or selection between chromosomes or between native and introduced populations. [ABSTRACT FROM AUTHOR]

Background: The Hessian fly (Mayetiola destructor) is an important insect pest of wheat. It has tractable genetics, polytene chromosomes, and a small genome (158 Mb). Investigation of the Hessian fly presents excellent opportunities to study plant-insect interactions and the molecular mechanisms underlying genome imprinting and chromosome elimination. A physical map is needed to improve the ability to perform both positional cloning and comparative genomic analyses with the fully sequenced genomes of other dipteran species. Results: An FPC-based genome wide physical map of the Hessian fly was constructed and anchored to the insect's polytene chromosomes. Bacterial artificial chromosome (BAC) clones corresponding to 12-fold coverage of the Hessian fly genome were fingerprinted, using high information content fingerprinting (HIFC) methodology, and end-sequenced. Fluorescence in situ hybridization (FISH) co-localized two BAC clones from each of the 196 longest contigs on the polytene chromosomes. An additional 70 contigs were positioned using a single FISH probe. The 266 FISH mapped contigs were evenly distributed and covered 60% of the genome (95,668 kb). The ends of the fingerprinted BACs were then sequenced to develop the capacity to create sequenced tagged site (STS) markers on the BACs in the map. Only 3.64% of the BAC-end sequence was composed of transposable elements, helicases, ribosomal repeats, simple sequence repeats, and sequences of low complexity. A relatively large fraction (14.27%) of the BES was comprised of multi-copy gene sequences. Nearly 1% of the end sequence was composed of simple sequence repeats (SSRs). Conclusion: This physical map provides the foundation for high-resolution genetic mapping, map-based cloning, and assembly of complete genome sequencing data. The results indicate that restriction fragment length heterogeneity in BAC libraries used to construct physical maps lower the length and the depth of the contigs, but is not an absolute barrier to the successful application of the technology. This map will serve as a genomic resource for accelerating gene discovery, genome sequencing, and the assembly of BAC sequences. The Hessian fly BAC-clone assembly, and the names and positions of the BAC clones used in the FISH experiments are publically available at http://genome.purdue.edu/WebAGCoL/Hfly/WebFPC/. [ABSTRACT FROM AUTHOR]

A microsatellite library was prepared from size-selected genomic DNA of Hessian fly ( Mayetiola destructor). Approximately 81% of recovered clones hybridized with microsatellite motif-specific probes. Subsequently, 2350 clones were sequenced. Sixty-two individual flies from laboratory strains were used to test for reliability and polymorphism in 50 of the microsatellites by gel electrophoresis; 18 were further tested with capillary electrophoresis. Of these, 17 behaved as a polymorphic single locus appropriate for population analysis. [ABSTRACT FROM AUTHOR]