Genetic Diversity in Laboratory Colonies of Western Corn Rootworm (Coleoptera: Chrysomelidae), Including a Nondiapause Colony

USDA-ARS, Corn Insects and Crop Genetics Research Unit, Genetics Laboratory, Iowa State University, Ames, IA 50011, USA.
Environmental Entomology (Impact Factor: 1.3). 07/2007; 36(3):637-45. DOI: 10.1603/0046-225X(2007)36[637:GDILCO]2.0.CO;2
Source: PubMed


Laboratory-reared western corn rootworms, Diabrotica virgifera virgifera, from colonies maintained at the North Central Agricultural Research Laboratory (NCARL) in Brookings, SD, are used extensively by many researchers in studies of the biology, ecology, behavior, and genetics of this major insect pest. A nondiapause colony developed through artificial selection in the early 1970s is particularly attractive for many studies because its generation time is much shorter than that of typical diapause colonies. However, the nondiapause colony has been in culture for ≈190 generations without out-crossing. We compared variation at six microsatellite loci among individuals from the NCARL nondiapause colony (≈190 generations), main diapause colony (≈22 generations), four regional diapause colonies (3–8 generations), and four wild populations. Genetic diversity was very similar among the diapause laboratory colonies and wild populations. However, the nondiapause colony showed ≈15–39% loss of diversity depending on the measure. Pairwise estimates of F
ST were very low, revealing little genetic differentiation among laboratory colonies and natural populations. The nondiapause colony showed the greatest genetic differentiation with an average pairwise F
ST of 0.153. There was little evidence that the laboratory colonies had undergone genetic bottlenecks except for the nondiapause colony. The nondiapause colony has suffered a moderate loss in genetic diversity and is somewhat differentiated from wild populations. This was not unexpected given its history of artificial selection for the nondiapause trait, and the large number of generations in culture. In contrast, the results indicate that the diapause colonies maintained at NCARL are genetically similar to wild populations.

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    • "Finally, there is little evidence for a significant reduction of genetic diversity among lab populations, suggesting that maintenance in artificial environments has not caused an erosion of genetic diversity. This finding mirrors observations by Kim et al. [55], who compared a laboratory population derived from the non-diapause Brookings population to field populations using microsatellite markers. "
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    ABSTRACT: Western corn rootworm (WCR) is one of the most significant insect pests of maize in North America. WCR has dramatically increased its range in the last century, invading key maize production areas in the US and abroad. In addition, this species has a history of evolving traits that allow it to escape various control options. Improved genetic and genomic resources are crucial tools for understanding population history and the genetic basis of trait evolution. Here we produce and analyze a transcriptome assembly for WCR. We also perform whole genome population resequencing, and combine these resources to better understand the evolutionary history of WCR. The WCR transcriptome assembly presented here contains approximately 16,000 unigenes, many of which have high similarity to other insect species. Among these unigenes we found several gene families that have been implicated in insecticide resistance in other species. We also identified over 500,000 unigene based SNPs among 26 WCR populations. We used these SNPs to scan for outliers among the candidate genes, and to understand how population processes have shaped genetic variation in this species. This study highlights the utility of transcriptomic and genomic resources as foundational tools for dealing with highly adaptive pest species. Using these tools we identified candidate gene families for insecticide resistance and reveal aspects of WCR population history in light of the species' recent range expansion.
    BMC Genomics 03/2014; 15(1):195. DOI:10.1186/1471-2164-15-195 · 3.99 Impact Factor
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    • "This difference between laboratory strains and wild populations/field samples has already been explored and demonstrated in other species. For instance, Kim et al. [63] observed a loss of 15–39% genetic diversity in the non-diapause colony of the western corn rootworm (Diabrotica virgifera virgifera Le Conte, 1868) compared with contemporary wild populations, depending on the parameter measured. Similar results were obtained by Coe et al. [64] with the zebrafish (Danio rerio Hamilton, 1863) with the allelic richness for all four strains less than 20% of that found in the wild fish. "
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    ABSTRACT: The pinewood nematode, Bursaphelenchus xylophilus, native to North America, is the causative agent of pine wilt disease and among the most important invasive forest pests in the East-Asian countries, such as Japan and China. Since 1999, it has been found in Europe in the Iberian Peninsula, where it also causes significant damage. In a previous study, 94 pairs of microsatellite primers have been identified in silico in the pinewood nematode genome. In the present study, specific PCR amplifications and polymorphism tests to validate these loci were performed and 17 microsatellite loci that were suitable for routine analysis of B. xylophilus genetic diversity were selected. The polymorphism of these markers was evaluated on nematodes from four field origins and one laboratory collection strain, all originate from the native area. The number of alleles and the expected heterozygosity varied between 2 and 11 and between 0.039 and 0.777, respectively. First insights into the population genetic structure of B. xylophilus were obtained using clustering and multivariate methods on the genotypes obtained from the field samples. The results showed that the pinewood nematode genetic diversity is spatially structured at the scale of the pine tree and probably at larger scales. The role of dispersal by the insect vector versus human activities in shaping this structure is discussed.
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    • "We purchased 10,000 eggs from each origin, reared the larvae on isoline corn, and conducted reciprocal crosses with adults from a non-diapausing colony [47] to increase the number of generations per year from one to at least four. The wild-type genes were introgressed because the non-diapausing colony has been maintained in the laboratory for more than 200 generations and has lost genetic variation [48]. Combining eggs from the two reciprocal crosses yielded 1,357 adults from MN, 2,448 adults from WI and 8,220 adults from KS. "
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