Development and characterization of DNA markers for two avian species
Central to the application of genomics to animal agriculture are DNA markers, especially microsatellites and single nucleotide polymorphisms. These markers are the resources necessary for constructing genetic maps and for determining how improved and unimproved animal breeds are related. Here, DNA markers were developed for two avian species, the turkey, Meleagris gallopavo, and the budgerigar (budgie), Melopsittacus undulatus. Genomic libraries enriched for simple sequence repeats were used to generate about 70 budgie sequences of a total length of 38 kb. From these sequences, 9 primer pairs were designed and used to screen for informativeness in a panel of DNA samples from unrelated budgie samples. All but one of the nine primers evaluated were polymorphic with the number of alleles ranging from two to four. Comparative analysis involving the use of these budgie primers showed moderate sequence similarity to turkey and chicken. The genomic libraries and the comparative sequences provide useful genomic reagents that could be used to construct a budgie genome map. In the turkey, ten previously described microsatellites and a gene-based single nucleotide polymorphism (SNP) were used to evaluate the relatedness of heritage varieties to a commercial strain. Estimates of Nei's genetic distance (D) and genetic differentiation (Rst) between populations using microsatellite markers showed that the commercial strain is genetically more closely related to the Bourbon Red and Narragansett and least related to the Royal palm and Spanish Black. Gene flow (Nm) level was highest between the commercial and Bourbon Red populations. The SNP analysis by PCR-RFLP revealed that the commercial strain was more closely related to the Spanish black and Narragansett and least related to the Bourbon red and Blue slate. Though results of the two marker systems, microsatellite and SNP, were inconsistent, they provide insights into using heritage turkeys to genetically improve commercial populations by introgression. The present thesis investigation showed that DNA markers provide a strong opportunity to develop genomic reagents needed to test hypotheses in little-studied agriculturally important and model avian species.