Preliminary linkage map of the Turkey (Meleagris gallopavo) based on microsatellite markers D. W. Burt*, D. R. Morrice*, A. Sewalem † , J. Smith*, I. R. Paton*, E. J. Smith ‡ , J. Bentley § and P. M. Hocking † *Department of Genomics and Bioinformatics, † Department of Genetics and Biometry, Roslin Institute (Edinburgh), Roslin, Midlothian, UK. ‡ Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA. § British United Turkeys, Warren Hall, Broughton, Chester, UK Summary The turkey is an agriculturally important species for which, until now, there is no published genetic linkage map based on microsatellite markers – still the markers most used in the chicken and other farm animals. In order to increase the number of markers on a turkey genetic linkage map we decided to map new microsatellite sequences obtained from a GT- enriched turkey genomic library. In different chicken populations more than 35–55% of microsatellites are polymorphic. In the turkey populations tested here, 43% of all turkey primers tested were found to be polymorphic, in both commercial and wild type turkeys. Twenty linkage groups (including the Z chromosome) containing 74 markers have been established, along with 37 other unassigned markers. This map will lay the foundations for further genetic mapping and the identification of genes and quantitative trait loci in this economically important species. Genome comparisons, based on genetic maps, with related species such as the chicken would then also be possible. All primer information, polymerase chain reaction (PCR) conditions, allele sizes and genetic linkage maps can be viewed at http://roslin.thearkdb.org/. The DNA is also available on request through the Roslin Institute. Keywords enriched library, linkage map, microsatellite markers, turkey. Introduction The turkey (Meleagris gallopavo) is a member of the Galli- formes group of birds with a diploid number of chromo- somes, 2n ¼ 80. The karyotype is very similar to that of the chicken (Gallus gallus), which has one less pair of macro- chromosomes (2n ¼ 78) (Ryttman & Tegelstro ¨m 1981; Stock & Bunch 1982). The equivalent of chicken chromo- some 2 is split into two individual chromosomes in the turkey (Schmid et al. 2000). Although genetic linkage maps have been well developed in the chicken, little exists in the turkey, although resources have been developed (Huang et al. 1999; Reed et al. 2000a; Smith et al. 2001; Dranchak et al. 2003) and a preliminary genetic map based on RFLP markers has been reported (Harry et al. 2001; http:// www.tc.umn.edu/reedx054/Turkeygenome.htm). The use of microsatellites isolated in chicken for mapping in turkeys has had limited success, with only 10–20% (Levin et al. 1995; Liu et al. 1996; Reed et al. 2000b) of chicken sequences being polymorphic in the turkey families tested. In order to increase the number of markers on a turkey genetic linkage map we decided to map new microsatellite sequences obtained from a GT-enriched turkey genomic library. Materials and methods Backcross reference families The Roslin (ROS) backcross families were derived from crosses between Nebraska Spot (maintained at the Roslin Institute) and Large White turkeys called BUT T5 (supplied by British United Turkeys Ltd, Chester, UK). F 1 progeny were generated from mating eight Nebraska Spot sires each to one BUT dam. Reciprocal backcross families were created either from six Nebraska Spot parental F 0 sires mated to one of their F 1 daughters or six F 1 males mated to one of their parental BUT F 0 dams. The largest backcross families ROS-5 Address for correspondence David W. Burt, Department of Genomics and Bioinformatics, Roslin Institute (Edinburgh), Roslin, Midlothian EH25 9PS, UK. E-mail: dave.burt@bbsrc.ac.uk Accepted for publication 25 June 2003 Ó 2003 International Society for Animal Genetics, Animal Genetics, 34, 399–409 399