PRELIMINARY GENETIC ANALYSIS OF RAINBOW TROUT SEX CHROMOSOMES

¹ Department of Biological Sciences Northern Arizona University Flagstaff, AZ 86011

² School of Biological Sciences Washington State University Pullman, WA 99164

Rainbow trout could be an important model of early vertebrate sex chromosome evolution. The sex chromosomes of this species appear to be in the early stages of differentiation with morphologically differentiated sex chromosomes present in some populations and absent in others. Comparing the genetic structure of the sex chromosomes in these evolutionarily divergent populations will provide insights into the structural changes associated with the evolution of heteromorphic sex chromosomes in vertebrates. Male and female pools were used in Bulked Segregant Analysis (BSA) to identify markers in the target region on the linkage group containing the sex determination locus (Sex). This strategy utilized DNA pools constructed using genotype information that, in contrast to phenotypic data, exclusively defined the region of interest. A total of 512 AFLP primer combinations were screened resulting in 44 potentially sex-linked markers. These markers were subsequently analyzed in a mapping panel of 46 androgenetically-derived doubled haploid (DH) rainbow trout. Twenty-eight markers segregated to the sex chromosomes, 12 mapped to other regions of the genome and 4 were not resolvable and were likely artifacts. None of these markers were absolutely linked to sex in this family. The complete map of this linkage group contains 34 markers including the Sex locus. The utility of this genotypic-based BSA strategy for identifying markers in specific genomic regions will be discussed.