A RAPID PCR-BASED TEST FOR Y-CHROMOSOMAL DNA ALLOWS SIMPLE PRODUCTION OF ALL-FEMALE STRAINS OF CHINOOK SALMON

A simple procedure is described that is capable of determining the genetic sex of chinook salmon (Oncorhynchus tshawytscha). The test was developed by sequencing a Y-chromosomal DNA probe (OtY1) from this species and designing oligonucleotides for use in polymerase chain reactions (PCR). The PCR produces a male-specific fragment of 209 bp and several other non-sex-specific fragments of higher molecular weight. The pattern obtained from the PCR suggests that the Y-chromosome-specific fragments are repeated in the genome, consistent with previous observations made with Southern blot analysis. The assay can be rapidly and reliably performed on small pieces of tissue or a small drop of blood, thus obviating the need to sacrifice the animal. The assay for Y-chromosomal DNA was used to determine the genetic sex of precociously mature, androgen-treated chinook salmon. Both XX males and regular XY males were identified. Progeny obtained from these and control crosses showed that, as expected, fish positive for Y-chromosomal DNA produced both males and females, whereas those appearing negative for Y-chromosomal DNA produced only females. The application of such simple tests for Y-chromosomal DNA in fish should facilitate the development of monosex stocks for aquacultural purposes.