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

A simple procedure is described that is capable of determining the gen etic sex of chinook salmon (Oncorhynchus tshawytscha). The test was de veloped by sequencing a Y-chromosomal DNA probe (OtY1) from this speci es and designing oligonucleotides for use in polymerase chain reaction s (PCR). The PCR produces a male-specific fragment of 209 bp and sever al other non-sex-specific fragments of higher molecular weight. The pa ttern obtained from the PCR suggests that the Y-chromosome-specific fr agments are repeated in the genome, consistent with previous observati ons made with Southern blot analysis. The assay can be rapidly and rel iably performed on small pieces of tissue or a small drop of blood, th us obviating the need to sacrifice the animal. The assay for Y-chromos omal DNA was used to determine the genetic sex of precociously mature, androgen-treated chinook salmon. Both XX males and regular XY males w ere 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 s tocks for aquacultural purposes.