DEVELOPMENT OF SEX-LINKED PCR MARKERS FOR GENDER IDENTIFICATION IN ACTINIDIA

Two sex-linked random amplified polymorphic DNA (RAPD) markers identif ied from Actinidia chinensis were converted into sequence-characterise d amplified regions (SCARs) for the large-scale screening of Actinidia breeding populations. Initial SCAR primers converted one RAPD (SmX) i nto a dominant marker, but the other (SmY), which was potentially more useful because of its linkage to the male determining 'Y' locus, fail ed to retain polymorphism. This difficulty was overcome by cloning and sequencing the alternate 'allele' from female plants, and then design ing 'allele'-specific primers that utilised nucleotide differences bet ween the sexes. Using a quick squash-blot method of DNA extraction, th e SCAR primers were tested in 120 A. chinensis plants to determine the ir gender. The system is now in use for large-scale screening of seedl ing populations in the Actinidia breeding programme. The sex-linked SC AR primers also functioned with plants from some other geographically separate accessions of A. chinensis and with plants in the closely rel ated polyploid species A. deliciosa, but did not amplify a sex-linked band in more distantly related species of Actinidia.