title: A molecular method for S-allele identification in apple based on allele-specific PCR.
abstract: cDNA sequences corresponding to two self-incompatibility alleles (S-alleles) of the apple cv 'Golden Delicious' have previously been described, and now we report the identification of three additional S-allele cDNAs of apple, one of which was isolated from a pistil cDNA library of cv 'Idared' and two of which were obtained by reverse transcription-PCR (RT-PCR) on pistil RNA of cv 'Queen's Cox'. A comparison of the deduced amino acid sequences of these five S-allele cDNAs revealed an average homology of 69%. Based on the nucleotide sequences of these S-allele cDNAs, we developed a molecular technique for the diagnostic identification of the five different S-alleles in apple cultivars. The method used consists of allele-specific PCR amplification of genomic DNA followed by digestion of the amplification product with an allele-specific restriction endonuclease. Analysis of a number of apple cultivars with known S-phenotype consistently showed coincidence of phenotypic and direct molecular data of the S-allele constitution of the cultivars. It is concluded that the S-allele identification approach reported here provides a rapid and useful method to determine the S-genotype of apple cultivars.
authors.affiliation: F. A. Janssens Laboratory of Genetics, Katholieke Universiteit Leuven, W. de Croylaan 42, B-3001, Leuven, Belgium.
authors.forename: G A
authors.initials: GA
authors.lastname: Janssens
authors.forename: I J
authors.initials: IJ
authors.lastname: Goderis
authors.forename: W F
authors.initials: WF
authors.lastname: Broekaert
authors.forename: W
authors.initials: W
authors.lastname: Broothaerts