CHARACTERIZATION OF SOLANUM-TUBEROSUM SIMPLE SEQUENCE REPEATS AND APPLICATION TO POTATO CULTIVAR IDENTIFICATION

With the continued introduction of new potato cultivars, accurate iden tification is becoming difficult but is essential for maintaining cult ivar integrity and Plant Breeders' Rights. Hypervariable DNA sequences , referred to as simple sequence repeats (SSRs) or microsatellites, ha ve been reported to be an excellent source of genetic markers. To dete rmine the abundance, distribution, and composition of SSRs within Sola num tuberosum, 252 sequences were searched for tetranucleotide and sma ller SSRs with a minimum length of 20 nucleotides and a maximum discre pancy of two nucleotides. In total, 40 unique SSRs were observed in th e 252 S. tuberosum sequences examined and occurred at a frequency of o ne SSR every 8.1 kb. To assess the ability of site-specific amplified SSRs to identify potato cultivars, a simple (TCAC)(m) and compound (TC AC)(m) .(CTT)(n) SSR 5' to the starch synthase gene and a compound (C) (p) .(CT)(q) . (AT)(r) .(G)(s) SSR 5' to the sequence encoding mature proteinase inhibitor I, were examined and shown to produce unique DNA profiles for 73 of 95 tetraploid cultivars. In total, 24 alleles were observed at these loci and the accurately sized amplified DNA products can be used to establish a database for cultivar identification. Site -specific amplified alleles were somatically stable and have been cons erved in clonal variants of Russet Burbank independently maintained fo r almost seven decades, a characteristic essential for cultivar identi fication. As genetic markers, the abundant, informative, and easily ex amined site-specific amplified alleles of SSRs are ideal for quickly a nd accurately determining cultivar identity of S. tuberosum ssp. tuber osum.