Published online by Cambridge University Press: 16 March 2011
Apple cultivars are an integral part of the Latvian State Program for Preservation and Sustainable Use of Genetic Resources for Food and Agriculture. Latvian apple (n = 109) cultivars of local origin, nominated as National Plant Genetic Resources, were analyzed with eight simple sequence repeat (SSR) markers recommended by the European Cooperative Programme for Plant Genetic Resources (ECPGR) Malus/Pyrus working group and a marker for scab resistance gene (Vf). All SSR loci exhibited a high level of polymorphism – 12 to 39 alleles, 18.75 in average, with high observed heterozygosity (Ho) ranging from 0.64 to 0.89 and a mean of 0.78. The gene diversity (polymorphism information content value) varied from 0.79 to 0.90, with an average of 0.86. All cultivars could be distinguished with the tested set of SSR loci, with a high frequency of rare (38%) or unique (26%) alleles. For the Vf gene, all three possible genotypes (VfVf, Vfvf and vfvf) were detected for 1, 6 and 102 varieties, respectively. The analyzed germplasm showed high genetic diversity, particularly landraces, while the modern cultivars clustered mainly into two groups. Cluster analysis did not reveal a clear pattern with well-defined groups, but confirmed some relationships based on known or putative pedigrees, as well as suggesting the possible parentage of some cultivars.