Genetic relationships and clonal identity in a collection of commercially relevant poplar cultivars assessed by AFLP and SSR

A collection of 66 poplar commercial clones widely cultivated in Italy, China and in other countries of southern Europe and belonging to various poplar species and hybrids, have been fingerprinted using both amplified fragment length polymorphism (AFLP) and simple sequence repeats (SSR) techniques. Three AFLP primer combinations and six SSRs unambiguously genotyped the analysed poplar collection, with the exception of three groups of six, four and two individuals, which turned out to be indistinguishable even if they met the standards currently applied for distinctness, uniformity and stability (DUS) testing when registered. High levels of variation were detected with both molecular techniques; a total of 201 AFLP bands were amplified of which 96% turned out to be polymorphic and up to 15 SSR alleles were identified at a single locus, with a mean of 9.3 alleles per locus in the case of Populus x canadensis. The probability of matching fortuitously any two genotypes at all the SSR loci in the case of R x canadensis was less then 7.5x10(-9). The AFLP-derived dendrogram and principal coordinate analysis (PCOORDA) clustered the clones with respect to their taxonomic classification, and allowed their genetic interrelationships to be established. Correct identification of poplar varieties is essential for ensuring the effective correspondence between the real and the declared identity of a clone, to avoid commercial frauds, and to establish breeding programmes. Molecular markers may play a major role to satisfy all these needs.