ISOLATION AND CHARACTERIZATION OF MICROSATELLITES IN TREMBLING ASPEN (POPULUS-TREMULOIDES)

We have identified, isolated, and characterized microsatellite/simple sequence repeat (SSR) loci in trembling aspen (Populus tremuloines) by screening partial genomic libraries. We have also examined the compat ibility and use of the P. tremuloides SSR primers to resolve microsate llites in other Populus species. Fourteen microsatellites were identif ied from 1600 clones screened. The TC/AG microsatellites were the most abundant. A total of 29 alleles were detected in 36 P. tremuloides in dividuals at the four SSR loci (two each of di-and tri-nucleotide repe ats) characterized. The number of alleles at the SSR loci ranged from 5 to 11, with an average of 7.25 alleles per locus, and the observed h eterozygosity ranged from 0.19 to 0.82, with a mean of 0.46 per locus. Although the highest polymorphism was observed for a dinucleotide SSR locus, the trinucleotide SSR loci showed substantial polymorphism. Th ere were 34 unique multilocus genotypes among the 36 P. tremuloides in dividuals examined, and 89% of the individuals had unique multilocus g enotypes. Two pairs of SSR primers were successful in PCR, amplifying genomic DNA and resolving microsatellites of comparable size from Popu lus deltoides, P. nigra, P. x canadensis, and P. maximowiczii. The mic rosatellite DNA markers developed could be used for clonal fingerprint ing, certification of controlled crosses, genome mapping, marker-assis ted early selection, genetic diversity assessments, and conservation a nd sustainable management of poplar genetic resources.