CHARACTERIZATION OF HIGHLY VARIABLE (GA CT)(N) MICROSATELLITES IN THEBUR OAK, QUERCUS-MACROCARPA/

The objective of this study was to ascertain the usefulness of polymer ase chain reaction (PCR)-based microsatellite analysis for studying po llination and parentage in a wind-pollinated temperate tree. A small i nsert genomic library of the bur oak (Quercus macrocarpa) was construc ted and screened for the presence of(CA/GT)(n), and (GA/CT)(n) repeats . The proportion of positive clones yielded estimates of 3 x 10(5) suc h dinucleotide repeats per genome, roughly comparable to abundances re ported in other eukaryotic genomes. Thirteen positive clones were sequ enced. In contrast to mammalian genomes, the (CA/CT)(n), motif was mor e abundant than the (CA/GT)(n), motif in these clones. The (GA/CT)(n), repeats also showed longer average repeat length (mean n=16.2 versus 7.3), suggesting that they are better candidates for yielding polymorp hic genetic markers in oak genomes. Indeed, a survey of adult bur oaks and offspring in a small stand in northern Illinois at 3 of these (GA /CT)(n), microsatellite loci revealed Mendelian inheritance and extrem ely high levels of polymorphism, with the number of alleles at each lo cus ranging from 11-20 and heterozygosity ranging from 0.66 to 0.75. T hese results, indicating that (GA/CT)(n) microsatellites are both abun dant and highly polymorphic in the bur oak genome, suggest that such g enetic markers have tremendous potential for applications for studies of parentage, pollination and dispersal in temperate trees.