Plant & Animal Genome VI Conference

W29

TOWARDS SECOND-GENERATION LINKAGE MAPS IN CONIFERS: A GENETIC MAP OF NORWAY SPRUCE (Picea abies K.) INCLUDING 61 SSR MARKERS

Dipartimento di Produzione Vegetale e Tecnologie Agrarie, Università degli Studi di Udine, I-33100 Udine, Italy

Genetic linkage maps have been produced for a wide range of organisms thanks to the steadily increasing availability of molecular markers in the last decade. A break-through has been represented by the use of microsatellites (SSRs) as genetic markers which has led to the construction of the so called second-generation genetic maps in humans, mouse and other organisms of major importance. We constructed a second-generation single-tree genetic linkage map of Norway spruce (Picea abies K.) using a panel of 72 haploid megagametophytes with a total of 447 segregating bands (366 AFLPs, 20 SAMPLs and 61 SSRs, each single band being treated initially as a dominant marker). Four hundred and thirteen markers where mapped in 29 linkage groups (including triplets and doublets) covering a genetic length of 2198.3 cM which represents the 77.4 % of the estimated genome length of Picea abies (approximately 2839 cM). Thirty-eight SSR marker loci could be mapped onto 19 linkage groups. The map appears to be still far from coalescing into the expected 12 chromosomal linkage groups of Norway spruce (2n=3D 2x=3D=24). Analysis of the distribution of the markers in the framework map showed that they are not randomly distributed, possibly as a consequence of the bias of the marker set towards single- or low-copy DNA sequences in a species whose genome is characterised by a very large size and a high proportion of repetitive DNA. PCR-based multiplex marker assays such as AFLP and SAMPL have shown to be the class of markers which provides the easiest and fastest wayto establish a framework map in which SSR markers can be mapped. This set of highly informative Sequence Tagged Sites (STSs) can be used in many aspects of genetic analysis of forest trees, such as marker assisted selection, QTL mapping, positional cloning, gene flow analysis, mating system analysis, genetic diversity studies.