Comparative genome and QTL mapping between maritime and loblolly pines

Genetic markers developed from expressed sequence tags (ESTs) were used as orthologous loci for comparative genome studies in the genus Pinus. A total of 309 ESTs derived from conifer gene sequences were tested for amplification and polymorphism in maritime pine (Pinus pinaster Ait.). Electrophoresis-based techniques made it possible to map 50 expressed sequence tag polymorphisms (ESTPs). The map positions of 32 markers were compared to putative orthologous loci on the loblolly pine (Pinus taeda L.) linkage map, which is the reference map of the conifer genetic mapping community. Overall, synteny was maintained between the two species. This report agrees with other pairwise genome comparisons in pine and supports the cytogenetic evidence that chromosome evolution in the genus is conservative. The alignment of homologous linkage groups allowed, for the first time in conifers, the comparison of QTL location. The position of two QTLs controlling wood density and cell wall components were found to be conserved between the two species.