Comparative genome mapping among Populus adenopoda, P. alba, P. deltoides, P. euramericana and P. trichocarpa

Among the genus Populus, the sections Populus (white poplar), Aigeiros Duby (black poplar) and Tacamahaca Spach contain many tree species of economical and ecological important properties. Two parental maps for the inter-specific hybrid population of Populus adenopoda x P. alba (two species of Populus section) were constructed based on SSR and SRAP markers by means of a two-way pseudo-test cross mapping strategy. The same set of SSR markers developed from the P. trichocarpa (belonging to Tacamahaca section) genome which were used to construct the maps of P. deltoides and P. euramericana (two species of Aigeiros section) was chosen to analyze the genotype of the experimental population of P. adenopoda x P. alba. Using the mapped SSR markers as allelic bridges, the alignment of the white and black poplar maps to each other and to the P. trichocarpa physical map was conducted. The alignment showed high degree of marker synteny and colinearity and the closer relationship between Aigeiros and Tacamahaca sections than that of Populus and Tacamahaca. Moreover, there was evidence for the chromosomal duplication and inter-chromosomal reorganization involving some poplar linkage groups, suggesting a complicated course of fission or fusion in one of the lineages. A poplar consensus map based on the comparisons could be constructed will be useful in practical applications including marker assisted selection.