We have constructed an aspen (Populus tremuloides Michx., line Turesson141) BAC library containing 55,296 clones in total. A random sampling of 86 BAC clones indicated an average insert size of 76 kb with a range of 20 to 160 kb. Twelve percent of the BAC clones in the library have an insert size larger than 100 kb. Based on an estimated genome size for Populus of 500 Mbp, library coverage is about 8 haploid genome equivalents. This library will be screened using AFLP marker identified before co-segregating with gender in a P. tremula x P. tremuloides progeny, where Turesson141 was the male parent.
A major concern over the use of transgenic trees is the potential for transgene dispersal through pollen and seeds. The incorporation of sterility inducing genes into transgenic lines of trees has been proposed to reduce or even avoid gene flow of transgenes into non-transgenic interbreeding species. The evaluation of strategies for the induction of sterility in transgenic forest tree species has been hindered by their long vegetative phases. In this study an early flowering 35S::Leafy poplar line was used for the faster evaluation of the sterility construct C-GPDHC::Vst1. The combination of two transgenic approaches, one to induce early flowering and a second for the induction of sterility, allowed evaluation of this sterility strategy two years after transformation. This is a very short period of time considering the long vegetative period of seven to twenty years common in forest tree species. This approach opens opportunities for the assessment of sterility mechanisms for this plant group.