MOLECULAR-GENETICS OF GROWTH AND DEVELOPMENT IN POPULUS .3. A GENETIC-LINKAGE MAP OF A HYBRID POPLAR COMPOSED OF RFLP, STS, AND RAPD MARKERS

We have evaluated three DNA-based marker types for linkage map constru ction in Populus: RFLPs detected by Southern blot hybridization, STSs detected by a combination of PCR and RFLP analysis, and RAPDs. The map ping pedigree consists of three generations, with the F-1 produced by interspecific hybridization between a P. trichocarpa female and a P. d eltoides male. The F-2 generation was made by inbreeding to the maximu m degree permitted by the dioecious mating system of Populus, The appl icability of STSs and RAPDs outside the mapping pedigree has been inve stigated, showing that these PCR-based marker systems are well-suited to breeding designs involving interspecific hybridization. A Populus g enome map (343 markers) has been constructed from a combination of all three types. The length of the Populus genome is estimated to be 2400 -2800 cM.