Genetic transformation of Populus tomentosa to improve salt tolerance

Soil salinity can be a limiting factor for productivity in agriculture and forestry. In order to fully utilize saline lands productively in plantation forestry for pulp production, the genetic modification of tree species for salt-tolerance may be required. The AhDREB1 gene, a DREB-like transcription factor gene, was transferred into Populus tomentosa by Agrobacterium-mediated transformation. Transgenic plants were regenerated and selected using a two-step process; first on Murashige and Skoog (MS) basal medium containing 4.44 mu M 6-benzyladenine (BA), 1.61 mu M alpha-naphthaleneacetic acid (NAA), 30 mg l(-1) kanamycin, and 250 mg l(-1) ceftomine, and then enhanced selection on medium with 50 mg l(-1) kanamycin. The putative transformants were confirmed by polymerase chain reaction (PCR) and Southern hybridization for the AhDREB1 gene. Transgenic plants were rooted on half-strength MS medium containing 5.71 mu M indole-3-acetic acid (IAA), 1.61 mu M NAA, 2 g l(-1) sucrose, and 5 g l(-1) agar. The salt tolerance of transgenic plants in pots in the greenhouse showed a survival rate of 100, 100, 84.4, and 44.4% after watering with a solution of 34.2, 68.4, 102.7, and 136.9 mM NaCl, respectively.