Conifer genetic engineering: transgenic Pinus radiata (D. Don) and Picea abies (Karst) plants are resistant to the herbicide Buster

A biolistic transformation procedure was applied to co-transform embryogenic tissue of Pinus radiata and Picea abies with two plasmid DNAs. The first vector contained the bar gene, specifying resistance to the herbicide glufosinate, under the control of the maize ubiquitin promoter. This plasmid also contained the Pinus radiata germin cDNA sequence, in either sense or antisense orientation, driven by the ubiquitin promoter. The second vector contained both the nptII gene under control of the CaMV 35S promoter for selection of transgenic tissue on geneticin and the uidA reporter gene under control of the double CaMV 35 promoter. Polymerase chain reaction analysis of selected geneticin-resistant tissue showed that the transformation rates for the co-bombarded plasmid were high in both Pinus radiata (75%) and Picea abies (86%). A combination of phenotypic analysis and Northern hybridisation demonstrated that a number of the transgenic lines expressed all four transgenes. Regenerated plantlets from Pinus radiata and Picea abies transgenic lines were spray-tested with commercial rates of Buster (glufosinate at 0.5, 1.0, 2.0 and 4.0 kg active ingredient per hectare). Transgenic plants survived and continued to grow with minor or no damage to their needles, whereas non-transgenic plants regenerated from the same cell lines died within 8 weeks of spraying. To our knowledge, this is the first report on genetically engineered herbicide resistance in conifers, and the results demonstrate that this trait is a feasible option for plantation forestry.