An efficient Agrobacterium-mediated transformation system for poplar

Poplar is a model system for the regeneration and genetic transformation of woody plants. To shorten the time required for studies of transgenic poplar, efforts have been made to optimize transformation methods that use Agrobacterium tumefaciens. In this study, an Agrobacterium infective suspension was treated at 4 °C for at least 10 h before infecting explants. By transforming the Populus hybrid clone "Nanlin895" (Populus deltoides×P. euramericana) with Agrobacterium harboring the PBI121:CarNAC6 binary vector, we showed that the transformation efficiency was improved significantly by multiple independent factors, including an Agrobacterium infective suspension with an OD600 of 0.7, an Agrobacterium infection for 120 min, an Agrobacterium infective suspension at a pH of 5.0, an acetosyringone concentration of 200 µM, a cocultivation at 28 °C, a cocultivation for 72 h and a sucrose concentration of 30 g/L in the cocultivation medium. We also showed that preculture of wounded leaf explants for two days increased the regeneration rate. The integration of the desired gene into transgenic poplars was detected using selective medium containing kanamycin, followed by southern blot analysis. The expression of the transgene in the transgenic lines was confirmed by northern blot analysis.

Evaluation of genetic diversity in Aegilops tauschii accessions using morphological and AFLP markers

Thirty two accessions of Aegilops tauschii were used to assess its genetic diversity by morphological and AFLP data and to evaluate relationship between morphological and AFLP markers. Thirty AFLP primer combinations led to the amplification of fragments ranging from 50 to 500 bp of which, 97 were polymorphic across the 32 accessions. Although both AFLP and morphological data classified accessions in two groups, one possessing subsp. tauschii accessions and the other contained all accessions of subsp. strangulata with some accessions from the subsp. tauschii. This may be explained by intermediate and hybrid forms between these two subspecies. Comparison of UPGMA dendrograms of morphological and AFLP markers using the cophenetic correlation indicated a non significant correlation (r = 0.37). Nevertheless, AFLP and selected morphological characters appear as useful and complementary techniques for evaluation of genetic diversity in subspecies of A. tauschii.