Stable transformation and tissue culture response in current European winter wheats (Triticum aestivum L.)

In order to efficiently complement traditional wheat breeding with genetic transformation technology it will be desirable to introduce transgenes into the ideal genetic background. Poor tissue culture performance is limiting the number of wheat genotypes that can be stably transformed. We statistically analysed the tissue culture response of 38 current European winter wheats and discuss genetic factors influencing this trait. Although regenerable callus cultures could be initiated from immature embryos of all 38 winter wheats analysed, the number of regenerated plants per cultured explant differed highly significantly (p<0.01) among genotypes. Ten cultivars with excellent ranking in this parameter were selected for transformation experiments. Independent transgenic plants were recovered from nine winter wheat genotypes with a frequency ranging between 0.2% and 2.0% of the cultured immature embryos after biolistic transfer of the bar gene and bialaphos selection. The nine transformable winter wheat genotypes included a recently released high-yielding, disease-resistant cultivar (cv. Certo), well established cultivars with elite bread-making quality (cv. Tarso, Alidos) and current breeding lines differing in yield, disease resistance and grain quality. Transgene integration and expression were confirmed by Southern blot analysis, polymerase chain reaction, phosphinothricin acetyltransferase activity assay and herbicide application. Transgene expression was stably transmitted to the sexual progeny of all transgenic lines analysed and segregated in a Mendelian fashion in the majority of lines. The introduction of transgenes into the ideal genetic background will allow a thorough evaluation of their crop improvement potential.