PRELIMINARY RESULTS TO ESTABLISH AN ALTERNATIVE SELECTION SYSTEM FOR APPLE TRANSFORMATION

The Agrobacterium-mediated gene transfer is one of the most important ways to transfer genetic material directly into the plant genome. In the last years, the use of antibiotic resistance genes for selection of transgenic plants has increasingly been discussed controversially. Therefore, new alternative selection systems have to be de-veloped. Alternatively to kanamycin selection, two new protocols regarding the Agro-bacterium-mediated leaf disk transformation of apple have been evaluated. A positive selectable marker gene such as manA that encodes for phosphomannose isomerase and provides transformed cells with a metabolic advantage over non-transformed cells was tested. Mannose was examined for an effect on shoot growth and regenera-tion efficiency to be added to the selection media in transformation studies. The sec-ond strategy was based on the green fluorescent protein gene (GFP) as a highly sensi-tive, vital reporter gene system for screening of transgenic plants. The detection of GFP expression with an epifluorescence stereomicroscope confirmed the effectiveness of GFP as a reporter gene for transient expression studies in tobacco and apple leaves and for screening of putative transformants. Molecular characterization of the trans-formed apple plants is currently underway to determine gene copy number and ex-pression levels.