Use of Agrobacterium rhizogenes to create transgenic apple trees having an altered organogenic response to hormones.

The apple rootstock, M26, was genetically and phenotypically transformed using the Agrobacterium wild-type strain, A4. First, chimeric plants were obtained having transformed roots and normal aerial parts. Transformed plants were then produced through regeneration from transformed roots. Transformation was demonstrated by molecular hybridization and opine analysis. The effects of hormones on organogenesis was altered in transformants: cytokinins were required to form roots, whereas auxin was toxic at the concentration used to induce rooting in the control.