USE OF AGROBACTERIUM-RHIZOGENES TO CREATE CHIMERIC APPLE-TREES THROUGH GENETIC GRAFTING

We induced roots in apple by cutting and by layering stems inoculated with A. rhizogenes, thereby producing chimeric plants containing transformed roots and normal shoots. We show that mannopine, whose synthesis is encoded by the Ri T-DNA, is produced in the roots and translocated to the aerial parts. A. rhizogenes can thus be used to propagate recalcitrant apple genotypes, creating chimeric plants that contain the products of foreign genes in their aerial parts, without having foreign genes physically present in the fruit. Furthermore, a single gene from the Ri TL-DNA (ORF 12 or rolC) is sufficient to produce root induction in apple, suggesting that this gene could be permanently inserted into the genome of a rootstock to improve rooting.