STIMULATION OF SCION BUD RELEASE BY ROL GENE TRANSFORMED ROOTSTOCKS OF ROSA-HYBRIDA L

For improvement of the root characteristics of roses, the rolA, B and C genes from Agrobacterium rhizogenes were introduced in the cultivar Moneyway, which is used as a rootstock. Four independent rolA + B + C transformants were produced. One rolC expressing transformant, showing good growth and clearly decreased apical dominance, was selected for a grafting experiment with the cut rose cultivar Madelon as a scion. G rafting on this rolA + B + C transformed rootstock resulted in a stimu lation of both root development of the rootstock and axillary bud rele ase of the untransformed scion. Axillary bud release increased from 0. 1 to 0.6 and from 0.3 to 1.3 basal shoots per plant at 15 degrees C an d 20 degrees C, respectively. Since basal shoots form flowers, this al tered plant architecture will presumably lead to a more efficient flow er production.