Prospects for applications of rol genes for crop improvement

Prospects for the applications of rol genes for crop improvement are discussed. As suggested in many reports, rol genes are suitable tools to modify plant developmental processes, such as formation of adventitious roots and release of axillary buds from apical dominance. Practical applications, however, might be hampered by the many pleiotropic side effects that are observed in plants transformed with vol genes. Alternative approaches need to be developed, therefore, to overcome these undesired effects. We offer a novel approach for application that is clearly different from earlier strategies, and that is based on the application of rol genes in combination plants; i.e., plants consisting of an untransformed scion grafted on a rootstock transformed with a vol gene. Ln rose it was demonstrated for the first time that expression of rol genes in rootstocks led to an accelerated release of axillary buds of the untransformed scion, but without the transmission of many undesired pleiotropic effects. We expect that this stimulation will result in a changed plant architecture leading to a more efficient production of roses. Alternatively, the pleiotropic effects may be overcome by employing vol genes that are driven by organ- or tissue-specific promoters, leading to a more defined expression of these genes.