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Unformatted text preview: Molecular Breeding 3: 39–47, 1997. 39 c 1997 Kluwer Academic Publishers. Printed in Belgium. Production of ROL gene transformed plants of Rosa hybrida L. and characterization of their rooting ability Theo P.M. van der Salm , Caroline J.G. van der Toorn, Reinoud Bouwer, Charlotte H. H¨anisch ten Cate and Hans J.M. Dons Department of Developmental Biology, Centre for Plant Breeding and Reproduction Research (CPRO-DLO), P.O. Box 16, 6700 AA Wageningen, the Netherlands ( author for correspondence) Received 22 April 1996; accepted in revised form 21 August 1996 Key words: adventitious root formation, Agrobacterium tumefaciens , A. rhizogenes , rootstock, rose, transformation Abstract Transgenic plants of the rootstock Rosa hybrida L. cv. Moneyway were produced via a two-step procedure. First, kanamycin-resistant roots were generated on stem slices from micropropagated shoots, which were cocultivated with Agrobacterium tumefaciens containing the neomycin phosphotransferase II ( NPTII ) gene for conferring kanamycin resistance, together with individual ROL genes from A. rhizogenes . Root formation was quite efficient and up to two kanamycin-resistant roots per stem slice were produced. In the second step, these roots were used to regenerate transgenic plants via somatic embryogenesis. Although regeneration lasted up to 12 months, production of several transformants was successfully accomplished. Untransformed escapes were not found, indicating that the initial selection on kanamycin resistance was reliable. The presence of a combination of ROLA , B and C genes enhanced adventitious root formation on micropropagated shoots and explants of stems and leaves. It appears that the auxin sensitivity was increased to such a degree that cells were able to respond even to endogenous auxins present in shoots and leaves. Rooting experiments in greenhouse demonstrated that adventitious root formation on cuttings was improved threefold upon introduction of these ROL genes. It is concluded that a method was developed for the production of ROL gene transformed roses with improved rooting characteristics. Introduction Rose is one of the most important ornamental crops worldwide. To increase vigour and disease resistance, roses are often grafted on a rootstock. As part of a research programme to improve growth character- istics of rose, we aim at the production of genetically modified rose rootstocks with an improved root sys- tem. For this purpose the introduction of the root loci, the ROL genes from Agrobacterium rhizogenes was chosen. These genes are well-known for their pheno- typical effects in the hairy-root disease [3, 25]. Four genes ( ROLA , B , C and D ) are involved in the observed changes in root formation and root morphology ....
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