March 13, 2003

Abstract from a paper by
Nick de Vetten1, Anne-Marie Wolters2, Krit Raemakers2, Ingrid van der Meer3, Renaldo ter Stege1, Els Heeres4, Paul Heeres4 & Richard Visser2
1. AVEBE, AVEBE-weg 1, 9607 PT Foxhol, The Netherlands.
2. Laboratory of Plant Breeding, Wageningen University, P.O. Box 386, 6700 AJ Wageningen, The Netherlands.
3. Plant Research International, P.O. Box 16, 6700 AJ Wageningen, The Netherlands.
4. Breeding Institute KARNA, Valtherblokken Zuid 40, 7876 TC Valthermond, The Netherlands.
Correspondence should be addressed to R Visser. e-mail: richard.visser@wur.nl
Published in Nature Biotechnology

It is generally thought that transformation of plant cells using Agrobacterium tumefaciens occurs at a very low frequency. Therefore, selection marker genes are used to identify the rare plants that have taken up foreign DNA. Genes encoding antibiotic and herbicide resistance are widely used for this purpose in plant transformation.

Over the past several years, consumer and environmental groups have expressed concern about the use of antibiotic- and herbicide-resistance genes from an ecological and food safety perspective. Although no scientific basis has been determined for these concerns, generating marker-free plants would certainly contribute to the public acceptance of transgenic crops. Several methods have been reported to create marker gene–free transformed plants, for example co-transformation, transposable elements, site-specific recombination, or intrachromosomal recombination.

Not only are most of  these systems time-consuming and inefficient, but they are also employed on the assumption that isolation of transformants without a selective marker gene is not feasible. Here we present a method that permits the identification of transgenic plants without the use of selectable markers. This strategy relies on the transformation of tissue explants or cells with a virulent A. tumefaciens strain and selection of transformed cells or shoots after PCR analysis. Incubation of potato explants with A. tumefaciens strain AGL0 resulted in transformed shoots at an efficiency of 1–5% of the harvested shoots, depending on the potato genotype used. Because this system does not require genetic segregation or site-specific DNA-deletion systems to remove marker genes, it may provide a reliable and efficient tool for generating transgenic plants for commercial use, especially in vegetatively propagated species like potato and cassava.

The complete paper is available on the website of Nature Biotechnology at http://www.nature.com/nbt/