Fast and efficient genetic transformation of sugar beet by Agrobacterium rhizogenes

Genetic transformation of sugar beet is characterized by a low efficiency owing to the poor competence of its cells to both transformation and regeneration procedures (Wozniak, 1999). To circumvent the problems arising due to sugar beet’s recalcitrance, Agrobacterium rhizogenes-mediated transformation is an attractive alternative system to study transgene expression and effect on root traits such as pathogen and pest resistance, abiotic stress tolerance and water and/or nutrient uptake. By analogy to Agrobacterium tumefaciens, used in standard transformation techniques, A. rhizogenes transfers a T-DNA segment from its root-inducing (Ri) plasmid into the genome of infected plant cells. Upon expression of the root locus (rol) genes, auxin and cytokinin biosynthesis is modified in a manner that promotes rapid proliferation of adventitious roots emerging at the wounding site, called hairy roots. The phenotype of the transformed roots is similar in structure to that of the wild type roots but is characterized by a fast hormone-independent growth, a high lateral branching and a plagiotropic root development.