Agrobacterium-mediated transformation of three economically important potato cultivars using sliced internodal explants: an efficient protocol of transformation

gosity greatly reduce the efficiency of traditional methods for potato breeding. Therefore, an alternative approach An efficient protocol has been developed for for further improvement of commercial potato varieties Agrobacterium-mediated transformation of internodal uses in vitro techniques, including somatic hybridization, explants derived from three economically important mutagenesis and genetic transformation. Several protoSolanum tuberosum genotypes, namely Bintje, Désirée cols for genetic transformation using leaf discs and potato and Kaptah Vandel. By combining the best treatments, tuber discs have been successfully employed to generate this protocol yielded an average transformation rate transgenic plants resistant to herbicides, insects and disof 90% of treated longitudinal cut internodal explants. eases (De Block, 1988; Imai et al., 1993; Benchekroun Seven to nine shoots per explant were obtained. The et al., 1995). However, all these procedures have major importance of zeatin riboside (0.8 mg−1 l−1) in the limitations, such as low frequency of transformation and, culture media, in controlling the development of highly more importantly, the occurrence of somaclonal variation organogenic micro-calli has been demonstrated. A at very high rates (mainly due to changes in the ploidy total of 450 morphologically normal transgenic plants levels) resulting from either prolonged or harsh tissue were regenerated. Stable integration and expression culture (Ooms et al., 1987; Ishida et al., 1989), thus of the transgenes were confirmed by histochemical limiting the production of transgenic plants for commerand molecular analyses. Short duration (7–8 weeks), cial applications. high efficiency, genotype independence and low freTwo varieties often used for in vitro culture are Désirée quency of somaclonal variation make this system well and Bintje. Désirée is the most frequently used in transsuited for wider commercial applications of transgenic formation experiments, in spite of its relatively low compotato plants. mercial importance, because it is very responsive in vitro. Due to its taste and cooking quality, Bintje is an important