African Journal of Biotechnology Vol. 5 (20), pp. 1851-1857, 16 October 2006   

ISSN 1684–5315 © 2006 Academic Journals        

Full Length Research Paper

Rapid genetic transformation of sweetpotato (Ipomoea batatas (L.) Lam) via organogenesis

H. R. LUO^1,2, M. SANTA MARIA^1‡, J. BENAVIDES¹, D. P. ZHANG^1†, Y. Z. ZHANG² and M. GHISLAIN¹*

¹Applied Biotechnology Laboratory, International Potato Center, P.O. Box 1558, Lima 12, Peru.

²College of life sciences, Sichuan University, Chengdu 610064, China.

*Corresponding authors E-mail: m.ghislain@cgiar.org.  Phone: 51 1 349 6017 / Fax: 51 1 317 5326.

†Present address: USDA ARS, PSI, SPCL, 10300 Baltimore Avenue, BARC-W, Beltsville, MD 20705, USA. OR Horticultural Science Department Box 7609, North Carolina State University, Raleigh NC 27695, USA..

Accepted 8 September, 2006

An efficient and rapid Agrobacterium-mediated transformation method based on de novo (via callus) organogenesis has been developed from petioles with leaf for sweetpotato (Ipomoea batatas (L.) Lam). Stable transgenic sweetpotato plants cv. Jewel were obtained in six to ten weeks after infection with Agrobacterium tumefaciens hyper-virulent strain EHA105 harboring a binary vector pCIP45 bearing the nptII gene conferring resistance to kanamycin and a gene of interest. PCR and Southern analyses confirmed stable integration of both genes into the sweetpotato genome. The expression of the nptII gene was assessed by reverse-transcribed PCR and callus development in a high kanamycin medium. A two-step organogenesis regeneration using media containing 4-fluorophenoxyacetic acid (4-FA) and zeatin was used in two independent transformation experiments yielding 20% and 10% transformation efficiency, respectively. When using indolacetic acid (IAA) in regeneration media, the transformation efficiency dropped to 4.0%. It indicated an auxin to cytokinin treatment could improve the regeneration of transgenic calluses. This rapid organogenesis-based transformation strategy represents an important improvement over existing methods and will facilitate producing large-scale transgenic sweetpotato plants the genetic improvement of a crop that is reputed to be difficult to transform.

Key words: Agrobacterium-mediated transformation, EHA105, organogenesis, sweetpotato, transgenic plant.