Full Length Research Paper

Optimization of regeneration and transformation parameters in tomato and improvement of its salinity and drought tolerance

Habib Khoudi^*, Aida Nouri-Khemakhem, Sandra Gouiaa and Khaled Masmoudi

Plant Molecular Genetics Laboratory, Centre of Biotechnology of Sfax (CBS), B.P”1117”, 3038 Sfax, Tunisia.

*Corresponding author. E-mail: habib.khoudi@cbs.rnrt.tn. Tel.: +216 74 871816

ext 1046. Fax: +216 74 875 818.  

Accepted 10 March, 2009

   Abstract

As part of our efforts to improve tomato tolerance to abiotic stress, we have undertaken this study to introduce two candidate genes encoding: a sodium antiporter and a vacuolar pyrophosphatase, previously shown to enhance drought and salt tolerance in transgenic Arabidopsis plants. First, we evaluated the potential of primary leaves from three to four week-old in vitro-grown tomato seedlings as alternative explants to cotyledons for tomato transformation. Our results demonstrated that primary leaves are three times more efficient then cotyledons in terms of regeneration percentage, productivity, and transformation frequencies independently of the medium and genetic construct used. Second, primary leaves were used to introduce the genes of interest using Agrobacterium-mediated transformation. Many transgenic tomato plants were easily recovered. The presence of the transgenes and their expression were confirmed by PCR and RT-PCR analysis. The transformation frequencies for primary leaf explants ranged from 4 to 10% depending on the genetic construct used. The time required from inoculation of primary leaves with Agrobacterium cells to transfer of transgenic tomato plants to soil was only 2 months compared to 3 to 4 months using standard tomato transformation protocols. The transgenic tomato plants obtained in the current study were more tolerant to salinity and drought stress than their wild-type counterparts.

Key words: Agrobacterium-mediated transformation, cotyledon, primary leaf, Regeneration, tomato.