Shoot regeneration capacity from roots and transgenic hairy roots of tomato cultivars and wild related species

The organogenetic competence of roots and Agrobacterium rhizogenes-induced hairy roots of twelve Lycopersicon genotypes was investigated. Both roots a nd hairy roots of L. peruvianum, L. chilense, L. hirsutum and two L. peruvi anum-derived genotypes regenerated shoots after 2-4 weeks of incubation on zeatin-contained medium. Anatomical analysis showed that shoot regeneration in roots could be direct or indirect, depending on the genotype considered . Hairy roots showed considerable differences in their morphogenetic respon ses, when compared to the corresponding non-transgenic roots. The differenc es observed may reflect the influence of the introduced rol genes on hormon al metabolism/sensitivity. Hairy root-derived T0 plants had shortened inter nodes, wrinkled leaves and abundant root initiation, and most produced flow ers and fruits with viable seeds. The hairy root syndrome was detected earl y in germinating T1 seedlings as a strong reduction in the hypocotyl length . Our data point to the possibility of the use of A. rhizogenes, combined w ith regenerating Lycopersicon genotypes, in a very simple protocol, based o n genetic capacity instead of special procedures for regeneration, to produ ce transgenic tomato plants expressing rol genes, as well as, genes present in binary vectors. Furthermore, the regeneration differences observed in e ach Lycopersicon genotype and in transgenic materials expressing rol genes open the possibility for their use in the analysis of both the biochemical and the genetic background of organogenetic competence.