RESUMEN
We describe a highly effi cient and reproducible Agrobacterium-mediated transformation protocol applicable to several varieties of tomato (Solanum lycopersicum, earlier known as Lycopersicum esculentum). Conditions such as co-cultivation period, bacterial concentration, concentration of benzyl amino purine (BAP), zeatin and indole acetic acid (IAA) were optimized. Co-cultivation of explants with a bacterial concentration of 108 cells/ml for three days on 2 mg/l BAP, followed by regeneration on a medium containing 1 mg/ml zeatin resulted in a transformation frequency of 41.4%. Transformation of tomato plants was confi rmed by Southern blot analysis and β-glucuronidase (GUS) assay. The protocol developed showed very high effi ciency of transformation for tomato varieties Pusa Ruby, Arka Vikas and Sioux. The optimized transformation procedure is simple, effi cient and does not require tobacco, Petunia, tomato suspension feeder layer or acetosyringone.