Genetically engineered tomato plants. The petri dish contains cultures of Flavr Savr tomato plants; the first genetically engineered whole food. Each plantlet has been cultured from a single cell, grown on agarose medium. Flavr Savr tomatoes have a gene that allows the fruit to ripen on the vine without softening; so they are tastier, do not need ripening with ethylene gas, and are not damaged during shipping. Tomato softening occurs due to the enzyme polygalacturonase. Flavr Savr tomatoes contain an anti-sense gene that blocks the enzyme. This tomato entered American supermarkets in 1994 but was withdrawn from the marketplace by Monsanto (which bought Calgene in 1997). Research conducted at Calgene in California, USA.