There are certain things that genetic engineering can do with plants that simply can’t be achieved through traditional breeding. Like working in a gene that makes, say, corn, able to withstand a blast of glyphosate, the agriculture industry’s favorite herbicide. There are, however, other scenarios that old-school horticulture and biotechnology can both tackle, like encouraging the development of a certain color and its associated antioxidant—like purple, as is the case in this tomato vs. tomato showdown.
The rise in popularity of heirloom varieties has vastly expanded the color palette of the tomato selection at grocery stores and farmers markets. But despite all of the evocatively named “black” varieties—Paul Robeson, Black Krim, Black from Tula—true purple tomatoes, the regal color signaling a concentration of healthy anthocyanins, didn’t exist until recently.
The promise of a healthier, genetically engineered tomato got the biotech crowd excited a few years ago when scientists at the John Innes Center in England successfully inserted a snapdragon gene into solanum lycopersicum, a splice that resulted in truly purple fruit—from skin to seed. Now new research shows that the high concentration of the flavonoid increases the shelf life of the tomato too.
If you’ve come across a purple tomato at the farmers market in the past year, then you’ve met the GMO fruit’s similarly pigmented cousin, the Indigo Rose. The small, purple-and-red-mottled tomato, bred at Oregon State University, was commercially released in 2012.
Jim Meyers, a professor at OSU who was involved with developed Indigo Rose, acknowledges that the transgenic tomato has his variety beat in terms of anthocyanin, pointing out that the pigment “is more uniformly distributed throughout the fruit.” According to a document provided by the John Innes Center, the GE tomato contains more of the sought-after antioxidant than blueberries and black currants; black raspberries have a far higher concentration.
But in terms of staying power, the new research might not only apply to the GMO variety, but to any anthocyanin-rich tomato. Meyers hasn’t done a scientific study yet, but what’s been observed in test plots offers compelling evidence of a longer shelf life. “We discovered this by taking pictures of fruit on the ground in the field and coming back a month later to discover the purple fruit looked pretty much like the day we picked it but the normal fruit was mush,” he said via email.
Meyers does see some differences between how his tomato ripens (and eventually rots) and the genetically engineered purple variety. “We had not observed a delay in ripening that is also reported in the extended shelf life paper, although Indigo Rose is a rather late ripening variety,” he wrote. “I had always attributed this to being late maturing, but it could be that this is a side effect of anthocyanin in the fruit.”
And then there’s this to consider: Indigo Rose, Meyers points out, is commercially available. So as far as consumers are concerned, the only anthocyanin-rich, potentially long-lasting tomato out there is the Indigo Rose. Mark a point for traditional plant breeding.