Let’s be careful about knee-jerk reactions and assumptions regarding genetic engineering. This is not GURT (Gene Use Restriction Technology) or “terminator technology” that Monsanto has patented and proposed to use with some of their Round-Up ready crops (amid public outcry, they decided to drop the idea in 1999. By the way, the technology that they used and patented to produce GURT is a clever combination of conventional molecular biology techniques, if anyone is interested in further information).
Burpees is just using good old conventional plant breeding:
To get a seedless variety you cross a female tetraploid parent line with a male diploid parent (it doesn’t work if the male (pollen) is tetraploid and the female (egg) is diploid). The resulting hybrid is a triploid. Triploids have three sets of chromosomes that cannot segregate evenly during meiosis, so you cannot get gametes, so no seeds or pollen. Flowers and fruits appear normal, but they are sterile, so no seeds. H. Kihara invented this technique back in 1939 and its how you get seedless watermelon. Sounds simple but there are several difficult technical challenges. Producing an inbred tetraploid line that looks and tastes good, to use as the female hybrid, is not trivial. You then need a good diploid line to donate pollen, do the crosses and to find the correct combination that will give you healthy plants and good looking and tasting fruit. Those are the basics.
There are other challenges to doing this that are out of my field and the breeders may be able to fill in the details. For instance, I assume that self pollination by the tetraploid line will result in fruit that is easy to spot in the field and different from the fruit that forms triploid seeds, so that you only collect fruit and seeds from the true triploid lines. The other issue is more puzzling to me. The triploid lines are male and female sterile, so you would need pollen from a fertile diploid (seedful) variety to be planted with the seedless varieties. How do you market this for the home gardener who only wants 1 or 2 seedless tomato plants, or do you put a warning on the package that states you must grow these with normal, “seedful” tomatoes, or has Burpee found some way around this?
Full Disclosure: I am a plant research scientist at a major university. All of my funding is from NIH.