Thanks for your question, Joanne! I'm a squash breeder who is responsible for developing new hybrids of both GM and non-GM zucchini, and I've had 14 years of experience in observing both, side by side, and in many growing environments. In all those years of observations, I've never found any trait that differentiates the GM and non-GM products. They look and grow exactly the same, except for when it comes to their reaction to infection by viruses.
There are many different types of squash, and they come in a wide range of colors, shapes, sizes and have a really wide range of uses. In every case the GM and non GM versions have no observable differences under normal circumstances. When the susceptible, non-GM squash plants are infected with one of the viruses (cucumber mosaic virus, zucchini yellow mosaic virus or watermelon mosaic virus), they quickly become very sick, and often die, but the GM virus-resistant versions have few or no detectable symptoms.
We insist on the legally binding agreement from farmers before sale of GM seeds to protect the farmer and ourselves, to be sure that they fully understand the laws about where their produce can be sold (USA and Canada). At the moment (until the end of the patent lifespan for the existing GM products, or until a competitor develops and achieves deregulation of a new transgene) ours is the only GM squash on the market.
Here at Seminis/Monsanto Vegetable Seeds, we only sell green zucchini, yellow straightneck and yellow crookneck squash in GM hybrid versions, so all of the other types of both hybrid and open pollinated squash should be GMO-free in all cases. We also sell non-GM squash hybrids and open pollinated varieties ofmany other types.