Most commercial varieties these days are hybrids. Many of the desirable traits are fixed for the plants that grow from that "F1" generation. But if you try to plant harvested seeds from those plants ("F2" generation) you'll get inconsistent results. It's possible to isolate particular traits via selfing and selecting for those traits. It's a years-long process, but I could see that happening in countries not beholden to Monsanto or trade deals.