Dehybridization is a process aiming to stabilize a F1 variety, allowing its seeds to grow true. Depending on the variety and the environmental conditions, between 5 to 10-15 years are required to dehybridize a plant variety. Through careful selection and roguing, the variety gets closer and closer to the desired traits each year, giving the opportunity to create a new, stable open-pollinated version after several generations. However, the degree of successful stabilization may vary from one hybrid variety to another–especially with commercial F1s–and the process often requires growing a larger plant population than usual to ensure an effective selection, encourage genetic variety, and avoid inbreeding depression.
Seeds that are saved from a F1 hybrid (first generation) and replanted will result in a F2 hybrid (second generation), and so on. Starting with the second generation, the plant population will exhibit genetic instability–sometimes significantly–with most individuals having a different phenotype and being less vigorous than their parents. From there, seeds are saved based on the most desirable traits found within the population (resulting from a cross-pollination between the population’s individuals), used to grow the next generation, which in turn will go under another selection and roguing process. The genetics of the variety is deemed stabilized after several generations (seven selection cycles on average), when the sought phenotype is widely observable across the plant population and shows very few variations.
Should you come across a generation with a population that does not contain any plants with the desirable traits, replanting the previous generation can sometimes be necessary. During the dehybridization of a variety, some backcrossing (crossing with one of its parents) might indeed be required if you end up with several individuals showing different sought characteristics, which might help you faster stabilize the variety. Note that the more complex and varied you make the genetics, the longer it will take to dehybridize and stabilize a variety, which might require additional plant breeding knowledge.