Gardening Articles: Care :: Seeds & Propagation
Hybrid or Open Pollinated (page 2 of 6)
by Ben Watson
What Makes a Hybrid?
'Black Zucchini' is highly regarded open-pollinated variety
A "hybrid" vegetable seed results from the cross or mating between two different varieties or "parents" of the same plant species. In the broadest sense, nearly all vegetables are hybrids, the only exceptions being plants such as beans, peas, lettuce and tomatoes that cross-pollinate only with great difficulty.
But today, "hybrid" has a narrower, legal definition: To advertise and sell a vegetable variety as a hybrid (often designated "F1," the parents must be known and its pollination controlled. Significantly for home gardeners, hybrid seeds cost a little to a lot more, and the seeds hybrid plants produce will not come true to type.
The modern era of plant hybrids began around 1900 when biologists rediscovered Gregor Mendel's studies of pea genetics. In 1917, Dr. D. F. Jones at the Connecticut Agricultural Experiment Station in New Haven learned that he could take two very unpromising corn varieties, cross them and get offspring with very good traits but nothing like either parent. In addition, the plants were clearly more vigorous than usual, and they were strikingly uniform in the way they grew.
This ability to combine desirable traits such as disease resistance and earliness in different parent lines, and then, finally, to combine them, producing vigorous and uniform offspring, gave breeders a powerful tool to reshape all sorts of plants. By the 1930's, many hybrid sweet corn varieties were available. These new varieties were all high-yielding, and some packed enough pest resistance to make corn growing practical where it hadn't been before. Today, almost all sweet corn varieties offered by seed companies are hybrids, more than for any other vegetable.
Seed Saver's Dilemma
One problem that breeders faced was that the seed the new hybrids produced did not come true to type. Instead, the offspring of these very uniform hybrids showed the very diverse traits of the grandparents. So to get more seed, the breeders had to go back and repeat the original cross. When the mechanics of making the hybrid-producing cross was simple and the volume of seed produced was great, as with corn, this issue was not critical. But for crops that required slow and detailed handwork, such as tomatoes, breeders took another tack.
After creating a tomato hybrid with desirable traits, breeders would go back and "stabilize" them for several generations until the variety could reproduce itself true to type as any open-pollinated plant. This process gave us classic tomatoes such as 'Marglobe' (1935) and 'Rutgers' (1937). Initially products of hybridization, these varieties are now considered to be open-pollinated and are treated as such.
According to John Navazio, a Ph.D. and former plant breeder for Garden City Seeds, many modern OPs are in fact "true-breeding hybrids" such as the tomatoes mentioned above. A more recent example is the 'Peacevine' cherry tomato introduced several years ago by Alan Kapuler, research director of Seeds of Change. He started with the popular hybrid tomato, 'Sweet 100', then selected and stabilized it over several generations. More recently, he has continued to grow out and stabilize other true-breeding OP varieties from commercial hybrids, such as the new 'True Gold' sweet corn.