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What's the difference between hybrids and genetically modified (GM) vegetable varieties?

The term "hybrid," which you'll often see in seed catalogs, refers to a plant variety developed through a specific, controlled cross of two parent plants. Usually, the parents are naturally compatible varieties within the same species. This hybridization, or the crossing of compatible varieties, happens naturally in the wild; plant breeders basically just steer the process to control the outcome. In contrast, GM varieties (sometimes called "genetically modified organisms," or "GMOs") are a whole different animal, as we'll explain in a bit. First, some background on plant hybridization.

Humans have been cultivating new plant varieties since the beginning of agricultural development, but until fairly recently, the process required patience. Developing a non-hybrid, open-pollinated (OP) variety using classic plant-breeding methods takes six to 10 generations, says John Navazio, a plant breeder and senior scientist for the Organic Seed Alliance in Port Townsend, Wash. (Most heirloom varieties are open-pollinated.)

Modern hybridization speeds up that process considerably. Using a method of controlled crossing devised by Charles Darwin and Gregor Mendel in the mid-19th century, plant breeders can now produce seed that combines the desired traits of two pure parent lines in the first generation. This creates a new variety known as an "F1 hybrid." To create F1 seed, seed companies grow two parent lines in the field each year, designate the male and female parents, carry out pollination under controlled conditions - such as hand-pollination under row cover - and then harvest seed from the females. "Plant breeders like F1 seed because it's faster and easier than breeding new open-pollinated varieties," Navazio says. "You can cull the bad traits from the parents while stacking their good traits in the F1 offspring." For gardeners, hybrids sometimes provide advantages compared with OP varieties, such as better disease resistance. Big seed companies also like F1 hybrids because the process gives them proprietary ownership of each new variety. And because seed from F1 plants won't produce uniform offspring, gardeners must buy new seeds each year.

Unlike hybrids, which are developed in the field using natural, low-tech methods, GM varieties are created in a lab using highly complex technology, such as gene splicing. These high-tech GM varieties can include genes from several species - a phenomenon that almost never occurs in nature. "With GM varieties, genes are transferred from one kingdom to another, such as bacteria to plants," Navazio says. A corn variety developed by Monsanto, for instance, includes genetic material from the bacterium Bt (Bacillus thuringiensis), which kills European corn borers. So far, only commodity crops with GM traits - such as corn, soy, alfalfa and sugar beets - have been approved by the U.S. Department of Agriculture (USDA) for use, primarily in processed foods and animal feeds. The exception is GM sweet corn, which is now available at your grocery store. (For more on foods in your grocery store that contain GM ingredients, see How to Avoid Genetically Modified Food.)