Richard Bogren, Johnson, Charles E., Fontenot, Kathryn
News Release Distributed 04/23/15
BATON ROUGE, La. – Different types of vegetable seeds and the produce that comes from them can be confusing, LSU AgCenter horticulturists say.
Even people who aren’t avid gardeners wonder about the differences between heirloom open-pollinated, hybrid and genetically modified plants, said LSU AgCenter vegetable specialist Kiki Fontenot.
“This can lead to great confusion about the different types of vegetables available for home gardeners and commercial growers alike,” Fontenot said. “Despite personal beliefs about the safety of various modifications to vegetables, it is very important that we as consumers and gardeners understand the differences between various vegetable types.”
“Think of an heirloom vegetable as you would an antique piece of furniture or vehicle,” she said.
Neither the U.S. Department of Agriculture nor any other organization has developed an official definition for describing an heirloom crop in terms of years.
“Some will argue that the seeds must be saved and handed down generation to generation for 25 years while other claim 50 years,” Fontenot said.
Either way, heirloom vegetables are those that have been in production for many years and must be open pollinated. However, not all open-pollinated plants are heirlooms.
Open pollination occurs when pollen grains are transferred by insect or rain or some other “natural” manner from one plant to another or from one plant back onto itself in a process called self-pollination.
Open cross-pollinated vegetable plants include cucurbits, such as cucumber, squash, watermelon, pumpkin and gourds; brassicas, such as cabbage, Brussels sprouts, broccoli, turnip and mustard; corn, beets and carrots. Self-pollinated plants include tomatoes, beans, lettuce and peas.
A self-pollinated flower structure is one where the pollen usually covers the female parts. So when wind or insects become involved, the pollen almost 100 percent of the time pollinates the same flower, said AgCenter vegetable researcher Charlie Johnson.
Cross-pollinated flowers differ, with female parts separated from the male parts, allowing them to become pollinated by a number of different flowers from the same plant or from another plant, he said.
It’s important to note that a bean cannot pollinate a tomato or any other vegetable for that matter, Johnson said. In order for pollination to occur and make a reproducible seed, the plants must be very closely related – tomato with tomato, squash with squash, corn with corn – and not corn with squash or any other variations.
Hybrids are derived from cross pollination of two different plants. They are the result of controlled cross pollination or are cross-pollinated by human intervention. “In other words, a paint brush or cotton swab was used to transfer pollen from one flower to another,” Johnson said.
Plant breeders find a characteristic in one vegetable that they really like. It might be fruit shape, color, size or taste, Johnson said.
“They take pollen from the desired plant and place it onto other plants female flower parts,” he said. The seed saved from the fruit produced by the controlled cross-pollinated flower will produce a plant that will express characteristics from both the male and female plant.
Unlike naturally pollinated plants, commercial hybrids have been developed under controlled conditions to ensure an exact cross to produce the desirable traits. This same type of pollination can occur in nature but is unlikely to be as reliable season after season, Johnson said.
Hybrid seeds produce first-generation plants that are all the same – like twins.
“If you save the seed of a hybrid, you will be disappointed in the results next season because the next generation will not have the same set of characteristics as the original hybrid,” Fontenot said. “That’s why you need to purchase seed each year to continue to produce the quality crop you desire.”
GMO or GEO or Transgenic
Genetically modified or genetically engineered organisms are not developed through pollination. Rather, the genetic make-up of the plant has been altered by modern biotechnology. This means that a desired trait or gene from one organism can be inserted into another, Johnson said.
Scientists can map out a plant’s entire DNA, which is the genetic code or recipe of how it is made. They can identify a small portion of that recipe – think of this as an ingredient – remove that ingredient and add it to a recipe of another plant to make it more desirable, Fontenot said.
This doesn’t occur through cross pollination, which transfers many genes, but in a laboratory using special instruments. “Some scientists use ‘gene guns’ to literally shoot genetic material from one plant into cultured cells of another plant,” Johnson said. “Or they might use special bacteria that enter plant tissue through wounds and thus implant them with new genetic material.”
Heirloom, open-pollinated and hybrid vegetable seed can be found at hardware stores, plant nurseries, online seed catalogues and similar places.
“If a vegetable variety is genetically engineered, it will be labeled on the seed package or in the seed catalogue,” Fontenot said. “In order to purchase transgenic seed, you will sign a waiver indicating that you will not redistribute the seed, you will not save the seed, and you will not purposely try to cross pollinate the seed.”
This agreement is made between the grower and seed manufacturer to protect their investment in the technology used to create that seed.
All vegetable seed is non-GMO unless labeled, and you will know when purchasing it because of the waivers you’ll sign. “Chances are unless you’re a commercial vegetable producer, this seed will not be available to you,” Fontenot said.
Only two traditional vegetable crops are available in GMO form – squash and sweet corn. GMO squash varieties include Freedom II, Independence II, Liberator III, Freedom III and Destiny III. GMO sweet corn hybrids include Attribute, Obsession II and Passion II, she said.
Gardeners may choose which seeds they will purchase.
“We don’t promote nor discourage the use of GMO seed,” Fontenot said. “Rather, we want to educate all gardeners about the differences in available vegetable seeds.”