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The Art and Science of Seeds

by Rebekah L. Fraser
Moving toward the future to reconnect with the past

Photo by Bob M. Montgomery Growing seeds is not as simple as it sounds, and the differences between growing seeds and growing food crops are great.

Since the dawn of agriculture, farmers have saved seeds and developed hybrids. Modern horticulturalists have different expectations for crops than our ancestors did, and today’s breeders utilize new technologies to develop hybrids. The use of certain technological advancements has caused some to question the ethics and healthfulness of hybridization. Regardless of the way seed development is viewed, there is no denying its prevalence in modern agriculture. Although their motives differ, the work of independent farm researchers, university professors, home growers and scientists at worldwide conglomerates revolves around developing new seeds.

Growing plants vs. growing seeds

Growing seeds is not as simple as it sounds, and the differences between growing seeds and growing food crops are great. Fruits, vegetables, flowers and trees can grow side by side in a field. Seed crops must be separated by a few feet to over 3 miles, depending on the seed type, to prevent unintentional cross-pollination. The growing season for most annual vegetable crops is generally three to four months. However, to grow viable seed, a farmer must allow the plant to go through its entire life cycle, exposing the seed to a new range of diseases, pests and weeds. The nutrient profile, the latitude and the weather conditions needed for seeds also differ from the nutrients, day length and climate required to grow a food crop from that same plant.

For example, the Northeast region, with its high moisture content and cool fall temperatures, is ideal for growing lettuce as a food crop. The opposite conditions are necessary to grow lettuce seed. Therefore, seed developers and growers who want to offer multiple types of seed find it necessary to work with growers in other parts of the country suited for different types of seed.

Varieties of many food species, such as tree fruits and tubers, only grow from seed once. After that, the growing process varies. For example, apple breeders grow new plants from seeds initially, but once they have identified the tree they want, they utilize an asexual propagation method, such as grafting. Whether the fruit is a ground cover, a bush or a tree fruit, the seeds stimulate the growth of the fruit. Apple seeds can also be used to grow rootstock. However, producers are increasingly relying on clonally propagated rootstocks. Most fruits grown professionally in the United States are not propagated from seeds, but are grafted or propagated from stem cuttings.

Why develop hybrids and other new varieties?

Like most businesses today, agriculture has become increasingly market-driven. Although scientists espouse different reasons for selecting strains and developing hybrids, the common theme is that new plant varieties please consumers. Growers are looking for plants with increased disease resistance, weed resistance and pest resistance so yields are higher and labor costs are lower. Market consumers are looking for something different, something tasty and something reasonably priced—sometimes, they’re looking for something healthy, too.

“The purpose is to find a potato type that’s better than what you already have,” says Verlin Rockey of Milk Ranch in Colorado. He works mostly independently, but also collaborates with Dr. David Holm of Colorado State University. Along with his nephews (owners of Rockey Farms), Rockey introduces new varieties to the marketplace. Rockey Farms was part of the initial Yukon Gold push onto the fresh market, and they introduced fingerling potatoes to the U.S. market.

“If it’s not better than what you have, there’s no point in continuing on,” he says.

Rockey defines “better” as a potato that is great-tasting without seasoning and meets the standards of grower-consumers who need potatoes with resistance to disease, insects and pathogens. His Adora potato has a carbohydrate content that is 25 percent less than other potatoes.

Steve Peters of Seeds of Change says the variety of projects in breeding ranges from bringing two wild populations together to get new combinations, to selecting out of self-pollinating seeds.

Tom Stearns, founder and president of High Mowing Seeds in Wolcott, Vt., says there are numerous reasons to breed both hybrids and new open-pollinated varieties. First is the changing market conditions and environment. Diseases that used to be only in the South are moving to the North. Stearns says most growers expect the seed company to be ahead of changing conditions.

According to Stearns, consolidation in the global seed industry presents another reason for his company to breed new varieties. “When a bigger seed company buys a smaller seed company, they can no longer financially justify certain niche markets that the smaller company used to pursue. The economies of scale are not there, now that it’s a bigger fish.”

Stearns also says farmers using varieties developed for a different region, or for their region 30 years ago, face unnecessary challenges. They become less competitive, and it begins a downward spiral of marketing for that region. Many organic farmers do not have the best tools to match up with what they’re trying to do, and Stearns knows of few formal programs globally that are breeding for organic farmers. He feels it is important to focus exclusively on developing organic seeds.

At the University of Idaho, Dr. Mike Thornton is looking at manipulating potato seed physiology to provide optimum stem numbers so producers can meet market requirements for tuber size. Mark J. Pavek, Ph.D., is a potato and vegetable extension and research specialist at Washington State University’s department of horticulture and landscape architecture. Pavek is developing new potato and onion cultivars to produce similar or higher potato and onion yields with more human health benefits while using less water, pesticides, fertilizer and land to grow them.

Are hybrids inherently problematic?

One argument against hybridization is that the process weakens the plant and, in the case of food crops, the nutritional content. Jim Luby, researcher and professor of viticulture, fruit production and plant breeding at the University of Minnesota, says this is not a concern, especially for fruits. “Clonal propagation, whether by grafting or cutting, is probably a very old form of propagation.” Luby explains that most fruit plants don’t come from true seed, but are heterozygous. In addition, many fruits are not self-compatible and have a genetically enforced system of outcrossing. In this case, the hybrid has two parents: the egg is collected from the mother plant, and pollen to form the seed is collected from a different father plant. Two seeds from the same apple, even with the same mother and father, will not be genetically identical.

Another argument against hybridization is that farmers cannot save the seeds of the hybrids, and must buy new seeds every year. This may be true for genetically engineered seeds, but seeds developed via cross-pollination will likely be viable.

According to Luby, seeds saved from hybrid plants will not produce an exact copy of the plant they came from. As Stearns explains, hybrid seeds are actually an unfinished variety of an open-pollinated plant. Every time a seed developer makes a hybrid, they need to separately maintain parent A, parent B and the offspring to continue to create the hybrid seed. This instability is what sends growers to purchase more hybrid seed rather than risk growing a crop that they can’t sell.

Many species do not benefit from hybridization. Wheat, lettuce, peas and beans are examples of plants that are open- pollinated.

Should growers return to heirlooms instead of buying hybrids and other new varieties?

As Peters points out, varieties evolve over time. Since the heirloom boom in the United States is mainly the result of home gardeners saving seeds, there’s no guarantee the seeds were saved properly. Improperly saved seeds may have been growing too close to another variety and contaminated by unintentional cross-pollination. While some heirlooms are stronger and more disease, pest and weed-resistant than new varieties, this is not universal for all heirloom seeds. Heirlooms may have been weakened if not enough seed was saved to gather all of the necessary genetic material.

Peters says one needs seeds from at least 50 plants to get a proper genetic representation. “You really have to have knowledge of reproductive biology. We encourage seed saving, but there is a little more to it,” he explains. “Once a plant starts bottlenecking, you might end up with plants that have really weak tops or are distorted in some way. It could manifest itself in many different ways. You might be obsessed with eliminating green shoulders on carrots, and save seeds only from the ones with orange shoulders, but you haven’t saved enough, you might have carrots with nice shoulders but some other defect. You have to know the basics of biology.”

Heirloom potato varieties originated in the Andes, and Rockey says the varieties that have survived the centuries have the most virus and disease resistance. At Milk Ranch, Rockey and Holm have included about 30 heirloom varieties approximately 120 total varieties in their breeding system to pick up their disease and virus resistance. Rockey won’t propagate heirlooms as-is because they are deep eyed and rough. Via the crossing process, he “cleans” the heirlooms and makes them “user- friendly.”

Stearns works with heirloom varieties because he wants his customers to have choices. “There’s a desire in the market for a broad range of diversity in specialty produce. We find that diversity both in heirloom varieties that we rediscover, improve and produce, and also in developing new varieties that have combinations of traits that haven’t really been combined before.”

However, Stearns says many heirloom vegetables suffer from disease problems, which may be why they’re less known. Stearns says these heirlooms cannot be produced on a large scale without development, so researchers at High Mowing Seeds work to improve such varieties. The result is heirlooms strong enough for commercial growing and with the unique flavor, or color or shape that someone might associate with an heirloom variety.

Seeds of Change is also developing new varieties to meet the continual changes in the environment and the world. “We like to call [them] heirlooms of tomorrow. We’re not a museum, frozen in time,” says Peters. “Each generation you grow is slightly different than the last time.”

How new varieties are developed

The process of developing seeds differs depending on species. There are two ways to develop new varieties of open-pollinated seeds. For 10,000 years, farmers worldwide have altered the gene pool of certain plant species by selecting individual plants with desirable characteristics. Over generations, the gene pool narrowed enough to become distinct from the original variety. This basic method preserves the integrity of the species because nothing is added to the gene pool. However, it is possible to over-select and end up with a weaker variety than the original. Throughout this process, the seeds remain open pollinators.

The more modern method of developing new varieties of open-pollinated seeds is to cross two open-pollinated varieties, thus combining their characteristics, creating a new gene pool, and selecting from that cross the individual plants that have the desired traits. The initial result is a hybrid, and each year that seeds are selected and planted, a higher percentage of the plants will have the desired traits. After approximately seven generations, the desired traits will be present in all of the offspring plants. At this point, the new variety is a stable open-pollinated variety. Growers can save and plant seeds from this new variety with assurance that each subsequent crop will be the same.

Photo by Brian Prechtel. J.J. Haapala, an organic seed grower and director of research and education for Oregon Tilth, pours harvested Red Russian kale into a device that separates the seed from debris.

At the University of Minnesota, Luby evaluates cultivated and wild germplasm for traits that potentially enhance the value of fruit crops for consumers and producers. In his search for traits like good crispness in apples or early acclimation in the fall in grapes, he maps the corresponding loci on the chromosome he’s examining. “We’re not trying to reproduce the whole genetic fingerprint that we produce by grafting or cloning it. We’re trying to reproduce certain loci with certain traits that we want.”

These loci are molecular markers necessary in marker-assisted breeding. “In theory, we would aim towards building our own seed with texture from one parent, disease resistance from another and select from the offspring that have both, based on their DNA at certain loci.”

Luby explains that he doesn’t examine the whole genome of each parent because he hopes to discover or create some novel traits, too. “We may have an apple that’s red with good texture, but not resistant to a disease. Then, you have a different apple that’s ivory-colored, disease-resistant, but with a terrible texture. You may want to combine. We can do that without looking at the DNA, by simply growing out hundreds or thousands of seedlings. The idea is to increase our efficiency.”

Peters says he and the growers at Seeds of Change are still learning, even after almost 20 years in business. “The textbooks don’t have it all,” says Peters. “A lot of it is experience.”

The author is a freelance writer based in Massachusetts.