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Wednesday, May 31, 2023

Sustainable Agriculture: Seed Basics

For their size, it’s impressive how much confusion seeds cause. “Haven’t we been genetically engineering seeds for years?” “Don’t GMOs occur on their own in nature?” These are common questions people less familiar with plant science might ask. In order to understand the politics of seeds, it is imperative that everyone involved in the debate has a common understanding of basic seed biology. Otherwise, the debate rages without moving anywhere.

Debates about genetically engineered seeds, the intellectual property of such seeds and the socioeconomic impact on people who feed themselves from seeds they’ve sown is crucial. Informed debate on such topics is essential if we are to make informed decisions at the personal and policy levels.

In my own experience, many hot-tempered debates about the politics of seeds end in me realizing that the person I am conversing with lacks an understanding of the biology behind what we are supposedly arguing about. Thus, this column will be the first of a pair. This week, I will clarify the biology of seed breeding, and next week I will offer my arguments for regionally-based breeding programs as opposed to GMOs.

First, let’s clarify the difference between genetically engineered, hybrid, heirloom and open-pollinated varieties. Many people incorrectly posit that mankind has been genetically engineering plants for millennia. This statement has one foot in reality and the other in ignorance.

It is true that people have bred plants for thousands of years. The indigenous peoples of Mesoamerica and the Middle East exerted intentional selective pressures — purposely saving seeds from useful plants — in order to develop foods and materials that suited their needs. This is considered conventional breeding. People still do it today.

Conventional breeders work in labs and in garden plots as we speak, selecting the most suitable seeds to save. This process can be sped up through hybridization depending on the end product one is hoping to achieve.

Gregor Mendel, the father of modern genetics, gave us the Mendel square that helped us figure out what the probability of having a blue or brown-eyed baby was. Mendel was a pea fanatic, and he is credited with being one of the earliest European scientists to experiment with intentionally crossing pea plants to produce a desired offspring. This process is called hybridization.

Where traditional breeding and hybridization start to differ is in the behavior of their seed. Traditionally-bred varieties are bred to be stable and open-pollinated; or rather, their seed will grow out to resemble its parent plants. Hybrid plants, however, are bred for hybrid vigor; the first seed will produce exceptionally well the first time you plant it, but the favorable characteristics will begin to wane each generation thereafter.

Hybrid varieties were introduced to the U.S. markets in 1951, much to the delight of some plant breeders and home gardeners. Hybrid seeds, however, never replaced open-pollinated varieties completely, because they required gardeners and farmers to purchase new seeds each season. Many felt this was an unnecessary cost.

Many small growers continued planting and saving their favorite seeds, which we now call heirloom varieties. For a variety to be considered heirloom, it must have been cultivated before 1951, the birth year of commercial hybrids. The seeds inside the juicy heirloom tomatoes you see at the Farmers Market were developed in our grandparents’ youth.

As technology progressed throughout the second half of the century, hybridization became more sophisticated, and techniques for modifying the specific genome of a plant were developed. Genetic engineering deals with organisms at the DNA level. By looking at an organism’s genome, scientists have begun to replace, alter and add genetic information between species. These seeds are then patented as intellectual property by the companies that produce them, and they become commodities which can be bought by consumers and protected by patent laws.

Open-pollinated, heirloom varieties function at the scale of a population, whereas hybrids function at the scale of selected individuals within a population. Genetically engineered varieties function not at the population or individual scale, but at the level of a gene. These differences are crucial, and the terms should not be mistaken for each other.


For more biological clarifications on seeds, email ELLEN PEARSON at erpearson@ucdavis.edu.