Seeds seem so simple. They’re small, sometimes so small that hundreds can fit into the palm of your hand. They’re containers for future life. Plant a seed, and you grow a new plant. But seeds are also fraught with controversy, and in the winter time, as gardeners everywhere pore over seed catalogues, it’s easy for confusion to reign in the mind of the new gardener. Hybrid, open-pollinated, genetically modified: when it comes to seeds, what does it all mean?
Seed Science: The Reason for a Seed
Let’s back up a step: what is a seed, and how does it work in ecology? The role of a seed is to create more plants. Seeds are also designed to move around to new areas, whether this is through the air or on an animal’s fur. Like any new generation of plants or animals, seeds house the future genetic diversity of a plant population. Plants that cross-pollinate will produce seeds that have the diverse characteristics of the parent plants. Just like children might have characteristics that reflect the characteristics of their parents, so too will plant seeds.
Genetic Modification: What Are Hybrid Seeds?
In the gardening world, humans have tinkered with the natural spread of genetic diversity, and this is where things get a little bit more complicated. Long before humans began to change the genetics of seeds with modern genetic modification, they meddled with the characteristics of seeds through a hybridization process.
Unlike genetically-modified plants, which can have genes of one species mixed with the genes of another, hybrid seeds come from the same sorts of plants. For example, a seed company might breed a tomato that had excellent blight resistance. That’s a desirable characteristic, since tomatoes are prone to all sorts of diseases.
Through repeated pollination of tomatoes with this desirable characteristic, growers would create an inbred parent tomato with exceptional blight resistance. Then, they might breed this tomato with another inbred line that has large fruit, producing hybrid seeds that will have large fruit and blight resistance.
Ultimately, these make hybrid or first generation (F1) seeds that breed true to the parents’ characteristics. Gardeners looking for specific characteristics such as size, color, or resistance to a specific disease may choose hybrid seeds. Since the seeds are bred under very specific conditions from inbred parent plants, gardeners have to buy these hybrid seeds every year to ensure that they get tomatoes with the characteristics that they would like to see, since future generations of the hybrid seed will not necessarily breed true.
Heterosis: The Mystery of Hybrid Vigor
Hybrid seeds are often more vigorous than the plants before them, a phenomenon called heterosis or hybrid vigor. This phenomenon is poorly understood, but it may be that breeding for very specific characteristics means that the hybrid plants lose some of their less-helpful recessive characteristics that inhibit growth. Another theory posits that crossing two inbred lines of plants can result in a mixture of genes that leads to greater growth ability.
Why Are Open Pollinated Seeds Best for Seed Saving?
Many gardeners look to open pollinated seeds if they’re thinking of seed saving. These seeds may also be labelled as heirloom seeds. Open pollinated seeds are different from hybrid seeds in that they are not crossed from inbred parent lines. This means that they may not have the specific characteristics of the hybrid seeds, but they are good for seed saving. Saving seed from an open-pollinated plant will yield new plants that are similar to the parents.
Decoding Science. One article at a time.