From Seed to Seed:
The six-million-dollar plant?
A History of Plant Breeding
Now let's look at how the field of plant breeding evolved, and how it has been influenced by the advances in our understanding of the mechanics of heredity.
Some people have an image of plant breeders as scientists in lab coats "creating" new plants in their labs. This vision may be accurate in our current era of tissue culture and genetic engineering. However, for millennia plant "improvement" took place in the field, where farmers, observing that one corn plant produced larger ears than the others, saved seeds from a few ears for planting the next season. These represented the humble beginnings of the incredible and, in terms of feeding a growing population, vital science of plant breeding.
Plant breeding involves not only science, but art-often with a little luck thrown in. Think again of Mendel's scientific approach, patiently growing out generation after generation of plants, observing them with a critical eye, and keeping meticulous notes. Plant breeding also requires some degree of intuition in choosing which plants to cross among the almost endless varieties. Finally, throw in the attitude of an inventor, with the foresight to see the potential value in unintended results.
Ask your students to consider how they would choose to improve the plants that they are growing in the classroom or garden. Would they change the color of the food? The shape? The size? The taste? What kind of improvements might people who ship and sell fruits and vegetables be looking for? Emphasize that, rather than luscious, tender, good-tasting food, plant breeders are often focused on producing food that can travel long distances to reach its destination when it is perfectly ripe and undamaged.
Artificial selection. As soon as humans began selecting and saving particular seeds, they began the process of crop improvement. By carefully observing growing crops and choosing seeds from the best plants to save for the next season, farmers slowly improved production, taste, pest resistance, and/or other features of their crop plants. As opposed to the evolutionary process of natural selection, where the "fittest" survive and reproduce, this type of crop improvement allows farmers to encourage plant qualities that they consider important. Throughout much of the long history of agriculture, this was the only method of improving crop plants.
Hybridization. Once the fundamentals of plant reproduction were understood, the science of plant breeding began to emerge. Early plant breeders identified desirable characteristics, and carefully cross-pollinated plants in the hopes of bringing these characteristics together in one plant. This technique is slow and requires patience and precision. A cross-pollinated plant might produce hundreds of seeds, and each of these would be planted. The new seedlings would be nurtured to maturity and, once again, those with the most desirable traits would be selected. This process would continue until a suitable plant was found. The breeders would then begin the task of propagating the suitable plant to produce commercial quantities of seed.
Why do breeders go to all of this trouble?
Hybrid vigor. You may have heard the term hybrid vigor. We mentioned earlier that hybrid plants are often more uniform than non-hybrids. Also, hybrids sometimes exhibit dramatic improvements in yield, size, disease resistance, or other desirable features when compared with the parent plants. Scientists do not know exactly why this occurs, but suggest that it may be stimulated by the mixing of the very different gene pairs of the parent plants.
Breeders sometimes cross crop plants with some of their wild ancestors, hoping to impart the ancestor's desirable features, such as disease resistance or hardiness, without losing the current variety's palatability or yield. Considering that very few crossings actually result in progeny showing significant improvements over the parent plants, and how time-consuming and tedious the process is, the accomplishments of plant breeders are all the more remarkable.
Made possible by a grant from Oracle Corp.
Copyright 2001, National Gardening
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