Genetic diversity, cloning and seedlings are words that all have one thing in common: they are the result of reproduction. Sexual reproduction results in seedlings that increase the genetic diversity of a particular species whereas cloning is a result of asexual reproduction.
Cloning is not a new technique. The Inca people of Peru cloned potatoes in the 1400s by taking the underground tubers that they harvested and replanting them for the next season. Most of the potatoes that we plant today are clones of a variety that was developed sometime during the last century. The Oxford Dictionary of Botany defines a clone as “a group of genetically identical cells or individuals, derived from a common ancestor by asexual reproduction.” When you plant a Norland potato tuber, you know you will be harvesting red-skinned, white-fleshed potatoes that have a good texture when they are boiled and turn dark brown in color if they are deep fried. Garlic cloves, lily and gladiola bulbs, Jerusalem artichoke tubers and strawberry runners are all examples of plants that are reproduced as clones. Each selected plant part, whether it is a tuber, runner or bulb, is capable of producing a new plant that is genetically identical to the original individual.
Seedlings are tiny plants that are grown from seeds. Seedlings are not clones. With the exception of self-pollinated plants, like peppers, most seeds are a result of combined genetics from two different parents. One parent’s genetics are carried in the pollen while the other half of the genetics of the seed are found in the ovary of the flower of another plant of the same species. When pollination occurs, the pollen fertilizes the ovary and a new set of genetics are produced in the form of a seed. Seed, and the resulting seedlings, are important as they increase genetic diversity and allow plants to evolve and adapt to changing environmental conditions. Cloned plants have a limited ability to adapt to changing environments.
In fruit production, seedlings and clones both play a vital part in the fruit breeding process. A fruit breeder will take pollen from the flower of one tree that has certain promising characteristics and place that pollen on the stigma in a flower of another fruit tree of the same species with different promising characteristics. The hope is that the best characteristics of each tree will combine in one of the seeds found in the apple fruit. These seeds will be planted out the following spring. In a seedling orchard, hundreds or thousands of seeds may be planted out in one year. For apples, it takes approximately seven or eight years to produce fruit. During this time, many seedlings will be eliminated due to poor winter hardiness or growth habit. Seedlings that remain will be judged on their fruit quality. Color, texture, flavour, storability as well as variability will be some of the basic qualities that will be tested. Finding a new apple variety is a long and arduous process. It is estimated that if an apple breeder finds two or three good apple varieties during his or her entire breeding career (40 years), he or she has been extremely successful.
This pollination and cross breeding process not only happens with fruit trees but it is used in finding new cultivars of all sorts of food and ornamental plants. Once a seedling with desirable traits has been identified, that seedling will be cloned via methods such as plant cuttings, budding and grafting or more high-tech methods of cloning such as tissue culture. These clones are then studied at various locations under various environmental conditions to determine whether or not they are worthy of mass production. The named cultivars of plants, trees and shrubs that you purchase at your local garden centre are clones of a seedling that was deemed to have superior genetics.
Both seedlings and clones play a significant part in food production in the world. Whereas the bananas that are exported out of Latin America all come from a single clone, it is the evolving seed market of field crops and vegetables that enable farmers to feed an ever-growing global population with high yielding, nutritious food. Traditional methods of manual crossing to produce seeds have evolved into molecular genetics, DNA marking and gene recombination. Whether modern or traditional methods are used, plant breeding is a process that requires careful observation, organized record keeping and diligence.
This column is provided courtesy of the Saskatchewan Perennial Society (SPS; saskperennial@hotmail.com ). Check our website (www.saskperennial.ca) or Facebook page (www.facebook.com/saskperennial) for a list of upcoming gardening events
