Garlic cloves, lily and gladioli bulbs, Jerusalem artichoke tubers and strawberry stolons are all examples of plants reproduced as clones.
Genetic diversity, cloning and sowing 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 while cloning is the result of asexual reproduction.
Cloning is not a new technique. The Incas of Peru cloned potatoes in the 1400s by taking the underground tubers they harvested and replanting them for the following season. Most of the potatoes we plant today are clones of a variety that was developed over 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 harvest red-skinned, white-fleshed potatoes that have good texture when boiled and turn dark brown when fried. Garlic cloves, lily and gladioli bulbs, Jerusalem artichoke tubers and strawberry stolons are all examples of plants reproduced as clones. Each selected plant part, be it a tuber, stolon or bulb, is capable of producing a new plant that is genetically identical to the original individual.
Seedlings are tiny plants that grow from seeds. Seedlings are not clones. With the exception of self-pollinating plants, such as peppers, most seeds are the result of combined genetics from two different parents. One parent’s genetics are carried in the pollen while the other half of the seed’s genetics are found in the flower ovary of another plant of the same species. During pollination, the pollen fertilizes the ovary and a new genetic set is produced in the form of a seed. The resulting seeds and seedlings are important because 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, both seedlings and clones play a vital role in the fruit selection process. A fruit breeder will take pollen from the flower of a tree that has certain promising characteristics and place that pollen on the stigma of a flower of another fruit tree of the same species with different promising characteristics. The hope is that the best characteristics of each tree combine into one of the seeds found in the apple. These seeds will be planted the following spring. In a seed orchard, hundreds or thousands of seeds can be planted in a year. For apples, it takes about seven or eight years to produce fruit. During this time, many seedlings will be eliminated due to poor winter hardiness or poor growth habit. The remaining seedlings will be judged on the quality of their fruit. Color, texture, flavor, storage capacity 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 varieties of apples during his entire breeding career (40 years), he is hugely successful.
This process of pollination and crossbreeding not only occurs with fruit trees, but is used to find new cultivars of all kinds of food and ornamental plants. Once a seedling with desirable traits has been identified, that seedling will be cloned via methods such as cuttings, budding and grafting or more sophisticated cloning methods 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. Named cultivars of plants, trees and shrubs that you buy at your local garden center are clones of a seedling known to have superior genetics.
Seedlings and clones play an important role in food production around the world. While the bananas exported from Latin America all come from a single clone, it is developments in the field crop and vegetable seed market that allow farmers to feed an ever-growing world population with nutritious food at high yield. Traditional methods of hand-crossing to produce seeds have evolved into molecular genetics, DNA tagging 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; firstname.lastname@example.org). Check our website (www.saskperennial.ca) or our Facebook page (www.facebook.com/saskperennial) for a list of upcoming gardening events