The Impact of Chimeras and Bud Sports
Andrea L. Carlson
Houseplant and fruit loving Americans are basically unaware that some of the most appreciated plants and delicious fruits consumed in our country are from bud sports or chimeras. The terms are often used interchangeably, and to the average consumer, the differences are a moot subject. Botanically speaking, the chimera is where two or more distinctly different tissues are overlaying one another, while a sport is a part of a plant that shows unusual or singular deviation from the normal or parent plant; mutation (Random House College Dictionary, April 2001, 2nd revision).
Horticultural scientists go a little further in their
definition: “A plant is said to be a chimera when cells of more than one
genotype (genetic makeup) are found growing adjacent to tissues of that plant”
(aggie-horticulture.tamu.edu., Lineberger, Professor
of Horticulture, Texas A&M). Perhaps the best
known chimera is the variegated Chlorophytum
D.G. “The Houseplant Expert” 2002 Edition). Likewise, the more scientific
definition of a bud sport “is the consequence of sudden variations in gene
expression of somatic cells, leading to the phenotypically
altered shoots on plants” (South African Journal of Botany Abstracts 2002, 69:
117-128. S. De Schepper, et.a.,
These definitions aside, this paper will deal some of the more important bud sports and chimeras that have had a significant impact on horticulture.
Apples, oranges and grapefruit are among the most interesting and sports or chimeras to occur that have had profound economic impacts on the fruit production industry.
Apples, for example have been consumed by humans for over
2800 years (Growing Fruit in the Upper Midwest, Don Gordon, 1991, UMN,
pg. 22) and although being native to
Citrus producers, both grapefruit and orange growers have
benefitted from genetic variations. To put the
importance of these two fruits into proper perspective, the
The two fruits - the apple and the red-fleshed grapefruit have unique nutritional qualities about them. The whole apple is considered a low-glycemic index fruit which means that it is slow to elevate the glucose in the blood, making it an acceptable food source for diabetics. The red or ruby grapefruit is a rich source of lycopene and vitamin A, which are both important in maintaining good health (along with the generous amount of vitamin C they contain!) along with being good anti-cancerigenic agents (The Concise Encyclopedia of Foods & Nutrition, Ensminger, et.al., CRC Press, 1995, pg. 628).
From Chimeras and Bud Sports Come Clones:
Most of the horticulturally important plants arose from the periclinal chimera, which is a complete layer of mutated tissue within the plant, and are the most stable for dependable horticulture production (see sketches). The other two chimeras, the mericlinal and sectorial, are less stable and are therefore not as important in horticulture.
Clones are important in horticulture because:
1. They fix the genetic character of as a result, the phenotypic character of the plant.
2. This leads to completely uniform plant material, which can lead to pest and disease resistant forms of plants.
3. The productive character or desirable flower color of the of the clone is perpetuated to all the individuals originating from the parent plant.
4. Productivity is usually accelerated due to the by-passing of the juvenile phase
Disadvantages of clones should also be mentioned here. They are:
1. With any kind of monoculture insects and pathogens may evolve to find the new clone an ideal host, and could wipe out entire plantings literally overnight if close vigilance is not maintained.
2. Cloning is asexual reproduction, and as such, is more expensive than sexual or seed production.
3. There is the potential for genetic variation and environmental influence to change the phenotypic and genotypic character of the original discovery.
This just “tip of the iceberg” delving into the impacts of bud sports and chimeras have on horticulture production and income, brings to light the importance of continuing to work with mutations well into the future. Some will continue to occur naturally while scientists will continue to carry on research attempting to create mutants that can be used to the benefit of our over-crowed planet. Clearly, traditional sexual propagation research will be carried on for the potential it holds for the industry, but much of what we enjoy and take for granted these days has come from natural mutations.
Doesn’t this make Mother Nature a wonderful genetic engineer?