The Impact of Chimeras and Bud Sports

In Horticulture


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” (, Lineberger, Professor of Horticulture, Texas A&M). Perhaps the best known chimera is the variegated Chlorophytum variegatum (Hessayon, 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., Ghent University, Belgium).


            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 Eurasia, it was “Johnny Appleseed - aka - John Chapman (Ibid) that was responsible for establishing the popularity of the apple in America. From the seedlings that emerged, selections were made for superior hardiness, fruit production, and disease resistance, and grafted onto seedling rootstocks. Sometimes superior branches derived from mutations in the bud, or bud sports, were isolated and gave rise to important cultivars as is the famous case with the ‘Red Delicious’. The ‘Golden Delicious’ arose as a chance seedling tree as did the popular modern cultivar ‘Braeburn’. All modern apple cultivars are highly heterozygous, providing ample opportunity for continuous variation in the development of new cultivars (


            Citrus producers, both grapefruit and orange growers have benefitted from genetic variations. To put the importance of these two fruits into proper perspective, the United States is the undisputed leader in commercial grapefruit production, accounting for 63 percent of the world supply, with the vast majority of it grown in Florida, at an economic value of about $122 million. Anyone over the age of 50 can remember the annoying number of seeds found in a typical green fleshed grapefruit, almost making them a nuisance to eat in spite of their nutritional value. Today, several seedless (or nearly so) cultivars exist that have originated from bud sports or chimeras, with the ‘Ruby’ series being the most popular. The navel orange is a bud sport that has provided millions in income to California growers during the winter months, and is relished by those of us in the “frozen north” during the long, snow-covered months that mark our winters.


            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,, 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?