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Animal, Vegetable, Miracle - Vegetannual.jpgWhere Do New Plants Come From?

Well, new plant species arose (and still arise) through plant evolution, that is, as a consequence of hundreds of millions of years of natural selection.

About 12,000 years ago, however, humans got involved.

Early examples of humans trying to manage plants for their benefit likely included burning of forests to encourage herbaceous plants, the vegetative propagation of plants using tubers (think yams, e.g.), and, of course, the saving and sowing of seeds from “desirable” plants.

After people began domesticating plants, things got a bit more interesting. They began producing so-called “cultigens”, that is, plants that have been deliberately selected by humans, a.k.a., “artificial selection”.

1761o.jpg Thus, the field of plant breeding commenced. (An excellent book on this subject is Hybrid: The History and Science of Plant Breeding)

On the left is shown an Assyrian relief carving from 870 B.C. depicting the artificial pollination of date palms.

So, even though they didn’t know the scientific basis of plant breeding, humans were apparently actively engaged in it nearly 3,000 years ago.

Remarkably, this lack of understanding of the genetic basis of plant breeding was true even up to the early twentieth century, until, of course, the experimental results of Gregor Mendel were discovered and disseminated.

Besides the production of plant hybrids via cross pollination, new plants can also be made by the ancient art of grafting and the relatively new technique called transgenics, a.k.a., plant genetic engineering. (Since I’d like to focus on transgenics, I’ll refer you to an excellent introduction to grafting here.)

1977 – The Genie Emerges From The Bottle

Though humans have been making new plants for thousands of years, they’ve only been making transgenic plants for about 30 years.

Most agree that the era of plant genetic engineering began when a scientific paper was published in 1977 showing that a pathogenic bacterium by the name of Agrobacterium tumefaciens was able to insert some of its own genes directly into the genome of its plant hosts.

This research was conducted at the University of Washington (UW) in Seattle primarily by Dr. Mary-Dell Chilton, who was then a postdoc, working with Prof. Milton Gordon and Prof. Eugene Nester, in the departments of Biochemistry and Microbiology, respectively. (Among her honors, in 2002, Dr. Chilton was awarded Franklin Institute Award in Life Science, and, in 2008, was profiled in Scientific American.)

As a graduate student in the Botany Department at UW at the time, I remember attending a seminar by Dr. Chilton reporting this discovery. As I recall, the implications of this finding regarding the potential genetic transformation of plants was certainly recognized at the time. That is, that Agrobacterium could potentially be used as a means to deliver foreign DNA, i.e., a genetic vector, into plant cells, thus genetically altering them.

Remember that by 1977 scientists knew how to cut and paste genes (recombinant DNA) and regenerate whole plants starting with only a few plant cells using plant tissue culture. So the implications of this 1977 paper were enormous.

Fast-forward to 1983 –

Transgenic plants were first created in the early 1980s by four groups working independently at Washington University in St. Louis, Missouri, the Rijksuniversiteit in Ghent, Belgium, Monsanto Company in St. Louis, Missouri, and the University of Wisconsin. On the same day in January 1983, the first three groups announced at a conference in Miami, Florida, that they had inserted bacterial genes into plants. The fourth group announced at a conference in Los Angeles, California, in April 1983 that they had inserted a plant gene from one species into another species.” (from ref 2 below)

To be continued….

References
1. Three Ways to Make a New Plant, The Exploratorium, San Francisco, California.

2. Transgenic Crops: An Introduction and Resource Guide – History of Plant Breeding, Colorado State University.

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