SPEAKER: All right. Let's talk a little bit about classical plant breeding. In the early 1900s, the work of Gregor Mendel was rediscovered. Mendel came up with the concept of genes as physical units of heredity and showed that, in fact, traits in most plants-- in fact, in all plants-- were controlled by these physical units that he called genes.
Using the concept of genetics, plant breeders developed a series of crosses, crosses to produce recombinant genes and to select for those recombinants for new and improved varieties. To make a cross, the process is really very simple. As this graphic shows, you basically remove the male flower parts, collect the pollen, apply the pollen onto the stigmas. The pollen tubes grow down, fertilize the egg cells, and produce seed, hybrid seed. The hybrid seed is then collected, planted, and then you look at what the progeny growing from those hybrid seeds look like.
You plant the seeds and then look at the first generation offspring, and variability among the plants in the first generation offspring is due primarily by differences in the genetic makeup of those individual plants. Environment can have an impact. But if you grow those plants over very uniform environment, you can actually see the genetic differences as inherited after the cross has been made.
Classical breeders use this technology and develop some very, very successful plant varieties. An amazing story of success is that of hybrid corn. For years, starting in the 1800s, hybrid corn yields in the United States did not change. During the 1930s, the first double-crossed corn hybrids were produced. And as you can see from this slide, the yields of hybrid corn began to increase linearly right on up to the present time.
After about 30 years of working with double-cross hybrids, breeders were able to produce single-cross hybrids around the 1960s. And you can see this rate of increase went up even faster. So this hybrid corn developed initially in 1930s. And by the 1950s, about 90% of the corn in Iowa and about 70% of the corn in the United States was hybrid. So the hybrid corn was adapted very, very rapidly.
Starting in the 1960s, a number of international agencies supported work aimed at improving crop yields to help feed a hungry world. This research resulted in what has been called a Green Revolution. The Green Revolution specifically refers to improved yield and productivity of wheat using new varieties developed by the International Center for Maize and Wheat Improvement in Mexico and rice utilizing varieties developed by the International Rice Research Institute in the Philippines.
The yields of both wheat and rice increased over 500% during the '60s and '70s and led to an increased production of food needed to feed large portions of Asia. The success of traditional classical plant breeding is very easy to see. If you look at the evolution of crop yields in the US over the last 70 years, you can see that the yields of all of our major crops, including sorghum, corn, peanut, wheat, rice, barley, cotton, potatoes, beans, and soybeans, have all increased at a linear fashion.
Right, you've seen tremendous success that classical plant breeding has had over the last several hundred years. About 20 years ago, new technology was developed using molecular biology tools. These tools have had a tremendous impact on traditional plant breeding. Next, we'll talk about the impact that molecular biology has had on plant breeding.
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Plant Breeding: Then and Now provides an overview of plant breeding techniques, from early crop domestication to the latest developments in biotechnology methods. Plant breeding is one of the oldest scientific disciplines that has developed over thousands of years. Discover how recent developments in biotechnology are changing the science and methods of plant breeding.
This video is part 2 of 6 in the Plant Breeding: Then and Now series.