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Building better plants - Norman Borlaug and the Green Revolution

There are a lot of hungry mouths to feed in the world. How did modern agriculture come to support such a large population?

Feeding people has always been a problem. From early hunter-gatherers to modern day, people have always had the basic concern of getting enough to eat. The first great innovation was the domestication of crops approximately 10,000 years ago. Progress was slow in transforming wild species into the high producing varieties that we enjoy today. For a long time, crops were developed simply by replanting seeds from the best performing plants a farmer had in their field, without particular goals in mind besides having a successful harvest the following year. With the advent of modern breeding practices however, this process became a more refined science. Selecting plants with particular traits allowed for the development of crops that could tolerate specific problems - disease, drought, pests, etc. These conventional breeding practices were effective, but still required many generations of plants to find and maintain the best combination of traits.

Modern plant breeding programs really took off in the early 1900s, and one name is synonymous with these efforts: Dr. Norman Borlaug (Figure 1). Hired by the the International Maize and Wheat Improvement Center as a geneticist and plant pathologist in 1944, Borlaug began the work he would pursue the rest of his life - improving crops to better feed a growing global population. By 1964, he was the head of the International Wheat Breeding Program. Wheat is the third highest consumed cereal crop in the world, a staple across the developed and developing world alike. Unfortunately, wheat productivity has long been plagued by stem rust (Puccinia graminis), a fungus that afflicts cereal crops, drastically reducing yield. Borlaug and colleagues worked for decades using conventional breeding methods to develop lines with multiple resistances to stem rust, and eventually succeeded in making several highly resistant lines with excellent grain yields.

image alt text Figure 1. Norman Borlaug in his wheat breeding fields in Mexico, 1970.

Unfortunately, the genetic background of these high yielding, disease resistant cultivars also gave them long, thin, stems. The weight of the extra grain and the fast growth spurts caused by fertilizer applications often caused these lines to lodge, falling over and making the grain unusable. To remedy this, Borlaug collaborated with other scientists and obtained a dwarf variety of wheat developed in Japan. By crossing this dwarf wheat with his own cultivars, Borlaug created semi-dwarfed hybrids that could tolerate stem rust, produce large quantities of grain, and not fall over! This may sound like a trivial achievement at first - crops that won’t fall over - but the impact of these new lines was monumental. In the 1960’s, the Indian subcontinent was experiencing yet another famine in a long history of starvation and agricultural strife. Borlaug’s new wheat varieties were introduced to the region in 1962, and by 1970 wheat yields had nearly doubled throughout the region. By the mid 1970’s, both India and Pakistan could sustain their populace on domestic grain production. This agricultural boom was heralded as the Green Revolution, and Norman Borlaug was its founding father. His breeding efforts are credited with saving over 1 billion people from starvation, and in 1970 he was awarded the Nobel Peace Prize for his efforts.

The success of Norman Borlaug and the Green Revolution in shaping global food security are a testament to the value of highly focused crop breeding programs. Today, even more detailed approaches have been made available to breeders with the advent of whole genome sequencing. Conventional breeding has been largely replaced by marker assisted breeding, where known genetic markers in a crop’s DNA can be closely associated with a desirable trait, such as drought tolerance or pest resistance. Breeders do not have to know the exact gene or genes responsible for the trait, but they can track it through multiple generations by following the markers associated with it. This approach streamlines the integration of new traits into existing cultivars by reducing the need to screen all the progeny of a hybrid plant for functional evidence of the trait - they can just follow the DNA markers and propagate the offspring that retain the desired traits inherited from the parental plants.

Beyond marker assisted breeding lies the contentious issue of genetically modified (GM) crops. This highly specific approach to plant modification relies on scientists knowing the function of a specific genetic element, and then modifying a plant’s genome to add, enhance, or reduce the effects of that element. This modified genetic element can be native to the plant (cisgenic) or from another species altogether (transgenic). The main advantage of this approach is that it allows crop scientists to draw from a much wider range of traits from across all domains of life to address a problem faced by the plant, rather than relying on the much smaller pool of traits existing in current varieties available for breeding. While some see this approach as a departure from “natural” crop development, Norman Borlaug himself recognized the potential genetically engineered crops to meet future food demands, saying:

“Genetic modification of crops is not some kind of witchcraft; rather, it is the progressive harnessing of the forces of nature to the benefit of feeding the human race. The genetic engineering of plants at the molecular level is just another step in humankind’s deepening scientific journey into living genomes. Genetic engineering is not a replacement of conventional breeding but rather a complementary research tool to identify desirable genes from remotely related taxonomic groups and transfer these genes more quickly and precisely into high-yield, high-quality crop varieties.”

Many concerns have been raised about implementing GM techniques and the effects they may have on human and environmental health. While some of these concerns are valid, pseudoscience and mis-information often clouds the understanding of the science behind GM crops, which will be addressed here in future posts. Feeding people may have always been a problem in the past, but hopefully with the continued efforts of plant breeders and crops scientists, one day it won’t be.

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