Download Agriculture`s Sustainable Future: Breeding Better Crops

Special Editions - July 15, 2009 Scientific American
Agriculture's Sustainable Future: Breeding
Better Crops
Modern technologies can increase crop yields and reduce
agriculture's environmental impact
By Richard Hamilton
We are not going back to the pleistocene age of the hunter-gatherers. Instead experts indicate that
the world’s population will increase from approximately six billion to nine billion by 2050—all
to be fed, clothed and even fueled by agricultural products. What’s more, as people rise out of
poverty, higher living standards such as greater meat consumption and personal mobility will
place even more demand on food crop production (wheat, rice), animal feed (corn, soybeans),
fiber (wood, cotton) and fuels (sugarcane, switchgrass). How can agriculture’s output expand so
dramatically without significantly increasing its environmental footprint, especially reckless
deforestation to clear land for farming? Like contemplating office space in Manhattan, we must
find a way to grow vertically, by increasing crop yields.
Agriculture is not natural; it is a human invention. It is also the basis of modern civilization. Yet
agriculture is not uniform in its practices or productivity: some 40 percent of the world’s corn
farmers still use nonhybrid, open-pollinated varieties that the U.S. abandoned decades ago, and
their yields are far, far lower than what could be achieved with modern seed varieties. Nor is
agriculture static. Yield increases through improved genetics are accelerating in crops that
receive intense private research funding, such as corn, but are languishing in cassava and other
important staples for the developing world, which get little or no support. Agriculture has
significant ecological consequences, too: displaced forests and grasslands, greenhouse gas
emissions from fertilizers and diesel-fueled farm machinery, and algae blooms from excess
nutrient runoff. Clearly, there is much to improve on.
Modern humans emerged some 250,000 years ago, yet agriculture is a fairly recent invention,
only about 10,000 years old. Many crop plants are rather new additions to our diet; broccoli—a
flowering mutant of kale—is thought to be only 500 years old. Most innovation is far more
recent still. Although Austrian monk Gregor Mendel’s pea plant experiments quietly laid the
basic foundations of genetics in the mid-19th century, his work was rediscovered and applied to
crop breeding only at the beginning of the 20th century. Mendel demonstrated that plant traits
were inherited and not acquired from the environment, which meant that crossing two plants
with different characteristics could create a plant with potentially improved traits.
Further advances have steadily accumulated. The 1940s saw the identification of DNA as genetic
material and the adoption, by commercial breeders, of genetic modification—typically by
applying chemicals or radiation to DNA to try to make plants with advantageous characteristics.
The modifications ultimately led to the green revolution of the 1960s and 1970s, during which
time global wheat yields tripled. The 1980s and 1990s saw the commercial adoption of
agricultural biotechnology, which has allowed breeders to introduce specific genes into crops
from the same or different species. In 2004 the first plant genome was fully sequenced, and since
then the number of plant gene sequences in GenBank, the public repository for gene sequence
information, has been doubling every two years. Our knowledge is increasing exponentially, as it
has been in other fields such as semiconductors and cellular telephony.
Our challenge is to increase agricultural yields while decreasing the use of fertilizer, water, fossil
fuels and other negative environmental inputs. Embracing human ingenuity and innovation
seems the most likely path. Plants did not evolve to serve humans, and their sets of genes are
incomplete for our purposes. The integral role of modifying genes is obvious to all breeders,
though sometimes painfully absent from the public’s understanding of how modern agriculture
succeeds. All breeding techniques, from before Mendel’s time until today, exploit modifications
to plant DNA. These modifications can take the form of mistakes or mutations that occur during
natural cell division in the wild; the natural but random movement, or “jumping,” of DNA
sequences from one part of a plant’s genome to another; the random genetic changes induced by
plant breeders; or the more precise insertion of known gene sequences using biotechnology. In
all these cases, plant genes are moved within or across species, creating novel combinations.
Hybrid genetics—the combination of different versions of the same gene—has resulted in
spectacular yield increases. Largely as the consequence of using hybrid seed varieties, corn
yields in the U.S. have increased more than 500 percent in the past 70 years.
Modern genetic tools continue to improve. Breeders are using technologies such as markerassisted breeding, biotechnology and genomics to better measure and understand DNA
alterations and thus increase the precision with which changes are achieved. Insect or disease
protection through biotechnology are being successfully employed in a number of commercial
species, including cotton, papaya, corn and soybeans. Several seed development programs show
promise for reducing water requirements and improving nitrogen utilization (to reduce fertilizer
need) in established crops such as corn and cotton, as well as in new crops such as switchgrass
and miscanthus that are desirable, nonfood feedstocks for biofuels.
Some critics assert that the DNA alterations achieved through biotechnology present unique
health, environmental or social concerns that are not posed by the DNA alterations that result
from other breeding techniques. But the accumulated experience of having safely cultivated and
harvested more than one billion hectares of crops that have been improved through
biotechnology indicates otherwise. Further reassurance can come from the development of sound
science-based regulatory approaches that focus on the proteins generated by DNA alterations,
not the mechanism by which the alterations are created.
It is doubtful that Orville and Wilbur Wright stood on the sands of Kitty Hawk, N.C., and
contemplated space travel, yet a mere 66 years later a human nonetheless stood on the moon.
With modern genetics, increasing crop yields can provide more food, feed, fiber and fuels
without necessarily increasing the need for land, water or fossil fuel, and we should reflect on
what the next 66 years might provide. Perhaps with the right funding and incentives, perennial
grain crops that would not require sowing each year or nitrogen-fixing grain crops that could
drastically reduce fertilizer use might become a reality. More federal funding for plant biology
research—currently dwarfed by biomedical research funding, for example—would help. As
computer pioneer Alan Kay once famously remarked, “The best way to predict the future is to
invent it.”
Note: This article was originally printed with the title, "Breeding Better Crops."