Sustaining the World’s Food Supply

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Written by Achim Walter

In the midst of today’s organic food boom and romantic glorification of nature, plant breeding is in a difficult position: one often forgets that we as humans owe our very survival to the supply of food. Almost nothing that we eat today would have existed 10,000 years ago in the natural world.

Humans can do without many things, but not food. Ultimately, plants produce every calorie we consume to provide ourselves with biochemical energy. Every little daisy in the world can perform photosynthesis, but we cannot. Yet, even the most advanced plant breeding methods cannot transform a daisy into a source of calories. Nor should these methods, because a long time ago our ancestors discovered ways to exploit other plant species that are “naturally” better suited.

Human Culture at its Roots

As early as 10,000 years ago, humans selected the best individual specimens from the precursors of today’s maize, wheat, rice and apples, and tried to make them more resistant by “forcing” them to breed with the same or different varieties. For thousands of years, “human selection” was the law of the land. Its success led to greater yields and better tasting food.

About 2,000 years ago, the apple tree had already become a cultivated chimera, when our forebearers grafted the fruit-bearing stem on to the root system of a different variety – a highly advanced biotechnological process for the time. What happened?

The effect of continuous selection: From the slight teosinte to massive corncob. (Image: Wikimedia / John Doebley)

Gradually, humans cultivated modern crops from their wild progenitors. The wheat and spelt we eat today are hybrids created from crossing the genomes of three wild species. Maize with its oversized cobs is a descendent of the shrubby teosinte. Clones of apples, vines and other fruit trees also experienced a loss of innocence – no longer fruits of the forest and meadow flora, once grafted onto rootstock capable of keeping soil-borne pathogens in check.

Wheat, Rice and Corn under Threat

These kinds of optimized plants, considered a blessing at the time, steadily increased yields enabling our ancestors to advance both economically and culturally. The world’s population grew and the “big three” – wheat, rice and corn – continue to provide more than half of our food supply today. We cannot replace these calorie kings, but our dependence on these staples has become a curse.

Our crops have a serious problem and; therefore, we have a problem. Crops must constantly fight off disease. While we could say the same for all living things, it is particularly acute for our agricultural all-star athletes. This is because the more we grow them, the more aggressive pests and pathogens become – and the risk of disease increases.

Plant breeding is one of our most important weapons in this race. It is nothing more than a highly selective dating service that creates new disease-resistant varieties through many years of selection and with great effort. For years, scientists have been trying to make crops permanently resistant [1], unfortunately, to no avail. Avoiding resistance improvement is not an option. Stagnation leads to regression – a future without breeding would be like a world without medicine.

This is also the reason why researchers hold out high hopes for modern breeding techniques such as CRISPR/Cas9. This genome editing system allows individual genes to be specifically modified or deactivated, without the incorporation of foreign genetic material. Enabling, in turn, the development of highly resistant plants genetically indistinguishable from conventionally bred varieties. Even organic farmers may be interested in this development [2]. Currently, organic farmers must treat potatoes with large amounts of copper in order to keep late blight in check. A resistant variety would be a benefit to humankind, even if it came about through genome editing.

Sustainable Cultivation

So let us not fool ourselves. Almost nothing we eat today, whether organic or conventional, was found in nature 10,000 years ago. Today’s major crop varieties must be adapted to survive in a changing environment. Not from year to year, but in increasingly rapid succession.

We will also need to diversify our fields. To feed the world more sustainably, we need both more plant species and more resistant varieties of these species. Further, the varieties must be of top quality and yield, conserve soil and water, and require as little fertilizer and pesticides as possible. This ideal path towards sustainable agriculture requires both new plant breeding methods and ecological cultivation of our crops. This bilateral approach is not mutually exclusive, but rather complementary.

About the author: Achim Walter is a Professor of Crop Science in the Institute of Agricultural Sciences at ETH Zurich. Professor Walter focuses on non-invasive, dynamic characterization of plant growth, applying results to increase the efficiency of crops and agro systems.

Editor’s Note: This article was originally published in ETH Zurich’s Zukunftsblog (Future blog).