Every plant that we eat, wear or feed our livestock with has a cousin that grows in the wild. Carefully selected and bred for desirable traits over millennia, the crops we enjoy today are a link to an ancient past strongly tied to culture and place.
Unlike our own ancestors, the forebears of our favorite crops can still be found – but many are in danger of extinction. Yet as these historical strains grow scarcer, they’re are also more important than ever to our food security.
Crop wild relatives are the wild plants from which modern crops were domesticated. They have adapted to the conditions of their native habitats, picking up genetic traits that enhance their resistance to diseases, drought or other crop killers.
As modern crops are largely standardized, they lack genetic diversity, making it difficult for them to adapt to the climate crisis, which is shifting seasonal patterns and introducing pests to new areas.
That’s where crop wild relatives come in, as they can be interbred with modern crop varieties to give them the genetic traits to withstand these shocks – thus protecting the entire global food system.
Now, let’s take a tour around the world and through the past to find the crop wild relatives of a few of our favorite foods.
Wheat, or the genus Triticum, is a domesticated grass that is now the world’s most widely grown food crop in terms of cultivated land area.
Most of the wheat we consume today is common wheat (Triticum aestivum). Its wild relatives include einkorn and emmer wheats, which were cultivated as early as 12,000 to 9,000 years ago.
Scholars believe einkorn wheat (Triticum monococcum) was first domesticated in the Karacadağ Mountains in southeastern Turkey. Emmer (Triticum dicoccum) also originates from the same region but is now only grown in pockets of Europe and Asia.
This includes Italy, where emmer is known as farro and has been grown since 30 BC when Julius Caesar invaded Egypt, where it was a nutritious staple at the time. The wheat went on to feed the Roman Empire and gave rise to the modern Italian word for flour: farina.
Wild emmer has been found to be high in protein, while wild einkorn is known for its resistance to leaf rust and nematodes.
Research has also shown wild emmer to be a good source of genes for increasing resistance to heat stress in wheat – a particularly useful trait in today’s warming world.
Citrus fruits come in all shapes and flavors, from the bitter grapefruit to the sweet clementine. Yet most of the world’s commercially important citruses have been crossbred from just three original fruits.
One of these is the mandarin orange (Citrus reticulata), native to southern China’s Nanling Mountains. Unlike modern mandarins, which have been sweetened through crossbreeding with pomelos, wild mandarins are sour.
While the lineages of citrus fruits are still debated, wild mandarin oranges are thought to be one of the progenitors of sour oranges, sweet oranges, grapefruits, lemons and some limes.
But this shared ancestry – hence lack of genetic diversity – also makes them vulnerable to disease outbreaks.
Citrus greening disease, which deforms fruits and eventually kills off entire trees, has devastated citrus harvests globally. In the U.S. state of Florida, it has contributed to a 90-percent drop in orange production over the past 20 years. Now, the climate crisis may be causing this pathogen to spread to new areas like southern Europe.
Potatoes (Solanum tuberosum) are the world’s most important tuber crop and are eaten on every continent. The highly nutritious potato was first domesticated in South America’s Andes Mountains roughly 8,000 to 10,000 years ago.
After colonizing South America, the Spanish introduced potatoes to Europe, where they became a widespread staple crop and caused the continent’s population to explode.
Unfortunately, the crop’s lack of genetic diversity made it vulnerable to diseases like late blight, which devastated Ireland’s potato yield in the mid-19th century and contributed to the country’s Great Famine.
More than 150 species of wild potato grow in the Central Andes region. While most are too bitter and small to eat, they are highly tolerant to extreme conditions such as freezing temperatures, heat and drought, as well as pests and disease.
Scientists are now tapping into these genes to create hardier potatoes. For example, researchers with the Crop Trust have used a wild relative to breed a new potato variety that has near total resistance to late blight, releasing it to Peruvian farmers in 2021. Wild potatoes are also being developed to withstand heat, drought and bacterial wilt disease.
Soybeans (Glycine max) are the world’s most grown legume and the fourth most widely grown crop in the world by cultivated area.
While they feature in many Asian diets, notably in the form of tofu and soy milk, the vast majority of the world’s soybeans are grown for animal feed, which is a major driver of deforestation in the Amazon rainforest.
Soybeans are thought to have been domesticated in East Asia roughly 6,000 to 9,000 years ago, spreading globally over millennia. Their closest living relative is the wild soybean (Glycine soja), a vine-like plant bred over time to have the shorter stems and larger beans seen in modern soybeans.
However, soybeans can be highly vulnerable to cyst nematodes. While new soybean varieties have been developed to resist them, they’re mostly bred from a small gene pool, making this resistance potentially easy to overcome.
More genetically diverse wild soybeans have been found to contain more effective nematode-resistant genes, possibly offering more safeguards against these devastating pests.
The sheer variety of vegetables that come from the Brassica oleracea species is astounding. Kale, cauliflower, collard greens, cabbage, gai lan, Brussels sprouts, kohlrabi and broccoli are all technically the same species, but each bred differently to emphasize specific parts of their anatomy, such as leaves, buds or stems.
The origins of Brassicas oleracea greens remain unclear. What we do know is that wild cabbage likely originated in the Eastern Mediterranean, and references to cabbage began appearing in Greek literature around 2,500 years ago. Wild cabbage is still found growing on chalky coasts across Europe today.
Brassica crops are vulnerable to diseases such as turnip mosaic virus, black rot and Fusarium wilt. Researchers have been looking to wild Brassica relatives for disease-resistant genes, including crossbreeding them with cauliflower to develop resistance to black rot.
Like other wild plants, crop wild relatives face threats from habitat degradation, including the introduction of invasive species, overexploitation and overuse of pesticides or herbicides.
The development of industrial agriculture, with its emphasis on monocultures, has also reduced the genetic variety of crops, while globalization continues to homogenize global diets.
The primary method for conserving crop wild relatives is in situ – protecting them where they grow in the wild. This involves designating site for monitoring and conserving the species.
As a backup, these plants can also be conserved ex situ, which entails collecting and preserving seeds and plant parts.
According to the Crop Trust, both types of conservation remain inadequate. There are few examples of in situ protection for crop wild relatives, and even ex situ collections contain only a small number of wild samples.
Nevertheless, initiatives like the Crop Wild Relatives Project are aiming to preserve the genetic bounty of wild crops. The project collects seeds from crop wild relatives, uncovers useful genes, and pre-breeds them into varieties that can be more easily bred with cultivated varieties to introduce these genes.
Such initiatives are an important first step in protecting valuable genetic diversity in a world facing disruptions to agriculture due to the climate crisis and the rapid spread of devastating diseases due to globalization.
In other words, these crops of the past could be key to saving the future of our food.
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