Climate change

Conserving wild crop cousins

Farmers are experiencing a turbulent ride navigating our unpredictable weather. We rely on them to produce food, fiber and other plant-based items the world relies on in our everyday lives. Developing crops that can handle the vagaries of nature is an important strategy for handling climate change. Domestication through breeding made species easier to farm, higher yielding and more nutritious. Yet, it came with the trade-off of a loss of diversity, since potentially useful traits were left behind in the wild.

small green gourd that is a relative of pumpkin
Endangered crop wild relatives include Okeechobee gourd, a relative of squash and pumpkin. Provided by Stephanie Greene USDA

Plant breeders are increasingly turning to close “wild cousins” of crops, hoping to rediscover useful traits. These “crop wild relatives,” as breeders call them, have not undergone any type of domestication. Samples are wild strawberries and apples, native forms of lettuce, and even native beans. Their fruits, grains and roots are not as large as domesticated crops. Some might be bitter, or have poor texture. But, these hardy plants have traits that helped them live in some harsh conditions. And, these traits are useful to breeders in the fight to create a sustainable and secure food supply.

Breeders can use these species because they interbreed with their more modern crop relatives. New genetic tools make the process of incorporating useful wild variants into domesticated types more efficient. Crop wild relatives are some of the most promising resources that plant breeders can use to develop cultivars adapted to extreme conditions. These crop wild relatives hold promise to resolve today’s agricultural problems. Ironically, they are also vulnerable to climate change, and threats such as habitat modification, pollution, invasive species, and other human impacts.

Envelopes with coding pertaining to the seeds inside them - and a few scattered potato seeds
Packets and seeds collected and preserved by the efforts of scientists at the USDA and other research institutions. Credit: SV Fisk

The first step to conserving crop wild relatives is to identify and inventory them. A growing list of countries, including the United States and Mexico have published national inventories. Canada has identified the need for an inventory as a priority. The Crop Science Society of America’s journal, Crop Science, has published both the US and Mexico inventories1.

A global inventory of 1,667 crop wild relative species of 173 globally important crops, provided interesting information on the status of crop wild relatives in North America. First, North America is an important source of crop wild relatives. Canada possessed crop wild relatives closely related to sunflower, currant, gooseberry, and strawberry. Mexico was rich in many species, especially close relatives to maize and bean. The United States also had many species, relatives closely related to sunflower, grape, stone fruits, and small fruits (blackberry, blueberry, etc.)

Wild-RelativeF400Second, many of these species are vulnerable, and not secured in gene banks. Some are vulnerable to extinction. The United States inventory of crop wild relatives contains 3,500 species! Five species are known or presumed to be extinct in the wild. Four percent of the inventory were ranked as “globally critically imperiled” or “imperiled.” Almost six percent were “vulnerable.” This highlights the need for finding and preserving the germplasm of crop wild relatives. (To read more about seed preservation, visit this blog.)

Species identified as high priority to collect and conserve include:

  • Cucurbita okeechobeensis, a close relative of squash;
  • Chiloensis sandwicensis, related to strawberry,
  • Helianthus niveus Tephrodes; a close sunflower relative; and
  • Manihot walkerae, a relative of cassava.
Yellow flower with brown seeds in the middle - a small sunflower relative
Endangered crop wild relatives include the Pecos sunflower, a relative of sunflower. Provided by Stephanie Greene USDA

Although many crop wild relatives are common, their representation is also limited in gene banks. There is a need to identify where crop wild relatives occur, and protect them in their natural habitats. Equally important is their collection and preserving in gene banks, where they can be readily sent to scientists and plant breeders.

Conservation of wild plant genetic resources requires the cooperation of many players: different federal, state and tribal agencies, non-governmental organizations including botanical gardens and academic institutes, and, increasingly, citizen scientists and other local groups. Sometimes the emphasis on making wild genetic resources available for use can conflict with concerns about over-harvesting or maintaining the genetic integrity of original populations.

Open discussion can lead to innovative solutions that meet different organizational missions while moving native plant conservation objectives forward. Extinction of crop wild relatives will be a permanent and irreversible loss. Conserving the valuable crop wild relative species of North America is technically feasible. We have adequate resources. We have the scientific ability to complete the tasks. There is no technical reason why North American wild plant genetic resources should be inaccessible to plant breeders and scientists, much less become extinct.

Provided by Stephanie Greene, USDA-ARS, Colorado

Read about more crop wild relatives in these blogs!

Frank Meyer, an early plant explorer

Yams, a main staple in Africa, Asia

The cranberry: a very American berry

Call of the wild sunflower

And, be sure to visit our main Crop Wild Relative Week page for more information!

  1. A Crop Wild Relative Inventory for Mexico Crop Science, 2018:, doi: 2135/cropsci2017.07.0452 and An Inventory of Crop Wild Relatives of the United States Crop Science, 2013:,  doi:10.2135/cropsci2012.10.0585

About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.

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