Climate change

What can the wild chile teach us about conserving crop wild relatives?

There is a humble, wild chile pepper that grows in Arizona. Commonly called chiltepín, it is the wild relative of hundreds of domesticated pepper varieties grown (and eaten) all over the world. My research involves a new vision to conserve these wild relatives called “trans situ conservation.”

The wild chile may seem unassuming. It’s a small pepper. On the north end of the Sonoran Desert, plants are often found nestled among larger shrubs and rocks. Most of the year, they are nearly indistinguishable from other bushes. But, in the fall, their spicy, small round chiles ripen to bright red, enticing birds and humans alike.

wild chile plant
Ripe wild chile fruits on the living plant collections at the Arizona-Sonora Desert Museum located in Tucson, Arizona. Image credit: Erin C. Riordan

Wild plants closely related to crops are called crop wild relatives. They are often more tolerant of stressful growing conditions like heat, drought, and pests than their domesticated cousins. These wild species contain information that scientists can use to create solutions to increase food security and sustainability.

These efforts, however, require the conservation of crop wild relatives. This happens “in situ” – in their native habitats, where they can continue to evolve with changing climates and pests. And, it happens “ex situ” – out of their habitats, in gene banks and gardens. There, they are studied and used for plant breeding.

Unfortunately, most crop wild relatives are poorly studied. They have become increasingly threatened in the wild, and are poorly collected. My research colleagues and I have developed program to ensure the conservation these important crop species.

Called “trans situ” conservation, our process aims to fill gaps in knowledge, conservation, and use. We integrate several types of conservation methods to create a safety net:

  1. In situ protection, management, and research;
  2. local and regional ex situ plant collections maintained for conservation, research, and education; and,
  3. national and global gene bank repositories for plant breeding and crop research.

Decades of wild chile research and conservation in southern Arizona inspire this trans situ conservation model. Overharvesting and increasing habitat loss brought conservationists, researchers, and natural resource managers together in 1999 to establish the Wild Chile Botanical Area. This is the first preserve in the United States designated specifically for crop wild relative protection.

Chile landscape
Wild Chile Botanical Area, Coronado National Forest. Image credit: Perin McNelis, Borderlands Restoration Network

Over the years, the wild chile has taught us important conservation lessons. We learned that the chiles cannot be conserved in the wild without also protecting ecological relationships. Shrubs often found accompanying chiltepín plants at the northern range limit protect the chile from damaging frost. These so-called “nurse plants” are also important habitat for migratory birds. The birds feast on ripe wild chiles, and deposit ready-to-germinate seeds into the protective understory. Chiltepin persistence in the wild depends on both nurse plants and birds. The plant’s survival may suffer if climate change interferes with the timing of chile fruiting with the arrival of migratory bird visits.

The wild chile also teaches us that conservation outside of native habitats is important. Collecting and storing seeds and tissues off site provides an important back-up against threats like climate change and invasive species. Both local off-site collections and large, national gene bank repositories are vital and complement one another.

Just like libraries, seed banks preserve some of our most important information – in this case plant information. Ex situ (off-site) collections at the Native Seeds/Search seedbank include 185 accessions of 40 different crop wild relatives. Credit: Native Seeds/SEARCH

National repositories, like the US National Plant Germplasm System, facilitate access to plant materials for large-scale crop research and plant breeding. Botanical gardens and museums, like the Arizona-Sonora Desert Museum, house local seed and living collections. They also support research and educate the public about the value and conservation importance of wild plants. The non-profit Native Seeds/SEARCH(NS/S), which was instrumental in the wild chile’s conservation, conserves seeds and also promotes use of locally-adapted plant materials otherwise inaccessible to local communities.

Perhaps the most important lesson from the wild chile is that, when combined, these individual ingredients of protection, collection, research, and education result in a powerful recipe for success. The conservation value of the wild chile has been recognized federally, regionally, and locally. Foresters in Arizona have given the species a special “sensitive” status. This helped curb overexploitation in the wild.

dried chiles
Dried chiles sold at a roadside stand in Sonora, Mexico. Regional culinary traditions of southern Arizona and Sonora continue to celebrate the fiery peppers. Image credit: Erin C. Riordan

While this success story is encouraging, much work is still needed to conserve crop wild relatives, especially in the Sonoran Desert. Here, wild plants have evolved a remarkable number of strategies to cope with severe conditions. Their ability to survive poor soils, heat, and scarce and unpredictable rainfall may hold the key for breeding crops of the future.

Scientists, conservationists, and landowners will need to work together to identify and fill gaps in conservation. Our food security may rely on these wild and tough desert survivors.

Provided by Erin Riordan, University of Arizona

Adapted from Dr. Riordan’s paper Trans Situ Conservation of Crop Wild Relatives

Visit our main Crop Wild Relative Page to see all our blogs, stories, a video – and even deeper academic research! To read about how flax could become perennial using crop wild relatives here. Learn about why some crop wild relative plants are best preserved as tissue by reading this blog.

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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