Crop wild relatives

Why they matter

A domesticated crop is, genetically, a narrow slice of the variation present in its wild progenitor species. Domestication tends to fix particular traits (high yield, easy harvest, palatability, uniform ripening) and let other traits (pest resistance, drought tolerance, secondary chemistry) drift. The genetic diversity that doesn’t make it into the domesticated gene pool is preserved, if at all, in the wild relatives — populations of related species growing in the wild centers of crop origin.

These wild relatives are the genetic reservoir to which plant breeders return when the domesticated crop is failing. The mid-20th-century stem-rust epidemics in global wheat were eventually controlled with resistance genes introgressed from Aegilops and Triticum wild relatives. Drought-resistant potato breeding has drawn substantially on wild [[central-andes|Andean]] Solanum species. The genetic diversity that lets cassava continue to adapt to changing pest pressure depends on the wild Manihot populations of [[amazon-basin|Amazonia]] and the [[cerrado|Cerrado]].

The threats

Three structural threats to crop wild relatives:

Habitat loss. Many crop-wild-relative species are restricted to the same regions where their domesticated descendants are now industrially cultivated — and industrial cultivation displaces wild habitat. Wild [[central-andes|Andean]] Solanum populations are increasingly squeezed by potato-and-quinoa expansion. Wild teosinte populations in the Balsas River valley of [[mesoamerica|Mexico]] are threatened by maize expansion and urbanization.

Genetic swamping. When the wild relative grows close to industrially-cultivated domesticated descendants, pollen flow from the cultivated plant can swamp the wild relative’s gene pool. The wild Oryza rufipogon populations of South and Southeast Asia are increasingly hybridized with cultivated rice, eroding the genetic distinctness of the wild population.

Climate change. Many wild relatives are restricted to specific ecological niches that climate change is moving. The wild apple Malus sieversii of the Tian Shan — the genetic source of every cultivated apple on Earth — is undergoing rapid habitat shift as Central Asian climate warms.

Conservation

The Millennium Seed Bank Partnership at Kew, the Global Crop Diversity Trust’s Crop Wild Relatives Project, and the CGIAR network of international agricultural-research centers (CIP for potato, CIMMYT for wheat and maize, IRRI for rice, ICARDA for Fertile Crescent crops) maintain ex situ collections of crop wild relatives. The Svalbard Global Seed Vault holds duplicate backup of many of these collections.

But in situ conservation — protecting the wild populations in their native habitats — is also essential and far less well-resourced. The contemporary recognition that [[indigenous-led-conservation|Indigenous-led conservation]] is often the most effective protection of biodiversity in crop-origin regions ties crop-wild-relative conservation directly to Indigenous land rights — which are also typically the regions where the wild relatives evolved.

See also

Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.

• Shares approach with: [[seed-keeping]]
• Demonstrated by: [[central-andes]] · [[fertile-crescent]] · [[amazon-basin]]

Sources

• Maxted, Nigel et al. (eds.), Crop Wild Relative Conservation and Use (2008)
• Global Crop Diversity Trust — Crop Wild Relatives Project
• Khoury, Colin K. et al., “Origins of food crops connect countries worldwide” (Proc. R. Soc. B 2016)

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A concept entry in the 0mn1.one wiki.