Our native crop wild relatives have proved useful as genetic resources in breeding more productive, nutritious, and resilient crops. Their utilization is expected only to increase with better information on the species and improving breeding tools, but may well be constrained by their limited representation in seedbanks and the ongoing loss of wild populations due to habitat modification, invasive species, climate change and other impacts. Urgent collecting and habitat conservation efforts for native crop genetic resources are therefore warranted. We present foundational information needed to guide this effort. An inventory of U.S. crop wild relatives has prioritized taxa related to a broad range of important food, forage and feed, medicinal, ornamental, and industrial crops. Utilizing occurrence data gathered from herbaria and genebanks, resulting potential distribution models are enabling the identification of hotspots of taxonomic diversity of wild relatives in the country, and a ‘gap analysis’ methodology is facilitating efforts to identify those taxa and geographic areas of particular conservation concern. Results indicate that a broad range of wild relative diversity remains to be collected. Numerous populations of high priority taxa could be actively managed in existing conservation areas, although many are distributed in areas without long-term habitat protection. We discuss the value of collaboration across agriculture and natural resources management organizations to better conserve our nation’s heritage of crop wild relatives.

1. 1USDA, Agricultural Research Service, Center for Agricultural Resources Research, National Laboratory for Genetic Resources Preservation, 1111 S. Mason St. Fort Collins, CO 80521 (Stephanie.Greene@ars.usda.gov);
1USDA, Agricultural Research Service, Center for Agricultural Resources Research, National Laboratory for Genetic Resources Preservation, 1111 S. Mason St. Fort Collins, CO 80521 (Colin.Khoury@ars.usda.gov);
3International Center for Tropical Agriculture (CIAT) c.khoury@cgiar.org
4 USDA, Agricultural Research Service ,National Germplasm Resources Laboratory, United States Department of Agriculture, Agricultural Research Service. Karen.Williams@ars.usda.gov
5International Center for Tropical Agriculture (CIAT). c.sosa@cgiar.org
Distributions and Conservation Priorities for Crop Wild
Relatives of the United States
Stephanie L. Greene1, Colin K. Khoury2,3, Karen A. Williams4, and Chrystian C. Sosa5
INTRODUCTION
The value of our native CWR in breeding more productive, nutritious and
resilient crops has been clearly demonstrated and will increase in the future.
Their utilization is constrained by their limited representation in seedbanks and
the ongoing loss of wild populations due to habitat modification, invasive
species, climate change and other impacts.
UNITED STATES CROP WILD RELATIVE INVENTORY
The national inventory (Khoury et al. 2013) recognized 2500 taxa of CWR in
the US.
• 60% related to food crops
• Fruits and nuts- strawberry, blueberry, cranberry, stone
fruits, grape, pecan
• Vegetables- peppers, squash, lettuce, sweet potato, squash
• Cereals, pulses and oils- bean, quinoa, sunflower
• 28% related to forage and feed crops
• 12% related to medicinal, ornamental, material and industrial crops.
Khoury et al. (2013) prioritized the national inventory based on perceived
value to contribute to breeding programs using concepts of Wiersema and
León (2016) and the Harlan and de Wet Crop Wild Relative Inventory
(Vincent et al. 2012).
• Highest priority (P1) CWR taxa- defined as taxa related to important
food crops.
• P1A taxa (native and closely related to crops) – 281 taxa
• P1B taxa (either non-native or native but distantly related to
crops)- 536 taxa
WHERE ARE CWR LOCATED IN THE UNITED STATES?
Utilizing occurrence data gathered from herbaria and genebanks,
distribution models are enabling the identification of hotspots of taxonomic
diversity of wild relatives in the country, and a ‘gap analysis’ methodology is
facilitating efforts to identify those taxa and geographic areas of particular
conservation concern.
What is a Crop Wild Relative?
“a wild plant taxon that has an indirect use derived from its relatively close
genetic relationship to a crop” (Maxted 2006)
CONCLUSION
Results of the gap analysis indicate that a broad range of wild relative
diversity remains to be collected so they can be conserved in gene banks
where they are available for use. In situ conservation could be effective in
existing natural areas, although many are distributed in areas without long-
term habitat protection. Because the USDA ARS is not a land management
agency, effective conservation will depend upon successful partnerships
between agricultural and natural areas communities. Innovative alliances
are already being forged with the BLM and USFS. Working together we can
better conserve our nation’s heritage of crop wild relatives.
REFERENCES
Khoury CK, S Greene, J Wiersema, N Maxted, A Jarvis, and PC Struik. (2013) An Inventory of Crop Wild Relatives of the United States.
Crop Science 53: 1496 – 1508. doi: 10.2135/cropsci2012.10.0585
Seiler GJ, Qi LL, Marek LF (2017) Utilization of Sunflower Crop Wild Relatives for Cultivated Sunflower Improvement. Crop Sci
oi:10.2135/cropsci2016.10.0856
Wiersema JH and B León. 2016. The GRIN Taxonomy Crop Wild Relative Inventory. pp 453-457 in N Maxted, EH Dulloo and BV Ford-Lloyd
(eds) Enhancing Crop Genepool Use: Capturing Wild Relative and Landrace Diversity for Crop Improvement. CAB International, Oxford,
United Kingdom.
Vincent, H.A., J.H. Wiersema, S.L. Dobbie, S.P. Kell, H. Fielder, N.P. Castañeda Alvarez, L.
Guarino, R. Eastwood, B. Leon, and N. Maxted. 2012. A prioritized crop wild relative
inventory to help underpin global food security. Available at https://www.cwrdiversity.org/checklist/
Fig 1 is a crop wild relative richness map of the
United States based on 395 taxa identified as high
priority species. Genera include many species of
Rubus, Prunus, Coreopsis, Vaccinium, Rudbeckia, and
Ribes
Fig 2 illustrates the occurrence of four
crop wild relative species that are
threatened or endangered. Points are
occurrence points (from herbaria and
genebanks); the models are the
potential distribution models based
on similar climate and soils.
SOME CWR SPECIES ARE VULNERABLE
• 8 - critically imperiled (G1), including 2 species of Helianthus and Juglans
hindsii, GP 2 of walnut
• 22 - globally imperiled (G2), including Tripsicum floridanum, in GP 3 for
maize and Rubus macraei, in GP 2 for red raspberry
• 88 - globally vulnerable (G3)
MOST CWR ARE COMMON, EVEN WEEDY
Fig 3 illustrates the occurrence of
three important sunflower crop wild
relative species. The estimated annual
economic contribution of the wild
species for cultivated sunflower is
between $267 to $384 million USD
(Seiler et al. 2017).
Tripsacum dactyloides Helianthus paradoxus
Rubus hawaiensis
Juglans hindsii
Fragaria virginiana
Vitis labrusca
Vaccinium corymbosum