Development of a national inventory of CWR and useful plant species
We have compiled a national inventory1 of taxa representing crop wild relatives (CWR) of the world’s crops, and wild species directly used for food, fiber, forage, medicinal, and other purposes. We defined CWR following Maxted (2006)2 (essentially, close relatives of crops, as defined by belonging to the primary or secondary genepools), but broadened our list to include species within the tertiary genepool, as a number of crops have increasingly benefited from traits introgressed from distant genepools, e.g. pigeonpea3 and beet4, and as these species are also useful for phylogenetics, evolution, and other research5. In general, our method included within the inventory any species within the same genus as the associated crops.
The inventory was created from data sources including the Germplasm Resources Information Network (GRIN) World Economic Plants Database6 based on Wiersema and Leon (1999)7, completed volumes of the Flora of North America8, McGuffin (2000)9 (for herbs and medicinal species), and the Native Seed Network Database10 (for restoration species). Both native and non-native taxa were included. USDA National Plant Germplasm System (NPGS) curators, members of the NPGS Crop Germplasm Committees, and USDA Agricultural Research Service (ARS) crop experts then contributed revisions. The national inventory currently contains 4,600 taxa.
In order to prioritize species within the national inventory for further conservation analyses, we first collated a list of the most important crops around the world, and then identified the crop wild relatives distributed in the U.S. that are related to such crops.