Significance: This study provides conservation assessments for 600 US native plants that are wild relatives of important agricultural crops. We found that more than one-half of the species may be endangered in their natural habitats, and that the great majority require further conservation action, both ex situ (in gene banks and botanical gardens) and in situ (in protected areas). Diversity hotspots across the nation represent focal regions for further collecting for ex situ conservation as well as for enhanced habitat protection. Wider collaborations, as well as greater awareness, access to, and information about these resources are needed to bolster their conservation and use.

Knowledge of the genetic diversity in populations of crop wild relatives (CWR) can inform effective strategies for their conservation and facilitate utilization to solve agricultural challenges. Two crop wild relatives of the cultivated cranberry are widely distributed in the US. We studied 21 populations of Vaccinium macrocarpon Aiton and 24 populations of Vaccinium oxycoccos L. across much of their native ranges in the US using 32 simple sequence repeat (SSR) markers. We observed high levels of heterozygosity for both species across populations with private alleles ranging from 0 to 26. For V. macrocarpon, we found a total of 613 alleles and high levels of heterozygosity (H_O = 0.99, H_T = 0.75). We also observed high numbers of alleles (881) and levels of heterozygosity (H_O = 0.71, H_T = 0.80) in V. oxycoccos (4x). Our genetic analyses confirmed the field identification of a native population of V. macrocarpon on the Okanogan-Wenatchee National Forest in the state of Washington, far outside the previously reported range for the species. Our results will help to inform efforts of the United States Department of Agriculture Agricultural Research Service (USDA-ARS) and the United States Forest Service (USFS) to conserve the most diverse and unique wild cranberry populations through ex situ preservation of germplasm and in situ conservation in designated sites on National Forests.

The Plant Exploration Program was established by USDA in 1898, several decades before the emergence of the US National Plant Germplasm System (NPGS), and continues to support international and domestic plant explorations for germplasm acquisition. These explorations are designed to fill collection gaps identified by the crop curators of the NPGS and the 40 Crop Germplasm Committees that counsel the NPGS. About 15 explorations are conducted annually under the auspices of this program. Although plant explorations to remote areas are often still the only means of acquiring unique new germplasm, the focus and methods applied by modern plant explorers have changed significantly in recent years in response to evolving germplasm needs and the new opportunities presented by recent technological advances. Modern explorations are characterized by the targeting of specific taxa and traits. New exploration techniques and tools, including geographic information systems and improved methods of data collection, are being applied to locate, document, and assess plant genetic diversity. During the past decade, legal obstacles faced by the Program have increased due to restrictive laws implemented in germplasm donor countries that exercise their national sovereignty over genetic resources, replacing the free and open access to genetic resources that prevailed before the ratification of the Convention on Biological Diversity in 1993. The NPGS has responded to these regulatory challenges with a flexible approach that includes nonmonetary benefit sharing and increased partnerships with host countries.