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Colin Khoury1,2, Stephanie Greene3, Nora Patricia Castañeda Alvarez1,41Decision and Policy Analysis Program, International Center for Tropical Agriculture (CIAT), Cali, Colombia email: c.khoury@cgiar.org; 2C. T. de Wit Graduate School Production Ecology & Resource Conservation, Wageningen University, Wageningen, The Netherlands; 3USDA ARS, Prosser, WA, USA; 4Bioversity International, Regional Office for the Americas, Cali, Colombia

Introduction

The wild relatives of crops (CWR), as important genetic resources for crop improvement, represent a dual challenge of requiring conservation as well as access for use. In many regions these resources are threatened by habitat modification, land use changes, and other factors, requiring their urgent collection and long-term availability for research and breeding from ex situ genebank collections, as well as their adequate protection in situ in order to support an evolving genepool for the uses of the future. It is becoming increasingly feasible to formulate a large-scale plan for the efficient and effective conservation of CWR diversity due to advancements in understanding the taxonomic relationships of CWR, in distribution modelling through Geographic Information Systems tools, and in conservation science and technologies. CWR resources are often globally important, yet their management is dependent upon national policy and interests. We suggest that an effective national approach toward the conservation of CWR entails the systematic coverage of this diversity in a network of genetic reserves, with the range of genetic diversity found within these taxa safeguarded in genebanks. We present the work to date on planning for a national effort to conserve CWR and economically important wild taxa occurring in the United States.

Development of a national inventory of CWR and useful species

We are compiling a national inventory of taxa representing CWR of the world’s crops, and wild species directly used for food, fiber, forage, medicinal, and other purposes. With the aim of including as many species as possible with the potential to contribute to crop improvement, we defined CWR following Maxted (2006)1, broadened to include species within the tertiary genepool. The national inventory was compiled from data sources including the Germplasm Resources Information Network (GRIN) World Economic Plants Database2, based on Wiersema and Leon (1999)3; completed volumes of the Flora of North America4; McGuffin (2000)5 (for herbs and medicinal species); and the Native Seed Network Database6 (for restoration species). Both native and non-native taxa were included. USDA National Plant Germplasm System (NPGS) curators and crop experts then contributed revisions. The national inventory currently contains over 3,000 taxa.

Prioritizing genepools based on potential use value

Given limited resources, a national conservation strategy for CWR requires the prioritization of species based upon their potential use value, particularly in contributing to agriculture through crop breeding. This necessarily limits the term ‘crop’ to those cultivated species with modern cultivar forms and active breeding programs.

We compiled a list of the world’s major crops from FAOSTAT global production and consumption data7; crops listed in Annex 1 of the International Treaty on Plant Genetic Resources for Food and Agriculture8; and the major and minor crops listed in Appendix 2 of the World Atlas of Biodiversity9 and in Prescott-Allen and Prescott-Allen (1990)10. Crops on the collated list were then categorized by importance, with the major crops given highest priority. The national inventory was then reviewed in order to identify CWR taxa of high potential use value that were not already included within the priority crop list, as well as for identification of taxa of significant direct use value to food production or to the economy in the U.S. (e.g. sugar maple (Acer saccharum), wild rice (Zizania spp.), and pecan (Carya illinoinensis). These taxa were included in the prioritization as iconic valuable wild species occurring in the US. Finally, any additional genera known to be included within the genepools of the crops on the priority lists were added (e.g. Aegilops for wheat, Tripsacum for maize).

The resulting list of the world’s major crop genepools includes 255 crops/281 genera (108 crops/126 genera in Priority 1; 147 crops/155 genera in Priority 2). This list includes all the most important agricultural crops around the world by a number of measures, and covers all major crops listed in FAOSTAT for US production and food supply7.

Priority taxa for a national CWR conservation strategy

2,012 taxa of 159 priority genera occur in the US- 904 taxa of 74 Priority 1 genera (Table 1), and 1,108 taxa of 85 Priority 2 genera. Important crops with rich native genepools include Allium (onion), Cucurbita (squash), Fragaria (strawberry), Helianthus (sunflower), Ipomoea (sweet potato), Lactuca (lettuce), Phaseolus (bean), Prunus (cherry, almond, peach), Ribes (currant), Rubus (raspberry), Saccharum (sugar cane), Vaccinium (blueberry, cranberry), and Vitis (grape).

To target conservation efforts for a national conservation strategy, we focused on Priority 1 genepools. This focus includes the richest genepools of native diversity occurring in the US that have the potential to contribute to crop improvement, and also attempts to cover the major wild species directly utilized for food or medicine. The Priority 1 list is currently under review by crop breeders and genetic resources experts. 

Within these genepools, we will prioritize taxa by degree of relatedness to the crop (i.e. genepool concepts1,11). Those closely related taxa (GP1 and GP2), and other taxa known to be utilized in crop breeding, will be subjected to a full gap analysis for identification of collecting priorities, and for in situ conservation considerations. For the distantly related taxa, a superficial gap analysis will identify taxa not conserved ex situ by at least a few populations, and prioritize these for additional collecting. Any taxa identified as rare or threatened will be given particular attention in conservation recommendations.

Next steps toward a national CWR conservation strategy

We will utilize a “gap analysis” method aimed at identifying locations of genetic diversity in the US un- or under- secured in conservation systems12, in order to inform planning of germplasm collecting for ex situ conservation13, as well as to identify key areas in order to make recommendations for in situ conservation. We are gathering and geo-referencing species occurrence and conservation data from online resources, herbarium and genebank databases, and in collaboration with researchers. The results of the gap analyses will form the basis for a prioritization of taxa across genepools for collecting, and the identification of the highest priority locations for the most efficient and effective collecting as well as for the establishment of protected areas for CWR (Figure 1).

References

1Maxted N, Ford-Lloyd BV, Jury SL, Kell SP and Scholten MA (2006) Towards a definition of a crop wild relative. Biodiversity and Conservation 15(8): 2673–2685.

2USDA ARS National Genetic Resources Program, Germplasm Resources Information Network (GRIN). Available online at: http://www.ars-grin.gov/cgi-bin/npgs/html/wep.pl.

3Wiersema J and Leon B (1999) World Economic Plants: A Standard Reference. Boca Raton (FL): CRC Press LLC.

4Flora of North America Association (2008) Flora of North America. Available online at: http://fna.huh.harvard.edu/.

5McGuffin M and American Herbal Products Association (2000) Herbs of commerce. 2nd ed. [S.l.]: American Herbal Products Association.

6Native Seed Network (2010) Native Seed Network Database. Available online at: www.nativeseednetwork.org.

7FAO (2011) FAOSTAT Agricultural production domain. FAO, Rome, Italy. Available online at: http://faostat.fao.org/.

8FAO (2002) International Treaty on Plant Genetic Resources for Food and Agriculture. Food and Agriculture Organization of the United Nations, Rome, Italy.

9Groombridge B and Jenkins MD (2002) World Atlas of Biodiversity. Prepared by the UNEP World Conservation Monitoring Centre. University of California Press, Berkeley, California.

10Prescott-Allen R and Prescott-Allen C (1990) How Many Plants Feed the World?. Conservation Biology 4 (4): 365-374.

11Harlan JR and de Wet JMJ (1971) Toward a Rational Classification of Cultivated Plants. Taxon 20 (4): 509.

12Maxted N, Dulloo E, Ford-Lloyd BV, Iriondo JM, and Jarvis A (2008) Gap analysis: a tool for complementary genetic conservation assessment. Diversity and Distributions 14 (6): 1018-1030.

13Ramírez-Villegas J, Khoury C, Jarvis A, Debouck DG and Guarino L (2010) A Gap Analysis Methodology for Collecting Crop Genepools: A Case Study with Phaseolus Beans. PLoS ONE 5(10), e13497.

CWR photos from www.plantsystematics.org

Acer Carya Elymus Leymus Prunus Trifolium

Aegilops Cinnamomum Ficus Linum Psathyrostachys Tripsacum

Agave Cocos Foeniculum Malus Pseudoroegneria Vaccinium

Agropyron Colocasia Fragaria Manihot Psidium Vanilla

Allium Corylus Gossypium Medicago Pyrus Vernicia

Artocarpus Cucumis Helianthus Olea Ribes Vicia

Asparagus Cucurbita Hordeum Papaver Rubus Vigna

Avena Cynara Ilex Pennisetum Saccharum Vitis

Beta Daucus Illicium Persea Simmondsia Zizania

Brassica Dioscorea Ipomoea Phaseolus Solanum

Capsicum Diospyros Juglans Pinus Sorghum

Carica Diplotaxis Lactuca Piper Syzygium

Carthamus Echinacea Lathyrus Pistacia Thinopyrum

Collaborate with us!The gap analysis method is dependent upon the quality of data utilized. Important species occurrence data are not easily available online, and ecogeographic datasets benefit significantly from expert review. We would therefore like to ask for your collaboration in sharing with the project occurrence and conservation data on the priority genera. If you have expertise in the taxonomic and genetic relationships within the genepools, or in the distribution and/or conservation status of taxa, we would appreciate your inputs for validating the results of the taxonomic work and the gap analyses. Please contact us at c.khoury@cgiar.org.

Table 1: Priority 1 Genera

Figure 1: wild Phaseolus and protected areas in the SW US

Cucurbita foetidissima Juglans hindsii Vitis rotundifolia

Vaccinium oxycoccos Rubus hawaiensis

Initial Steps toward a National Conservation Strategy for Crop Wild Relatives of the United States