Distributions and Conservation Status of Carrot Wild Relatives in Tunisia: A Case Study in the Western Mediterranean Basin

Crop wild relatives, the wild progenitors and closely related cousins of cultivated plant species, are sources of valuable genetic resources for crop improvement. Persisting gaps in knowledge of taxonomy, distributions, and characterization for traits of interest constrain their expanded use in plant breeding and likewise negatively affect ex situ (in genebanks) and in situ (in natural habitats) conservation planning. We compile the state of knowledge on the taxonomy and distributions of the wild relatives of carrot (genus Daucus L.) natively occurring within Tunisia—a hotspot of diversity of the genus, containing 13 taxa (27% of species worldwide). We use ecogeographic information to characterize their potential adaptations to abiotic stresses of interest in crop breeding and assess their ex situ and in situ conservation status. We find substantial ecogeographic variation both across taxa and between populations within taxa, with regard to adaptation to high temperatures, low precipitation, and other traits of potential interest. We categorize three of the taxa high priority for further conservation both ex situ and in situ, five medium priority, and five low priority, with none currently considered sufficiently conserved. Geographic hotspots for species diversity, especially in the northern coastal areas, represent particularly high value regions for efficient further collecting for ex situ conservation and for in situ protection in Tunisia. N. Mezghani, National Genebank of Tunisia, Boulvard leader Yasser Arafat, ZI Charguia 1, 1080, Tunis, Tunisia; C.K. Khoury and D. Carver, USDA-ARS, National Lab. for Genetic Resources Preservation, 1111 South Mason St., Fort Collins, CO 80521, USA; C.K. Khoury and H.A. Achicanoy, International Center for Tropical Agriculture (CIAT), Km 17, Recta Cali-Palmira, Apartado Aéreo 6713, 763537 Cali, Colombia; D. Carver, Natural Resource Ecology Lab. , Colorado State Univ., Fort Collins, CO 80524-1499, USA; P. Simon and D. Spooner, USDAARS, Dep. of Horticulture, Univ. of Wisconsin-Madison, 1575 Linden Dr., Madison, WI 53706, USA; F. Martínez Flores, Dep. de Ciencias Ambientales y Recursos Naturales and Centro Iberoamericano de la Biodiversidad, Univ. de Alicante, PO Box 99, ES-03080 Alicante, Spain. Received 22 May 2019. Accepted 16 Aug. 2019. *Corresponding author (c.khoury@cgiar.org). Assigned to Associate Editor Tara Moreau. Abbreviations: ASD15, the proportion of the potential distribution model with a standard deviation above 0.15; AUC, area under the receiver operating characteristic curve; cAUC, calibrated area under the receiver operating characteristic curve; CSI, Consortium for Spatial Information; ERSex, ecological representativeness score ex situ; ERSin, ecological representativeness score in situ; FCSex, final conservation score ex situ; FCSin, final conservation score in situ; FCS-mean, final conservation score combined (both ex situ and in situ); G, genebank conservation record; GBIF, Global Biodiversity Information Facility; GBS, genotyping-by-sequencing; GRIN, Germplasm Resource Information Network; GRSex, geographic representativeness score ex situ; GRSin, geographic representativeness score in situ; H, herbarium reference record; NGS, next-generation sequencing; NPGS, National Plant Germplasm System; PCA, principal component analysis; SRS, sampling representativeness score; STAUC, standard deviation of the area under the receiver operating characteristic curve across replicates; WIEWS, World Information and Early Warning System on Plant Genetic Resources for Food and Agriculture. Published in Crop Sci. 59:2317–2328 (2019). doi: 10.2135/cropsci2019.05. 0333 © 2019 The Author(s). This is an open access article distributed under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Published September 26, 2019