Published online September 26, 2019 RESEARCH Distributions and Conservation Status of Carrot Wild Relatives in Tunisia: A Case Study in the Western Mediterranean Basin Najla Mezghani, Colin K. Khoury,* Daniel Carver, Harold A. Achicanoy, Philipp Simon, Fernando Martínez Flores, and David Spooner N. Mezghani, National Genebank of Tunisia, Boulvard leader Yasser ABSTRACT Arafat, ZI Charguia 1, 1080, Tunis, Tunisia; C.K. Khoury and D. Carver, Crop wild relatives, the wild progenitors and USDA-ARS, National Lab. for Genetic Resources Preservation, 1111 closely related cousins of cultivated plant South Mason St., Fort Collins, CO 80521, USA; C.K. Khoury and H.A. species, are sources of valuable genetic Achicanoy, International Center for Tropical Agriculture (CIAT), Km resources for crop improvement. Persisting gaps 17, Recta Cali-Palmira, Apartado Aéreo 6713, 763537 Cali, Colombia; in knowledge of taxonomy, distributions, and D. Carver, Natural Resource Ecology Lab., Colorado State Univ., Fort characterization for traits of interest constrain Collins, CO 80524-1499, USA; P. Simon and D. Spooner, USDA- their expanded use in plant breeding and ARS, Dep. of Horticulture, Univ. of Wisconsin-Madison, 1575 Linden likewise negatively affect ex situ (in genebanks) Dr., Madison, WI 53706, USA; F. Martínez Flores, Dep. de Ciencias and in situ (in natural habitats) conservation Ambientales y Recursos Naturales and Centro Iberoamericano de la planning. We compile the state of knowledge Biodiversidad, Univ. de Alicante, PO Box 99, ES-03080 Alicante, Spain. on the taxonomy and distributions of the wild Received 22 May 2019. Accepted 16 Aug. 2019. *Corresponding author relatives of carrot (genus Daucus L.) natively ([email protected]). Assigned to Associate Editor Tara Moreau. occurring within Tunisia—a hotspot of diversity Abbreviations: ASD15, the proportion of the potential distribution of the genus, containing 13 taxa (27% of species model with a standard deviation above 0.15; AUC, area under the receiver worldwide). We use ecogeographic informa- operating characteristic curve; cAUC, calibrated area under the receiver tion to characterize their potential adaptations operating characteristic curve; CSI, Consortium for Spatial Information; to abiotic stresses of interest in crop breeding ERSex, ecological representativeness score ex situ; ERSin, ecological and assess their ex situ and in situ conserva- representativeness score in situ; FCSex, final conservation score ex situ; tion status. We find substantial ecogeographic FCSin, final conservation score in situ; FCS-mean, final conservation score variation both across taxa and between popula- combined (both ex situ and in situ); G, genebank conservation record; GBIF, tions within taxa, with regard to adaptation to Global Biodiversity Information Facility; GBS, genotyping-by-sequencing; high temperatures, low precipitation, and other GRIN, Germplasm Resource Information Network; GRSex, geographic traits of potential interest. We categorize three representativeness score ex situ; GRSin, geographic representativeness of the taxa high priority for further conservation score in situ; H, herbarium reference record; NGS, next-generation both ex situ and in situ, five medium priority, and sequencing; NPGS, National Plant Germplasm System; PCA, principal five low priority, with none currently considered component analysis; SRS, sampling representativeness score; STAUC, sufficiently conserved. Geographic hotspots standard deviation of the area under the receiver operating characteristic for species diversity, especially in the northern curve across replicates; WIEWS, World Information and Early Warning coastal areas, represent particularly high value System on Plant Genetic Resources for Food and Agriculture. regions for efficient further collecting for ex situ conservation and for in situ protection in Tunisia. rop wild relatives—the wild progenitors and close rela- Ctives of cultivated plant species—have been the sources of a wide range of beneficial agronomic and quality traits used in Published in Crop Sci. 59:1–12 (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/). CROP SCIENCE WWW.CROPS.ORG 1 crop improvement (Dempewolf et al., 2017; Hajjar and al., 2014). Salinity tolerance during germination was found Hodgkin, 2007). As some populations of these wild plants in wild carrot seed from Pakistan and Turkey (Bolton are adapted to extreme climates, challenging soils, and and Simon, 2019). Heat tolerance during germination significant pests and diseases, they have substantial poten- was found in wild carrot seed from Pakistan, Portugal, tial to contribute to crop breeding for emerging and Tunisia, and Turkey (Bolton et al., 2019). projected future agricultural challenges (Dempewolf et Traits of interest found in other carrot wild relative al., 2014). taxa include carrot fly resistance in D. carota subsp. capil- Persisting gaps in knowledge of these plant genetic lifolius (Gilli) Arbizu and D. carota subsp. gummifer (Syme) resources constrain their use in plant breeding, including Hook. f. (Ellis, 1999; Ellis et al., 1993; Grzebelus et al., information on taxonomy, crossability, and gene pool clas- 2011; Simon 2000), cytoplasmic male sterility in D. carota sifications, distributions, and characterization for traits of subsp. gummifer, and salinity tolerance in D. carota subsp. interest (Dempewolf et al., 2017; Miller and Khoury, 2018). halophilus (Brot.) A. Pujadas (Tavares et al., 2010). Such foundational knowledge gaps also affect conservation The Apiaceae (Umbelliferae) family, with 466 genera efforts for the taxa, which are necessary to protect vulner- and 3820 species (Plunkett et al., 2019) is one of the largest able populations from habitat destruction, invasive species, families of seed plants. It is well supported as a monophy- climate change, and overharvesting in situ (Bellon et al., letic family and is well defined by a suite of morphological 2017; Brummitt et al., 2015; Jarvis et al., 2008a), as well as characters. However, generic circumscriptions within the to ensure that genetic resources are safeguarded for the long family have been the subject of long dispute, including term and are available for research in ex situ repositories for the genus Daucus (Plunkett and Downie, 1999). A (Castañeda-Álvarez et al., 2016; Gepts, 2006). genus-level treatment of Daucus by Sáenz Laín (1981) used Cultivated carrot [Daucus carota L. subsp. sativus morphological and anatomical data and recognized 20 (Hoffm.) Schübl. & G. Martens] is the most widely grown species. Rubatzky et al. (1999) later estimated 25 species. member of the Apiaceae and among the 10 most important The phylogenetic relationships among the species of vegetable crops, with global production on 1.2 million ha, Daucus and close relatives in the Apioideae have been clar- and a crop value of US$13.9 billion (2011–2015 average; ified by a series of molecular studies using DNA sequences FAO, 2019). Beyond its economic value, carrot is the of the plastid and nuclear genes as summarized in Spooner richest source of provitamin A carotenoids in the US diet, (2019). Of these recent studies, that by Banasiak et al. accounting for 45 to 50% of total intake (Simon et al., (2016) is taxonomically most significant in using a wide 2009). Micronutrient intake values for individual vegeta- range of Daucus in-groups and out-groups analyzed with bles are not available for the human population as a whole, DNA sequences from nuclear ribosomal internal tran- but per capita consumption of carrots in the United States scribed spacer (ITS) and three plastid markers. This study is similar to global per capita consumption (Simon, 2019) redefined and expanded the genus Daucus to include the indicating the important role of carrots as a source of following genera and species into its synonymy: Agrocharis dietary vitamin A globally. Hochst. (four species), Melanoselinum Hoffm. (one species), Wild carrot (D. carota L. subsp. carota) has played an Monizia Lowe (one species), Pachyctenium Maire & Pamp. important role in carrot breeding, as efficient hybrid carrot (one species), Pseudorlaya (Murb.) Murb. (two species), seed production depends on cytoplasmic male sterility, a Rouya Coincy (one species), Tornabenea Parl. (six species), maternally inherited trait that prevents the production Athamanta della-cellae E.A. Durand & Barratte, and Cryp- of viable pollen without affecting female fertility (Banga totaenia elegans Webb ex Bolle. Banasiak et al. (2016) et al., 1964). The predominant source of sterility used made the relevant nomenclatural transfers into Daucus today is petaloid cytoplasm discovered in two wild carrot and following this classification, the genus contains ?40 sources, first in New England by Henry Munger in 1953, species as well as an undetermined number of subspecies then in Wisconsin by Teddy Morelock in 1970 (reviewed in D. carota (Spooner et al., 2014). Relative to the present by Simon, 2000). Hybrid cultivars today account for study of Tunisia, Daucus now includes the former Pseudor- nearly all of the large-scale carrot production industry in laya pumila (L.) Grande [now Daucus pumilus (L.) Hoffmans North America, Europe, and Japan, so most of the carrots & Link] and the former Rouya polygama (Desf.) Coincy consumed in these markets have wild carrot cytoplasm. (now Daucus rouyi Spalik & Reduron). Despite