Research Gaps and Challenges in the Conservation and Use of North American Wild Lettuce Germplasm

Abstract

The North American crop wild relatives (CWR) of lettuce (Lactuca L.) represent an underexplored pool of genetic diversity of potential value to breeding programs. The 10 species belong to three different groups: a native clade including at least six allotetraploid species [L. biennis (Moench) Fernald, L. canadensis L., L. floridana (L.) Gaertn., L. graminifolia Michx., L. hirsuta Muhl. ex Nutt., and L. ludoviciana (Nutt.) Riddell], a diploid clade with one species [L. tatarica (L.) C. A. Mey. subsp. pulchella (Pursh) Stebbins], and a clade related to the cultivated taxon (L. sativa L.) with three non-native species (L. saligna L., L. serriola L., and L. virosa L.). In this review, we examine the role of herbarium and genebank holdings in taxonomic and other foundational studies, as well as for germplasm exploration and use. We compile the state of knowledge on the ranges of lettuce CWR in North America, modeling the potential distributions of the species and assessing their ex situ and (for native species) in situ conservation status. We categorize seven of the species as high priority for further conservation and three as medium priority, with none currently considered low priority or sufficiently conserved. Further, we review morphological, phenological, genetic diversity, and pest and disease information with regard to North American species. We conclude by outlining the critical gaps and describing a way forward for addressing challenges in the conservation and use of North American wild lettuce germplasm. A. Lebeda*, E. Křístková, M. Kitner, and Ľ. Majeský, Dep. of Botany, Faculty of Science, Palacký Univ. in Olomouc, 78371 Olomouc, Czech Republic; I. Doležalová, Crop Research Institute, Centre of the Region Hana for Biotechnological and Agricultural Research, Šlechtitelů 29, 78371 Olomouc, Czech Republic; C.K. Khoury and D. Carver, USDA-ARS, National Laboratory for Genetic Resources Preservation, 1111 South Mason St., Fort Collins, CO, 80521, USA; C.K. Khoury, H.A. Achicanoy, and C.C. Sosa, International Center for Tropical Agriculture (CIAT), Km 17, Recta Cali-Palmira, Apartado Aéreo 6713, 763537 Cali, Colombia; M.P. Widrlechner, Departments of Horticulture and of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA 50011, USA; J. Hu, USDA-ARS, Washington State University, Pullman, WA 99164-6402, USA; D. Carver, Natural Resource Ecology Laboratory, Colorado State Univ., Fort Collins, CO 80524-1499, USA; C.C. Sosa, Grupo de investigación en Evolución, Ecología y Conservación EECO, Programa de Biología, Facultad de Ciencias Básicas y Tecnologías, Universidad del Quindío, Armenia, Colombia. Received 31 May 2019. Accepted 4 Oct. 2019. Assigned to Associate Editor Jorge da Silva.*Corresponding author ([email protected]). Abbreviations: AFLP, amplified fragment length polymorphism; CA50, circular area of 50-km radius; CGN, Centre for Genetic Resources, the Netherlands; CWR, crop wild relatives; ERSex, ecological representativeness score ex situ; ERSin, ecological representativeness score in situ; FCSc-mean, final combined conservation score (mean); FCSex, final conservation score ex situ; FCSin, final conservation score in situ; GBIF, Global Biodiversity Information Facility; GISH, genomic in situ hybridization; GRIN, Germplasm Resources Information Network; GRSex, geographical representativeness score ex situ; GRSin, geographical representativeness score in situ; IPK, Leibniz Institute of Plant Genetics and Crop Plant Research; ITS, internal transcribed spacer; LGCS, USDA Lactuca Germplasm Collection—Salinas; LGRCD, Lactuca Genetic Resources Collection, University of California, Davis; NPGS, US National Plant Germplasm System; PGRC, Plant Gene Resources of Canada; SRS, sampling representativeness score; SSR, simple sequence repeat; WIEWS, World Information and Early Warning System on Plant Genetic Resources for Food and Agriculture; WRPIS, Western Regional Plant Introduction Station. Published in Crop Sci. 59:2337–2356 (2019). doi: 10.2135/cropsci2019.05.0350 © 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/).