Horticulture Publications Horticulture 2019 Wild Lactuca Species in North America A. Lebeda Palacký University E. Křístková Palacký University I. Doležalová Medicinal and Special Plants of Crop Research Institute in Olomouc M. Kitner Palacký University Mark P. Widrlechner Iowa State University, [email protected] Follow this and additional works at: https://lib.dr.iastate.edu/hort_pubs Part of the Agricultural Science Commons, Ecology and Evolutionary Biology Commons, Horticulture Commons, Natural Resources and Conservation Commons, and the Plant Breeding and Genetics Commons The complete bibliographic information for this item can be found at https://lib.dr.iastate.edu/ hort_pubs/39. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Book Chapter is brought to you for free and open access by the Horticulture at Iowa State University Digital Repository. It has been accepted for inclusion in Horticulture Publications by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Wild Lactuca Species in North America Abstract This chapter presents a brief history of the uses of lettuce (Lactuca sativa L.) and its wild North American relatives, and reviews the agricultural importance of lettuce and challenges in its cultivation, in relation to nutritional quality, diseases, pests, and edaphic and climatic limitations. The evolution and taxonomy of the genus Lactuca are presented, with a primary focus on the wild Lactuca species of North America, their characterization, biogeography and distribution, habitat ecology, and genepools. Specific examples of phenotypic variability, genetic diversity and disease resistance of wild Lactuca taxa from both published reports and recent evaluations conducted in our laboratory are also presented. The past (and future) exploitation of wild Lactuca relatives in lettuce breeding is examined and discussed in the broader context of crop improvement. The current status of in situ and ex situ conservation of wild and weedy North American Lactuca is reviewed, along with recommendations on how these genetic resources could be better conserved and utilized. Keywords Wild lettuce, Genetic resosurce, Taxonomy, Biogeography, Genetic diversity, Conservation Disciplines Agricultural Science | Ecology and Evolutionary Biology | Horticulture | Natural Resources and Conservation | Plant Breeding and Genetics Comments This is a manuscript of a chapter published as Lebeda A., Křístková E., Doležalová I., Kitner M., Widrlechner M.P. (2019) Wild Lactuca Species in North America. In: Greene S., Williams K., Khoury C., Kantar M., Marek L. (eds) North American Crop Wild Relatives, Volume 2. Springer, Cham. doi: 10.1007/ 978-3-319-97121-6_5. Posted with permission. This book chapter is available at Iowa State University Digital Repository: https://lib.dr.iastate.edu/hort_pubs/39 Crop Wild Relatives and Wild Utilized Plants of North America (Springer Publishers, 2017) Part 3. Vegetables, Leafy Vegetables Chapter 16 Wild Lactuca Species in North America Lebeda A.1*, Křístková E.1, Doležalová I.2, Kitner M.1, Widrlechner M.P.3 1 Department of Botany, Faculty of Science, Palacký University in Olomouc, Czech Republic (* corresponding author: [email protected]) 2 Department of Genetic Resources for Vegetables, Medicinal and Special Plants of Crop Research Institute in Olomouc, Czech Republic 3 Departments of Horticulture and of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, Iowa, USA Abstract This chapter presents a brief history of the uses of lettuce (Lactuca sativa L.) and its wild North American relatives, and reviews the agricultural importance of lettuce and challenges in its cultivation, in relation to nutritional quality, diseases, pests, and edaphic and climatic limitations. The evolution and taxonomy of the genus Lactuca are presented, with a primary focus on the wild Lactuca species of North America, their characterization, biogeography and distribution, habitat ecology, and genepools. Specific examples of phenotypic variability, genetic diversity and disease resistance of wild Lactuca taxa from both published reports and recent evaluations conducted in our laboratory are also presented. The past (and future) exploitation of wild Lactuca relatives in lettuce breeding is examined and discussed in the broader context of crop improvement. The current status of in situ and ex situ conservation of wild and weedy North American Lactuca is reviewed, along with recommendations on how these genetic resources could be better conserved and utilized. 16.1 Introduction 16.1.1 Origin of the crop and brief history of use worldwide As one of the earliest domesticated vegetables (4000 - 8000 years BP), lettuce belongs to a core group of ancient crops (Hancock 2012). The center of diversity of related Lactuca species is in southwestern Asia (Kuang et al. 2008), with lettuce likely originating from this region (Zohary and Hopf 1993). The earliest known artifacts related to lettuce originate from the tomb decorations in Egypt’s Nile Valley. These decorations are similar to modern stalk or stem lettuce (Lebeda et al. 2007a). More recently, romaine lettuce probably arose in Italy in the 13th or 14th century. Head types of lettuce were noted for the first time in southern Europe in the 16th century (Lebeda et al. 2007a). Domesticated lettuce was probably brought to the Americas on the second voyage of Columbus in 1494 (Hedrick 1972). Lettuce (Lactuca sativa L.) is considered to be of polyphyletic origin and likely was selected from the genepool of L. serriola L. (Lebeda et al. 2007a; Kuang et al. 2008) (probably L. serriola f. integrifolia (Gray) S.D. Prince & R.N. Carter), followed by introgression of traits from other closely related Lactuca species (Lebeda et al. 2012b; Kitner et al. 2015) and similar DNA-sequence profiles, it is highly probable that some Lactuca species (L. azerbaijanica Rech. f., L. altaica Fisch. & C.A. Mey., L. aculeata Boiss. & Kotschy, and L. scarioloides Boiss.) 1 (Zohary 1991; Koopman et al. 1998) and probably also L. dregeana DC. (van Herwijnen and Manning, 2017) played important roles in the evolution of cultivated lettuce. The ongoing process of lettuce domestication (and breeding) is connected to the loss of typical features of wild Lactuca species. Systematic improvement and breeding of lettuce started in the second half of 19th century in Europe, and at the beginning of the 20th century in North America (Lebeda et al. 2007a; Mikel 2007). The most important modifications include the absence of leaf trichomes, changes in leaf shape and structure, the formation of heads, delayed bolting and flowering, a reduced content of latex and reduced bitterness (Lebeda et al. 2007a, 2009a). Recent breeding has been especially focused on leaf shape, shelf life, disease resistance, pest resistance, abiotic tolerance, nutritional quality, low nitrate content, and color variability (Lebeda et al. 2007a, 2009a, 2014). Various species of wild lettuce have been prized for medicinal and dietetic purposes by indigenous North American people (Borchers et al. 2000). For example, L. biennis (Moench) Fernald was used to ease lactation by the Ojibwa Indians (Smith 1932), and the latex of L. canadensis L. was used as phytotherapy for warts by the Ojibwa (Densmore 1928) and skin inflammation (including eczema) by the Menominee Indians (Lewis and Elvin-Lewis 2003). Native Americans used the roots of blue lettuce (L. tatarica (L.) C.A. Mey. subsp. pulchella (Pursh) Stebbins) as chewing gum (Reagan 1929); an infusion of it was made to treat diarrhea (Turner et al. 1980); and the young leaves were eaten as a green vegetable (Anonymous 2011), as were the leaves of L. canadensis (Hamel and Chiltoskey 1975) and L. ludoviciana (Nutt.) Riddell (Chamberlin 1911). In more recent times, an introduced species, opium or acrid lettuce (L. virosa L.) has been used by indigenous people for treating gastroenteritis (Hocking 1956) and for sedative purposes, especially for nervous complaints, but also as an aid in seeking meditative trances and visions (Anonymous 2016a). The health benefits of L. virosa tea have long been suspected (Anonymous 2016a). These examples, which are not meant to be exhaustive, demonstrate that wild Lactuca taxa have played an important role in the lives of the native peoples of North America, and suggest potential modern applications. 16.1.2 Modern day use Lettuce is one of the most important vegetable crops and the most popular leafy vegetable crop. It is almost exclusively used as a fresh, uncooked product with moderate dietetic value. Lettuce is diverse, occurring in at least seven distinct types (crisphead, cos (romaine), butterhead, leaf, latin, stem (stalk) and oilseed) (Lebeda et al. 2007a). However, recently new morphotypes (e.g., red leaf, baby lettuce) have been developed that do not fit into pre-existing categories. Currently, at least eight horticultural types divided on the basis of head shape and size, the shape, size and texture of the leaves, stem length, and seed size are under wide cultivation (Simko et al. 2014a,b). All these forms, except for two (stem and oilseed), are typically consumed raw (Rubatzky and Yamaguchi 1997; Welbaum 2015). Lettuce is produced on a commercial scale in many countries worldwide but is also frequently grown in small gardens. As a commercial crop, it is very important in Asia, North and Central America, and Europe (Lebeda et al. 2007a), and, recently, lettuce production been increasing in Australia (FAOSTAT 2016). About 80% of lettuce world production in 2011 (24.3 million tonnes) originated from four countries: China (52.3%), the United States (16%), India (4.4%), and Spain (3.6%) (Simko et al. 2014b; FAOSTAT 2013). In North America, lettuce production is concentrated in the United States, especially in California and Arizona, but there is also some production near Toronto and Montreal in Canada. In 2015, lettuce (head, leaf, and romaine) for fresh market was planted on ~100,000 ha in the United States, with a total production of 3,667,910 metric tons and a cash value of nearly $3 billion (USDA - NASS 2016).