Lactuca serriola

Lactuca serriola, also called prickly lettuce,[2] milk thistle[2] (not to be confused with Silybum marianum, also called milk thistle), compass plant,[2] and scarole,[2] is an annual or biennial plant in the dandelion tribe within the daisy family. It has a slightly fetid odor and is commonly considered a weed of orchards, roadsides and field crops.[3] It is the closest wild relative of cultivated lettuce (Lactuca sativa L.).

Lactuca serriola
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Tribe: Cichorieae
Genus: Lactuca
Species:
L. serriola
Binomial name
Lactuca serriola
Synonyms[1]

Lactuca serriola is known as the compass plant because in the sun the upper leaves twist round to hold their margins upright.[4]

Lactuca serriola is native to Europe, Asia, and north Africa, and has become naturalized elsewhere.[2][5][6][7][8][9]

Description
note the clasping stem of the leaf
Close up of leaf showing fine spines

Lactuca serriola has a spineless reddish stem, containing a milky latex, growing up to 2 metres (6 ft 7 in).[10]

The leaves get progressively smaller as they reach its top. They are oblong or lanceolate, often pinnately lobed and (especially for the lower leaves), waxy grey green. Fine spines are present along the veins and leaf edges. The undersides have whitish veins. They emit latex when cut.

The flower heads are 1–1.5 cm (1⁄2–1⁄2 in) wide,[10] pale yellow, often tinged purple, with 12–20 ray flowers but no disc flowers. The bracts are also often tinged purple. It flowers from July until September in the northern hemisphere. The achenes are grey, tipped with bristles. The pappus is white with equal length hairs.[5][11]

Similar to Mycelis muralis but showing more than 5 florets.

It can cause pulmonary emphysema in cattle feeding exclusively on the plant.[12]

Culinary and medicinal uses

Lactuca serriola can be eaten as a salad, although it has something of a bitter taste. Young leaves can be eaten raw or cooked.[13] Older leaves can be steamed.[14] While unsubstantial, its roots have been used as a coffee substitute.[15]

Its presence in some ancient deposits has been linked more to its soporific properties which might suggest ritual use. The Ancient Greeks also believed its pungent juice to be a remedy against eye ulcers and Pythagoreans called the lettuce eunuch because it caused urination and relaxed sexual desire.[16] The Navajo used the plant as a ceremonial emetic.[17] In the island of Crete in Greece the leaves and the tender shoots of a variety called maroula (μαρούλα) or agriomaroulo (αγριομάρουλο) are eaten boiled.[18] It is used by a growing number of Jews and the Samaritans as the Maror (bitter herb) on Pesach.

Lactuca serriola contains lactucarium, which is the milky sap (white latex) that flows through the stem of the plant. It is used as a medicinal herb when dried after contact with air. Although the standard definition of lactucarium requires its production from Lactuca virosa, it was recognized that smaller quantities of lactucarium could be produced in a similar way from Lactuca sativa and Lactuca canadensis var. elongata, and even that lettuce-opium obtained from Lactuca serriola or Lactuca quercina was of superior quality.[19][20][21]

History
A cluster of nine L. serriola, growing to a height of 5.5 ft [1.7 m]

The Egyptian god Min is associated with this species of lettuce. Also, archaeobotanical evidence in Greek archaeological contexts is scanty, although uncarbonised seeds have been retrieved from a 7th-century BC deposit in a sanctuary of Hera on Samos. It is also described by Theophrastus. In mythology, Aphrodite is said to have laid Adonis in a lettuce bed, leading to the vegetable's association with food for the dead.[22]

Pathogen resistance

Lactuca serriola is the wild progenitor of cultivated lettuce (Lactuca sativa), and can be affected by lettuce downy mildew, one of the most serious diseases of lettuce.[23] L. serriola has shown resistance to the plant pathogen Bremia lactucae, the cause of the disease.[23] This pathogen is able to undergo sexual reproduction, and once virulent strains have been produced, can undergo rapid asexual reproductive cycles.[24] As a result, there are many strains, which vary in virulence.[24]

Resistance to Bremia lactucae in Lactuca serriola is due to Dm genes, or single dominant genes.[24] Nine of the dominant genes that confer resistance are Dml, Dm, Dm3, Dm6, Dml4, Dml5, DmlO, Dm5/8, Dm10, Dm4, Dm7, Dm11, and Dm13.[23] These genes are mapped in four linkage groups, so the genes within each group will be more likely to be inherited together.[23] Lactuca serriola and B. lactucae have a gene-for-gene relationship,[25] meaning that each resistance gene in the plant is associated with a specific gene in the pathogen, with avirulence being dominant to virulence.[23] The possible combinations of these Dm genes can provide the plant with resistance to multiple strains of Bremia lactucae.[23]

Testing for the presence of new resistance factors is conducted by screening samples of L. serriola with various isolates of B. lactucae.[23] Samples of L. serriola can be found around the world with genetic diversity between populations regarding the Dm genes.[26] This genetic diversity is considered a resource for lettuce breeding because it provides a greater variety of genes to be used in response to new strains of B. lactucae, which continually emerge.[23][26] There is especially high diversity within the Mediterranean area and Southwest Asia, but L. serriola has established populations on all continents and has the most widespread distribution compared to other Lactuca species.[26]

References
  1. "Lactuca serriola". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved April 2, 2012..
  2. "Lactuca serriola". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA). Retrieved December 17, 2017.
  3. Everitt, JH; Lonard, RL; Little, CR (2007). Weeds in South Texas and Northern Mexico. Lubbock: Texas Tech University Press. ISBN 978-0-89672-614-7.
  4. Blamey, Marjorie; Fitter, Richard; Fitter, Alistair (2003). Wild Flowers of Britain and Ireland. London: A&C Black. pp. 294–5. ISBN 0-7136-5944-0.
  5. Strother, John L. (2006). "Lactuca serriola". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). 19. New York and Oxford – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  6. Shi, Zhu; Kilian, Norbert. "Lactuca serriola". Flora of China. 20–21 – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  7. Flora Italiana, Lactuca serriola L. includes photos, drawings, European distribution map
  8. Cabrera, A. L. 1978. Compositae. 10: 1–726. In A. L. Cabrera (ed.) Flora de la provincia de Jujuy. Instituto Nacional de Tecnología Agropecuaria, Buenos Aires
  9. Atlas of Living Australia
  10. Elias, Thomas S.; Dykeman, Peter A. (2009) [1982]. Edible Wild Plants: A North American Field Guide to Over 200 Natural Foods. New York: Sterling. p. 104. ISBN 978-1-4027-6715-9. OCLC 244766414.
  11. Rose, Francis (1981). The Wild Flower Key. Frederick Warne & Co. pp. 390–391. ISBN 0-7232-2419-6.
  12. Common Weeds of the United States. New York: Dover. 1971. p. 426. ISBN 0-486-20504-5.
  13. "Lactuca serriola". Survival and Self Sufficiency. AU. Retrieved 9 September 2011.
  14. Nyerges, Christopher (2016). Foraging Wild Edible Plants of North America: More than 150 Delicious Recipes Using Nature's Edibles. Rowman & Littlefield. p. 188. ISBN 978-1-4930-1499-6.
  15. Nyerges, Christopher (2017). Foraging Washington: Finding, Identifying, and Preparing Edible Wild Foods. Guilford, CT: Falcon Guides. ISBN 978-1-4930-2534-3. OCLC 965922681.
  16. Detienne, Marcel (1977). The Gardens of Adonis: Spices in Greek Mythology. Translated by Lloyd, Janet. New Jersey: The Humanities Press. p. 125.
  17. "Lactuca serriola", Ethnobotany, U Mich.
  18. Stavridakis, Kleonikos G [Κλεόνικος Γ. Σταυριδάκης] (2006). Η Άγρια βρώσιμη χλωρίδα της Κρήτης [Wild edible plants of Crete]. Crete: Rethymnon. ISBN 960-631-179-1.
  19. Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D. (1898). "King's American Dispensary:Tinctura Lactucarii (U. S. P.)—Tincture of Lactucarium". Retrieved 2007-05-28.CS1 maint: multiple names: authors list (link)
  20. Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D. (1898). "King's American Dispensary:Lactuca.—Lettuce". Retrieved 2019-10-21.CS1 maint: multiple names: authors list (link)
  21. King; Felter; Lloyd, John; Harvey Wickes; John Uri (1898). King's American Dispensatory. Cincinnati: Ohio Valley Co. p. 1114–1117, see Lactuca.—Lettuce and Tinctura Lactucarii (U. S. P.)—Tincture of Lactucarium.CS1 maint: multiple names: authors list (link)
  22. Fragiska, M (2005), "Wild and Cultivated Vegetables, Herbs and Spices in Greek Antiquity", Environmental Archaeology, 10 (1): 73–82, doi:10.1179/146141005790083858.
  23. Beharav, A.; Lewinsohn, D.; Lebeda A.; Nevo, E. (2006). "New wild Lactuca genetic resources with resistance against Bremia lactucae". Genetic Resources and Crop Evolution. 53 (3): 467–474. doi:10.1007/s10722-004-1932-7. S2CID 279531.
  24. Maisonnueve, B; Bellec, Y; Anderson, P; Michelmore, R.W. (September 1994). "Rapid mapping of two genes for resistance to downy mildew from Lactuca serriola to existing clusters of resistance genes". Theoretical and Applied Genetics. 89 (1): 96–104. doi:10.1007/BF00226989. PMID 24177776. S2CID 12834976.
  25. Farrara, B. F.; Ilot, T. W.; Michelmore, R. W. (1987). "Genetic analysis of factors for resistance to downy mildew Bremia lactucae in species of lettuce Lactuca sativa and L. serriola". Plant Pathology. 36: 499–514. doi:10.1111/j.1365-3059.1987.tb02267.x.
  26. Sicard, D.; Woo, S. S.; Arroyo-Garcia, R.; Ochoa, O.; Nguyen, D.; Korol, A.; Nevo, E.; Michelmore, R. (1999). "Molecular diversity at the major cluster of disease resistance genes in cultivated and wild Lactuca spp". Theoretical and Applied Genetics. 99 (3–4): 405–418. doi:10.1007/s001220051251. PMID 22665172. S2CID 20828855.
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