Crop wild relative

A crop wild relative (CWR) is a wild plant closely related to a domesticated plant. It may be a wild ancestor of the domesticated (cultivated) plant, or another closely related taxon.

Wild emmer wheat (Triticum dicoccoides), a CWR of cultivated wheats (Triticum spp), can be found in northern Israel.
Two conservationists collecting indigenous knowledge on cultural practices that favour CWR populations, from a farmer near Fes, Morocco.

Overview

The wild relatives of crop plants constitute an increasingly important resource for improving agricultural production and for maintaining sustainable agro-ecosystems. Their natural selection in the wild accumulates a rich set of useful traits that can be introduced into crop plants by crossing.[1][2][3] With the advent of anthropogenic climate change and greater ecosystem instability CWRs are likely to prove a critical resource in ensuring food security for the new millennium.[4] It was Nikolai Vavilov, the Russian botanist who first realized the importance of crop wild relatives in the early 20th century.[5] Genetic material from CWRs has been utilized by humans for thousands of years to improve the quality and yield of crops. Farmers have used traditional breeding methods for millennia, wild maize (Zea mexicana) is routinely grown alongside maize to promote natural crossing and improve yields. More recently, plant breeders have utilised CWR genes to improve a wide range of crops like rice (Oryza sativa), tomato (Solanum lycopersicum) and grain legumes.[6]

CWRs have contributed many useful genes to crop plants, and modern varieties of most major crops now contain genes from their wild relatives.[7] Therefore, CWRs are wild plants related to socio-economically important species including food, fodder and forage crops, medicinal plants, condiments, ornamental, and forestry species, as well as plants used for industrial purposes, such as oils and fibres, and to which they can contribute beneficial traits. A CWR can be defined as "... a wild plant taxon that has an indirect use derived from its relatively close genetic relationship to a crop...”[8]

Conservation of crop wild relatives
Example of one of the first genetic reserves established to conserve CWRs near Kalakh al Hosn, Syria

CWRs are essential components of natural and agricultural ecosystems and hence are indispensable for maintaining ecosystem health.[4] Their conservation and sustainable use is very important for improving agricultural production, increasing food security, and maintaining a healthy environment.[9][10][11]

Geographic hotspots of distributions of crop wild relatives not represented in genebanks

The natural populations of many CWRs are increasingly at risk. They are threatened by habitat loss through the destruction and degradation of natural environment or their conversion to other uses. Deforestation is leading to the loss of many populations of important wild relatives of fruit, nut, and industrial crops. Populations of wild relatives of cereal crops that occur in arid or semi-arid lands are being severely reduced by over grazing and resulting desertification. The growing industrialization of agriculture is drastically reducing the occurrence of CWRs within the traditional agro-ecosystems. The wise conservation and use of CWRs are essential elements for increasing food security, eliminating poverty, and maintaining the environment.[12]

Conservation strategies for CWRs often consider both in situ and ex situ conservation.[13][14] These are complementary approaches to CWR conservation, since each has its own advantages and disadvantages. For example, whilst ex situ conservation protects CWR (or more correctly, their genes) from threats in the wild, it can limit evolution and adaptation to new environmental challenges.

In 2016, 29% of wild relative plant species were completely missing from the world’s genebanks, with a further 24% represented by fewer than 10 samples. Over 70% of all crop wild relative species worldwide were in urgent need of further collecting to improve their representation in genebanks, and over 95% were insufficiently represented with regard to the full range of geographic and ecological variation in their native distributions. While the most critical priorities for further collecting were found in the Mediterranean and Near East, Western and Southern Europe, Southeast and East Asia, and South America, crop wild relatives insufficiently represented in genebanks are distributed across almost all countries worldwide.[15][16][14] A 2020 study found that 93.3% of wild relatives native to the United States are poorly represented in ex situ conservation repositories, while 93.1% are inadequately conserved in their natural habitats[17]

Examples of wild relatives

Grains

Vegetables

Note: Many different vegetables share one common ancestor, particularly in the Brassica family and plants. Many vegetables are also hybrids of different species, again this is particularly true of Brassicas.

Fruits

Oilseeds

Pulses

Tubers

See also

References
  1. Bioversity International, (2006). Crop wild relatives. Bioversity International, Rome.
  2. FAO, (1998). The State of the World’s Plant Genetic Resources for Food and Agriculture. FAO, Rome
  3. FAO, (2008). Establishment of a global network for the in situ conservation of crop wild relatives: status and needs. FAO, Rome
  4. Maxted N, Ford-Lloyd BV, Kell SP (2008). "Crop wild relatives: establishing the context.". In Maxted N, Ford-Lloyd BV, Kell SP, Iriondo J, Dulloo E, Turok J (eds.). Crop Wild Relative Conservation and Use. Wallingford: CABI Publishing. pp. 3–30.
  5. Vavilov NI (1926). Studies in the origin of cultivated plants. Leningrad: Institute of Applied Botany and Plant Breeding.
  6. Hajjar R, Hodgkin T (2007). "The use of wild relatives in crop improvement: a survey of developments over the last 20 years". Euphytica. 156 (1–2): 1–13. doi:10.1007/s10681-007-9363-0. S2CID 36269581.
  7. Dempewolf H, Baute G, Anderson J, Kilian B, Smith C, Guarino L (2017-05-06). "Past and Future Use of Wild Relatives in Crop Breeding". Crop Science. 57 (3): 1070–1082. doi:10.2135/cropsci2016.10.0885. ISSN 0011-183X.
  8. Maxted N, Ford-Lloyd BV, Jury SL, Kell SP, Scholten MA (2006). "Towards a definition of a crop wild relative". Biodiversity and Conservation. 15 (8): 2673–2685. doi:10.1007/s10531-005-5409-6. S2CID 26885014.
  9. Hawkes JG, Maxted N, Ford-Lloyd BV (2000). The ex situ conservation of plant genetic resources. Dordrecht: Kluwer. pp. 1–250.
  10. Heywood VH, Dulloo ME (2006). "In Situ Conservation of Wild Plant Species – a Critical Global Review of Good Practices. IPGRI Technical Bulletin No. 11. IPGRI, Rome". Cite journal requires |journal= (help)
  11. Meilleur BA, Hodgkin T (2004). "In situ conservation of crop wild relatives: Status and trends". Biodiversity and Conservation. 13 (4): 663–684. doi:10.1023/b:bioc.0000011719.03230.17. S2CID 3064850.
  12. Tanksley SD, McCouch SR (August 1997). "Seed banks and molecular maps: unlocking genetic potential from the wild". Science. 277 (5329): 1063–6. doi:10.1126/science.277.5329.1063. PMID 9262467.
  13. Khoury CK, Heider B, Castañeda-Álvarez NP, Achicanoy HA, Sosa CC, Miller RE, et al. (2015-04-21). "Distributions, ex situ conservation priorities, and genetic resource potential of crop wild relatives of sweetpotato [Ipomoea batatas (L.) Lam., I. series Batatas]". Frontiers in Plant Science. 6: 251. doi:10.3389/fpls.2015.00251. PMC 4404978. PMID 25954286.
  14. Taylor NG, Kell SP, Holubec V, Parra-Quijano M, Maxted N (2017). "A systematic conservation strategy for crop wild relatives in the Czech Republic" (PDF). Diversity and Distributions. 23 (4): 448–462. doi:10.1111/ddi.12539.
  15. Castañeda-Álvarez NP, Khoury CK, Achicanoy HA, Bernau V, Dempewolf H, Eastwood RJ, et al. (March 2016). "Global conservation priorities for crop wild relatives". Nature Plants. 2 (4): 16022. doi:10.1038/nplants.2016.22. PMID 27249561. S2CID 7174536.
  16. Khoury CK, Castañeda-Álvarez NP, Dempewolf H, Eastwood RJ, Guarino L, Jarvis A, Struik PC (2016). "Measuring the state of conservation of crop diversity: a baseline for marking progress toward biodiversity conservation and sustainable development goals". Crop Wild Relatives Policy Brief: 6. hdl:10568/74483.
  17. Khoury, Colin K.; Carver, Daniel; Greene, Stephanie L.; Williams, Karen A.; Achicanoy, Harold A.; Schori, Melanie; León, Blanca; Wiersema, John H.; Frances, Anne (2020-12-10). "Crop wild relatives of the United States require urgent conservation action". Proceedings of the National Academy of Sciences. doi:10.1073/pnas.2007029117. ISSN 0027-8424. PMID 33318205.
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