1. Introduction
Agriculture transformed human societies. The domestication of wild plants and animals allowed humans to settle, create surplus food, and develop civilization. Each cultivated crop has a geographic story — regions where it was first domesticated and regions where the greatest genetic variability is preserved. These are known as centres of origin and centres of diversity. Understanding them is essential for plant breeding, conservation of genetic resources, and sustaining global food security.
2. Historical background & the need for the concept
In the early 20th century, botanists and plant explorers collected seed and recorded local crop forms across continents. The Russian geneticist Nikolai I. Vavilov synthesized this knowledge, proposing the idea of centres of origin — geographic regions that acted as the cradles of domesticated crops. Vavilov's work remains foundational; modern archaeology and molecular genetics have refined his ideas but broadly validate the usefulness of identifying geographic centres where domestication and high diversity occurred.
Historical note: Vavilov (1887–1943) organized global expeditions, assembled large seed collections, and proposed that the region showing maximum diversity was likely the origin of the crop. He established an influential seed bank in Leningrad.
3. Definitions and characteristics
3.1 Centre of Origin
A centre of origin is the geographical area where a crop was first domesticated from its wild relatives. Indicators include archaeological records of early cultivation, presence of wild progenitors, and the occurrence of primitive landraces.
3.2 Centre of Diversity
A centre of diversity is a region where a crop and its close relatives show a high degree of genetic variation. This is determined by the existence of numerous landraces, wild relatives, and locally adapted ecotypes. Centers of diversity are primary sources of useful genetic traits for plant breeding.
3.3 Practical differences
| Aspect | Centre of Origin | Centre of Diversity |
|---|---|---|
| Meaning | Historical domestication site | Region with maximum genetic variation |
| Evidence | Archaeology, wild progenitors | Landraces, gene pools, wild relatives |
| Time component | Linked to early human activity | Could be present-day accumulation |
| Use | Understanding domestication history | Breeding and conservation resource |
4. Vavilov's Centres of Origin (overview)
Vavilov proposed several primary centres (originally eight) where he observed maximum crop diversity. These centres correspond to regions with a long history of agriculture and many wild relatives of crops.
- Chinese Centre — rice, soybean, many millets, peach, apricot.
- Indo-Burma (Indian) Centre — rice, sugarcane, brinjal (eggplant), mango, citrus, black pepper.
- Central Asiatic Centre — apple, almond, onion, carrot, spinach.
- Near East / Fertile Crescent — wheat, barley, lentil, pea, chickpea, flax, grape, fig.
- Mediterranean Centre — olive, cabbage, lettuce, clover.
- Abyssinian (Ethiopian) Centre — coffee, castor, sorghum, finger millet, teff.
- Central American Centre — maize, common bean, cacao, chili, cotton.
- Andean / South American Centre — potato, cassava, tomato, groundnut, quinoa, tobacco.
5. Why centres of origin and diversity matter
The identification of these regions matters for several scientific and practical reasons:
- Genetic resource for breeding: Centres of diversity hold alleles for disease resistance, abiotic stress tolerance (drought, salinity, flood), and quality traits (nutrition, taste).
- Conservation: Protecting in-situ and ex-situ germplasm prevents irreversible loss of genetic variation.
- Understanding domestication: Archaeological and genetic studies of these regions reveal how crops evolved under human selection.
- Food security: Genetic variation is the raw material to adapt crops to changing climates and pests.
- Cultural heritage: Landraces are intertwined with local farming knowledge and cuisine.
6. Modern revisions and molecular evidence
Since Vavilov's time, archaeobotany, carbon-dating of plant remains, and molecular genetics (DNA markers, genome sequencing) have refined and sometimes revised where and how many times crops were domesticated. Two important modern findings are:
- Multiple domestication events: Some crops, such as rice and lentil, appear to have been domesticated independently in separate regions.
- Secondary centres: When crops spread to new regions they diversified further under new climates and human selection — creating secondary centres of diversity (for example, wheat in India).
These insights mean that the term "centre" can sometimes oversimplify a complex process involving many places and long time periods.
7. Examples — Crop-wise details
7.1 Rice (Oryza sativa)
Rice is a staple for more than half the world's population. Evidence suggests independent domestication in the Yangtze Valley (China) and the Ganges region (India). Wild relatives, numerous landraces adapted to upland, lowland, and tidal ecologies, and the crop's cultural centrality make its origin/diversity story complex.
7.2 Wheat (Triticum spp.)
Wheat's earliest domestication traces to the Fertile Crescent ~10,000 years ago. Wild einkorn and emmer wheats were among the first domesticated grasses. Wheat later spread to Europe, North Africa, and South Asia where breeders selected new forms and landraces.
7.3 Maize (Zea mays)
Maize was domesticated from the wild grass teosinte in southern Mexico about 9,000 years ago. From Mesoamerica it spread throughout the Americas and, after European contact, to Africa and Asia where new varieties emerged.
7.4 Potato (Solanum tuberosum)
Originating in the Andean highlands of South America, potato diversity is greatest in Peru and Bolivia. Indigenous farmers developed hundreds of landraces adapted to altitude, day-length, and soil types.
8. Conservation strategies
Preserving crop genetic resources follows two complementary approaches:
8.1 In situ conservation
Protecting crops and wild relatives in their natural habitats or within traditional farming systems maintains the evolutionary processes that generate diversity. Examples include community seed-saving programs and protected areas that conserve wild gene pools.
8.2 Ex situ conservation
Collecting and storing germplasm in seed banks, field gene banks, and cryopreservation facilities safeguards varieties that may be lost in nature. Notable examples include national genebanks and the Svalbard Global Seed Vault.
Link to policy: International agreements such as the FAO International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA) set frameworks for access and benefit-sharing of crop germplasm.
9. Case studies (concise)
9.1 Wheat rust resistance from the Fertile Crescent
Breeders have mined wild wheat relatives to find resistance genes against stem and stripe rust. These have been introgressed into modern cultivars, significantly reducing yield losses in affected regions.
9.2 Rice landraces and flood tolerance
Traditional rice varieties from flood-prone regions contain alleles for submergence tolerance. Such alleles have been used in breeding programs to develop varieties that survive prolonged flooding.
10. Challenges & threats
- Loss of habitat and wild relatives due to urbanization and land conversion.
- Genetic erosion from replacement of landraces by high-yielding uniform varieties.
- Climate change shifting habitats and altering evolutionary pressures.
- Underfunded conservation programs and gaps in international benefit-sharing mechanisms.
Mitigation requires local and global action: in-situ conservation by farmers, supported ex-situ collections, and policies that reward custodians of genetic diversity.
11. Summary
Centres of origin and diversity are foundational concepts in the study of crop evolution, breeding, and conservation. Vavilov's pioneering work identified geographic hotspots of diversity; modern genetics and archaeology have refined these ideas to reveal multiple domestication events and dynamic patterns of diversity. Protecting these centres is vital for future food security and sustainable agriculture.
12. Further reading and resources
- Vavilov NI. (1926). "Studies on the origin of cultivated plants."
- Food and Agriculture Organization (FAO) publications on plant genetic resources.
- International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA) — policy documents.
- Recent review articles in journals such as Trends in Plant Science, Nature Plants, and Annals of Botany.
