Vavilov’s centres of origin | Botany Optional for UPSC PDF Download

Introduction

The term "centre of origin" refers to a specific geographical area where a particular group of organisms, whether they are domesticated or wild, originally originated on Earth. While many have assumed that these centres of origin are also hubs of biodiversity, it's important to note that centres of diversity may not necessarily coincide with the origin of crop plants. Although a few species may have independently originated in multiple places, most species had their initial origin in a specific location and then spread to other regions. In simpler terms, a crop plant typically originates in one primary location, whereas centres of diversity may be scattered in multiple locations. Determining the exact origin of species is often speculative and relies on indirect evidence.
Understanding the origins of crop plants holds significance in the field of plant breeding as it helps locate wild relatives, related species, and new genetic traits. This knowledge is crucial for preventing genetic erosion, which occurs when germplasm is lost due to the disappearance of ecotypes and their natural habitats.
The Russian scientist Nikolai Ivanovich Vavilov and his colleagues conducted extensive research in various countries, collecting a vast array of crop plants and their wild counterparts. They utilized this collection in Russia's breeding programs to develop improved crop varieties. Vavilov's conclusions were based on evidence from various fields such as morphology, anatomy, cytology, genetics, plant geography, and distribution.
He posited that significant centres of origin were consistently situated in the lower mountainous and hilly regions of tropical and subtropical areas. Additionally, he identified secondary centres of origin where multiple species had crossed with one another. These secondary centres of origin represented places where natural and artificial selection processes occurred sequentially. Vavilov emphasized that the domestication of plants was not a random event but rather a continuous and deliberate process.

Vavilov's centers of origin

In 1926, he published his findings and developed a theory regarding the centres of origin of cultivated plants.
He proposed the existence of eight distinct centres of origin for crop plants, each characterized by specific details:

1. Chinese Centre: This is considered one of the earliest and largest independent centres of origin for cultivated plants. It encompasses the mountainous regions of central and western China. Some of the endemic species originating from this centre include soybean, radish, turnip, pear, peach, plum, Colocasia, buckwheat, opium poppy, eggplant, apricots, oranges, and Chinese tea, among others.
2. Himalayan Centre: Also known as the Indian centre of origin, this region includes areas in Assam, Burma, Indo-China, and the Malay Archipelago. Endemic species from this centre include rice, red gram, chickpea, cowpea, mung bean, eggplant, cucumber, sugarcane, black pepper, moth bean, rice bean, cotton, turmeric, indigo, and various millets.
3. Mediterranean Centre: Encompassing the regions bordering the Mediterranean Sea, this centre is the birthplace of many cultivated vegetables. Notable endemic species include durum wheat, emmer wheat, oat, barley, lentil, pea, grass pea, broad bean, cabbage, asparagus, peppermint, and more.
4. Abyssinian Centre: This area comprises Ethiopia and parts of Somalia. Endemic species originating from this centre include wheat, sorghum, pearl millet, safflower, castor, broad bean, okra, and coffee.
5. Central Asian Centre: Encompassing north-western India, Afghanistan, Uzbekistan, and western China, this centre gave rise to endemic species like bread wheat, club wheat, sesame, linseed, muskmelon, carrot, onion, garlic, apricot, grape, hemp, and cotton.
6. Asia Minor Centre: Covering regions in Near East Asia such as Iran and Turkmenistan, this centre's endemic species include wheat, rye, pomegranate, almond, fig, cherry, walnut, alfalfa, Persian clover, and more.
7. Central American Centre: This centre includes the southern parts of Mexico, Costa Rica, Guatemala, and Honduras. It gave rise to endemic species like maize, kidney bean, lima bean, melon, pumpkin, sweet potato, arrowroot, chili peppers, cotton, papaya, guava, and avocado.
8. South American Centre: Encompassing regions in Peru, the islands of southern Chile, Brazil, and Paraguay, this centre is the origin of species such as potatoes, sweet potatoes, lima beans, tomatoes, papayas, tobacco, quinine, cassava, rubber, peanuts, cocoa, pineapples, and more.

Limitations of Vavilov's views

Our expanding knowledge of cultivated plants has led to certain modifications in Vavilov's views, as they have revealed limitations in his perspective:

• Vavilov originally considered the region with the greatest genetic diversity of a species as its centre of origin. However, it is now known that for many species, their centres of origin and genetic diversity do not necessarily coincide. For instance, this is the case with maize and tomatoes.
• Vavilov's theory posited that the centres of origin of cultivated plants were predominantly located in mountainous and hilly areas within tropical and sub-tropical regions. Recent evidence suggests that many cultivated plants also have their origins in plains.
• Today, we have identified several crops whose centres of origin differ from those suggested by Vavilov. Additionally, there are instances where more than one centre of origin exists. Furthermore, the origins of many species remain untraceable due to a lack of sufficient evidence.
• Vavilov's concept that the primary centre is characterized by a high frequency of dominant alleles toward the centre and recessive alleles toward the periphery is no longer considered acceptable based on the latest scientific knowledge.