Centres of origin and diversity of crop plants

Crop genetic diversity refers to the variety of genes and genotypes found in a particular crop species. Crop genetic diversity refers to the variety of genes and genotypes found in a particular crop species. It is essential It is essential to develop improved cultivars. to develop improved cultivars. To meet current and future breeding requirements. To meet current and future breeding requirements. If a crop species has large number of genetic variants it is said to be genetically diverse. If a crop species has large number of genetic variants it is said to be genetically diverse.

N.I Vavilov N.I Vavilov ( ) - realized the significance of genetic diversity for crop improvement. N.I Vavilov ( ) - realized the significance of genetic diversity for crop improvement. His team visited several countries and collected cultivated plants and their wild relatives His team visited several countries and collected cultivated plants and their wild relatives to use in the Russian breeding programme to develop varieties for various agroclimatic conditions of USSR. to use in the Russian breeding programme to develop varieties for various agroclimatic conditions of USSR. He proposed He proposed Main centres of diversity- 8 Main centres of diversity- 8 Secondary centres of diversity - 3 Secondary centres of diversity - 3

1 China 2 India 2a Indochina 3 Central Asia (N. India, Afghanistan, Turkmenistan) 4 The Near East 5 Mediterranean Sea, coastal and adjacent regions 6 Ethiopia 7 Southern Mexico and Middle America 8 Northeastern South America, Bolivia, Ecudor, Peru 8a Isle of Chile 1 China 2 India 2a Indochina 3 Central Asia (N. India, Afghanistan, Turkmenistan) 4 The Near East 5 Mediterranean Sea, coastal and adjacent regions 6 Ethiopia 7 Southern Mexico and Middle America 8 Northeastern South America, Bolivia, Ecudor, Peru 8a Isle of Chile

Centre of diversity (or) Vavilovian centers of diversity It refers to a place, region or area where maximum variability and diversity of crop plants is observed. It refers to a place, region or area where maximum variability and diversity of crop plants is observed. The centres of diversity were also considered as centres of origin of crop plants. The centres of diversity were also considered as centres of origin of crop plants. (1) Chinese Centre, (1) Chinese Centre, (2) India Centre, (2) India Centre, (2a) Indo-Malayan Centre, (2a) Indo-Malayan Centre, (3) Central Asiatic Centre, (3) Central Asiatic Centre, (4) The Asia Minor Centre (4) The Asia Minor Centre (5) Mediterranean Centre, (5) Mediterranean Centre, (6) Abyssinian Centre (6) Abyssinian Centre (7) South Mexican and Central American Centre, (7) South Mexican and Central American Centre, (8) South American Centre (8) South American Centre (8a) Chilean Centre, and (8a) Chilean Centre, and (8b) Brazilian- Paraguayan centre (8b) Brazilian- Paraguayan centre

Name of centre Main crops for which genetic diversity is found 1. Chinese Centre: It consists of the mountainous regions of central and western China and the neighbouring low lands. It is the largest and oldest independent center. Naked oat (SC), Soybean, Adzuki bean, Common bean (SC) Small Bamboo, Leaf Mustard (SC), Apricot, Peas, Orange, Sesame (SC), China tea, etc. 2. Indian Centre: This includes Burma, Assam, Malaya, Java Borneo,Sumatra and Philippines, but excludes North West India, Punjab and North Western Frontier Provinces. Rice, Chick pea, Moth Bean, Rice bean, Horse gram, Brinjal, Cucumber, Tree Cotton, Jute, Pepper, African Millet, Indigo, etc. 2(a) Indo-Malayan Centre Banana, Coconut, Yam and Pomelo

3. Central Asiatic Centre: It includes North West India, all of Afghanistan, the Soviet Republics of Tadjikistan and Tian Shan. It is also known as the Afghanistan center of origin. Bread wheat, Club wheat, Shot wheat, Rye (SC) Lentil, Chickpea, Sesame, Flax, Safflower, Carrot, Radish, Apple, Pear and Walnut 4. Asia Minor Centre: This is also known as the Near East or the Persian Centre of Origin. It includes the interior of Asia Minor, the whole of Transacaucasia, Iran and Highlands of Turkmenistan. Einkorn wheat, Durum wheat, Poulard wheat, Bread wheat, Two Rowed barley, Rye, Red oat, Chickpea (SC), lentil, pea (SC), Flex, Almond, Pomegranate, Pista, Apricot and Grape

5. Mediterranean Centre Durum wheat, Husked oats, Cabbage, Olive, Broad beans and Lettuce. 6. Abyssinian Centre: It includes Ethiopia and hill country of Eritrea. Durm wheat, Poulard wheat, Emmer wheat, Barley, Chickpea, Lentil, Pea, Flax, Sesame, Castor bean, African millet and Coffee 7. South Mexican and Central American Centre : This includes South Mexico and Central America. It is also referred to as the Mexican Centre of Origin. Maize, Common bean, Upland cotton, Pumpkin, Gourd, Squash, Sisal hemp and Pepper

8. South American Centre: This center includes the high mountainous regions of Peru, Bolivia, Ecuador, Colombia, parts of Chile, and Brazil and whole of Peraguay. Potao, Sweet potato, Lima bean, Tomato, Papaya, Tobacco and Sea Island cotton. 8(a) Chilean Centre Potato 8(b) Brazilian Paraguan Centre Peanut, Rubber Tree, Cocoa (SC), Pineapple, etc.

Deficiency… Vavilov could not adequately cover Africa. Vavilov could not adequately cover Africa. Australia was not at all covered. Australia was not at all covered. These two continents have tremendous wealth of crop genetic diversity of several crop plants. These two continents have tremendous wealth of crop genetic diversity of several crop plants. Difference between centre of origin and centre of diversity : Difference between centre of origin and centre of diversity : centre of origin of a crop species is generally confined to one place, centre of origin of a crop species is generally confined to one place, diversity of a crop may be found at more than one place. diversity of a crop may be found at more than one place.

Types of centres of diversity Two types: Two types: (1) primary centres of diversity (1) primary centres of diversity (2) secondary centres of diversity. (2) secondary centres of diversity.

Primary centres of diversity Primary centres Secondary centres Regions of vast genetic diversity of crop plants. These are original homes of the crop plants which are generally uncultivated areas like, mountains, hills, river valleys, forests, etc. Vavilov suggested that valuable forms of crop plants are found far away from their primary area of origin which he called secondary centres of origin or diversity. These are generally the cultivated areas.

Main features Primary centres Secondary centres wide genetic diversity wide genetic diversity Large number of dominant genes Large number of dominant genes Wild characters Wild characters Exhibit less crossing over Exhibit less crossing over Natural selection operates Natural selection operates Lesser genetic diversity Lesser genetic diversity Large number of recessive genes Large number of recessive genes Mostly desirable characters Mostly desirable characters Exhibit more crossing over Exhibit more crossing over Both natural and artificial selections operate Both natural and artificial selections operate

Micro centres In some cases, small areas within the centres of diversity exhibit tremendous genetic diversity of some crop plants. In some cases, small areas within the centres of diversity exhibit tremendous genetic diversity of some crop plants. These areas are referred to as microcentres. These areas are referred to as microcentres. Micro centres are important sources for collecting valuable plant forms and also for the study of evolution of cultivated species. Micro centres are important sources for collecting valuable plant forms and also for the study of evolution of cultivated species. Main features: Main features: They represent small areas within the centres of diversity They represent small areas within the centres of diversity Exhibit tremendous genetic diversity Exhibit tremendous genetic diversity The rate of natural evolution is faster than larger areas The rate of natural evolution is faster than larger areas They are important sites for the study of crop evolution They are important sites for the study of crop evolution

Vavilov also developed the concept of parallel series of variation or Law of homologous series of variation. Vavilov also developed the concept of parallel series of variation or Law of homologous series of variation. This concept states that a particular variation observed in a crop species is also expected to be available in its another related species. This concept states that a particular variation observed in a crop species is also expected to be available in its another related species. For instance, if we get dwarf collections in one crop species the same may be found in another related species also. For instance, if we get dwarf collections in one crop species the same may be found in another related species also.