Center of origin of crop plants

plant resources and its utilization ( Center of origin of crop plants)

1. CENTRES OF ORIGIN & DIVERSITY OF CROP PLANTS Presented by- MOHD. SALIM 2018-BTM-28 DEPARTMENT OF BOTANY ALIGARH MUSLIM UNIVERSITY(ALIGARH )

2. INTRODUCTION CENTRES OF ORIGIN : A centres of origin is a geographical area where a group of organisms either domesticated or wild, first develop its distinctive properties. Centres of origin are also considered as centres of diversity. It has centres which explain and studied by NIKOLAI VAVILOV.

3. Nikolai Vavilov Based on genetics, chromosome studies and anatomical data. Vavilov concluded that the most likely areas of origin were, where the plants was cultivated and the wild ancestors grew. In 1926 he published “ Studies on the Origin of Cultivated P lants ” which described his theory on the origin of crops.

4. As far as can be seen from the literature, Vavilov considered that “as a rule the primary foci of crop origins were in mountainous regions, characterized by the presence of dominant alleles.” In his work entitled  The Phytogeographical Basis for Plant Breeding  (Vavilov 1935) he summarizes and pulls together all his previous work on centres of origin and diversity. In this he recognizes eight primary centres. Later subdivided into 11 in 1935.

5. VAVILOVIAN CENTRES

6. VAVILOVIAN CENTRES I. The Chinese centres   - in which he recognizes 138 distinct species of which probably the earlier and most important were cereals, buckwheats and legumes. II. The Indian centres   (including the entire subcontinent) - based originally on rice, millets and legumes, with a total of 117 species .

7. IIa. The Indo-Malayan centres  (including Indonesia, Philippines, etc.) - with root crops ( Dioscorea  spp.,  Tacca,  etc.) preponderant, also with fruit crops, sugarcane, spices, etc., some 55 species. III. The Inner Asiatic centres  (Tadjikistan, Uzbekistan, etc.) - with wheat, rye and many herbaceous legumes, as well as seed-sown root crops and fruits, some 42 species.

8. IV. Asia Minor  (including Transcaucasia, Iran and Turkmenistan) - with more wheats, rye, oats, seed and forage legumes, fruits, etc., some 83 species. V. The Mediterranean centres  - of more limited importance than the others to the east, but including wheats, barleys, forage plants, vegetables and fruits -especially also spices and ethereal oil plants, some 84 species.

9. VI. The Abyssinian  (now Ethiopian) centres - of lesser importance, mostly a refuge of crops from other regions, especially wheats and barleys, local grains, spices, etc., some 38 species. VII. The South Mexican and Central American centres  - important for maize,  Phaseolus  and Cucurbitaceous species, with spices, fruits and fibre plants, some 49 species.

10. VIII. South America Andes region  (Bolivia, Peru, Ecuador) - important for potatoes, other root crops, grain crops of the Andes, vegetables, spices and fruits, as well as drugs (cocaine, quinine, tobacco, etc.), some 45 species. VIIIa. The Chilean centres  - only four species - outside the main area of crop domestication, and one of these ( Solanum tuberosum ) derived from the Andean centres in any case. This could hardly be compared with the eight main centres. VIIIb. Brazilian-Paraguayan centres  - again outside the main centres with only 13 species, though  Manihot  (cassava) and  Arachis  (peanut) are of considerable importance; others such as pineapple,  Hevea  rubber,  Theobroma cacao  were probably domesticated much later.

11. TYPE OF CENTRES OF DIVERSITY T here are two types: 1. PRIMARY CENTRES OF DIVERSITY 2. SECONDARY CENTRES OF DIVERSITY

12. DIFFERENCES

13. MICRO CENTRES In some cases, small areas within the centres of diversity exhibit tremendous genetic diversity of some crop plants. These areas are refer to as micro centres. Micro centres are important sources for collecting valuable plants from and also for the study of evolution of cultivated species.

14. ALPHONSE DE CANDOLLE(1883) Wrote a book “ PHYTOGRAPHIE ” ON THE ORIGIN OF CULTIVATED PLANTS. Wild relatives of the major crops (rice, wheat, beans). French systematic botanist (taxonomist) proposed that the crops of the world originated in 3 centres : Mesoamerica The fertile crescent of the Middle East South East Asia

15. Criteria for recognizing centres of origin Places where a plant grows spontaneously in wild state. Places where fragments of plants in old deposits and buildings ( archeological and palaeobotanical) are found. Archives describing the adventures of travelers. Philogical (naming) origin.

16. CONCLUSION Wide range of plant diversity in the tropical and warm temperate regions of the world our major food crops have come mainly from high mountain valleys, isolated from each other to a large extent and with a very habitat range. People made selections of wheat, barley, oats, rye, potatoes, and maize which were eventually cultivated.

17. These plants were weeds or possessed the syndrome of not being able to compete well with climax vegetation hence they grew in areas where nature or humans had reduced competition from other species, were noticed, eaten re-sown by chance and eventually became domesticated. Several other weedy plants were never or only temporary domesticated, remaining as weeds but often hybridizing by chance with the cultivated ones and thus enhancing their diversity. It seems that the restricted access of the mountain valleys and the wide range of altitudes helped to produce and select the diversity needed for domestication.

18. REFRENCES ECONOMIC BOTANY IN THE TROPICS- S.L.KOCCHAR https://www.google.com/search?q=centres+OF+ORIGIN+OF+crop+plants&oq=centres&aqs=chrome.0.69i59j69i57j69i61l2j0l2.2698j0j7&sourceid=chrome&ie=UTF-8#