Crop Improvement – I (Kharif)
Part A.
Centres of origin
The center of origin is a term used to refer to the geographic region where a particular group of plants first evolved. It is also known as the "primary center of diversity" or the "primary center of domestication."
The concept of the center of origin was first proposed by Russian botanist Nikolai Vavilov in the 1920s. He traveled extensively around the world, collecting and studying plant specimens, and identified several centers of origin for important food crops, such as wheat, corn, and potatoes.
The idea behind the center of origin is that the environmental conditions in a particular region were favorable for the evolution or domestication of a particular species. This region may have provided the ideal combination of soil, climate, and other factors that allowed the species to thrive and adapt to its surroundings.
Understanding the center of origin of a particular plant species is important for conservation efforts, as well as for agricultural purposes. It can help scientists and farmers identify the genetic diversity that exists within a species, which can be used to develop more resilient and productive varieties. Additionally, it can inform efforts to protect and preserve the natural habitats where these species originated, in order to maintain the rich biodiversity of our planet.
The center of origin of a particular species is not always the same as the place where it is currently found in the wild. This is because environmental conditions may have changed over time, or the species may have been introduced to new regions by humans. For example, the center of origin of the apple is believed to be in the mountains of Kazakhstan, but apples are now grown in many parts of the world.
Plant breeding now relies on crop plant origin to find wild relatives, related species, and new genes (especially dominant genes, sources of disease resistance). Knowledge of crop plant origins is critical for avoiding genetic erosion, germplasm loss due to the loss of ecotypes and landraces, habitat loss (such as rainforests), and increased urbanisation. Germplasm preservation is accomplished through gene banks (primarily seed collections, but now frozen stem sections) and natural habitat preservation (especially in centres of origin).
Vavilov proposed eight main diversity centres and three subsidiary diversity centres. N.I. Vavilov introduced the concept of centres of origin in 1926. He identified eight major diversity centres and three sub-centres. He proposed the parallel variation law.
Law of Parallel variation: N.I. Vavilov (1951) developed the concept of parallel variation or the law of homologous series of variations based on his study of crop diversity and centres of origin. Vavilov used the principle of homologous series of variations as a clue for discovering similar characters in related species.
The Eight Vavilovian Centers: Old World
I. Chinese Center: The largest independent centre, encompassing central and western China's mountainous regions and adjacent lowlands. There are a total of 136 endemic plants listed, with a few of them known to us as important crops.
Cereals and Legumes
- Broomcorn millet, Panicum miliaceum
- Italian millet, Panicum italicum
- Japanese barnyard millet, Panicum frumentaceum
- Kaoliang, Andropogon sorghum
- Buckwheat, Fagopyrum esculentum
- Hull-less barley, Hordeum hexastichum
- Soybean, Glycine max
- Adzuki bean, Phaseolus angularis
- Velvet bean, Stizolobium hassjoo
Roots, Tubers, and Vegetables
- Chinese yam, Dioscorea batatas
- Radish, Raphanus sativus
- Chinese cabbage, Brassica chinensis, B. pekinensis
- Onion, Allium chinense, A. fistulosum, A. pekinense
- Cucumber, Cucumis sativus
Fruits and Nuts
- Pear, Pyrus serotina, P. ussuriensis
- Chinese apple, Malus asiatica
- Peach, Prunus persica
- Apricot, Prunus armeniaca
- Cherry, Prunus pseudocerasus
- Walnut, Juglans sinensis
- Litchi, Litchi chinensis
Sugar, Drug, and Fiber Plants
- Sugarcane, Saccharum sinense
- Opium poppy, Papaver somniferum
- Ginseng, Panax ginseng
- Camphor, Cinnamomum camphora
- Hemp, Cannabis sativa
II. Indian Center: This area has two subcenters.
A. Main Center (Hindustan): Assam and Burma are included, but not Northwest India, Punjab, or the Northwest Frontier Provinces. 117 plants were considered endemic in this area.
Cereals and Legumes
- Rice, Oryza sativa
- Chickpea or gram, Cicer arietinum
- Pigeon pea, Cajanus indicus
- Urd bean, Phaseolus mungo
- Mung bean, Phaseolus aureus
- Rice bean, Phaseolus calcaratus
- Cowpea, Vigna sinensis
Vegetables and Tubers
- Eggplant, Solanum melongena
- Cucumber, Cucumis sativus
- Radish, Raphanus caudatus (pods eaten)
- Taro, Colocasia antiquorum
- Yam, Dioscorea alata
Fruits
- Mango, Mangifera indica
- Orange, Citrus sinensis
- Tangerine, Citrus nobilis
- Citron, Citrus medica
- Tamarind, Tamarindus indica
Sugar, Oil, and Fiber Plants
- Sugar cane, Saccharum officinarum
- Coconut palm, Cocos nucifera
- Sesame, Sesamum indicum
- Safflower, Carthamus tinctorius
- Tree cotton, Gossypium arboreum
- Oriental cotton, Gossypium nanking
- Jute, Corchorus capsularis
- Crotalaria, Crotalaria juncea
- Kenaf, Hibiscus cannabinus
Spices, Stimulants, Dyes, and Miscellaneous
- Hemp, Cannabis indica
- Black pepper, Piper nigrum
- Gum arabic, Acacia arabica
- Sandalwood, Santalum album
- Indigo, Indigofera tinctoria
- Cinnamon tree, Cinnamomum zeylanticum
- Croton, Croton tiglium
- Bamboo, Bambusa tulda
B. Indo-Malayan Center: Includes Indo-China and the Malay Archipelago. Fifty-five plants were listed, including:
Cereals and Legumes
- Job’s tears, Coix lacryma
- Velvet bean, Mucuna utilis
Fruits
- Pummelo, Citrus grandis
- Banana, Musa cavendishii, M. paradisiaca, H. sapientum
- Breadfruit, Artocarpus communis
- Mangosteen, Garcinia mangostana
Oil, Sugar, Spice, and Fiber Plants
- Candlenut, Aleurites moluccana
- Coconut palm, Cocos nucifera
- Sugarcane, Saccharum officinarum
- Clove, Caryophyllus aromaticus
- Nutmeg, Myristaca fragrans
- Black pepper, Piper nigrum
- Manila hemp or abaca, Musa textilis
III. Central Asiatic Center: Northwest India (Punjab, Northwest Frontier Provinces, and Kashmir), Afghanistan, Tajikistan, Uzbekistan, and western Tian-Shan comprise the Central Asiatic Center. This centre's plant list includes 43 different types of wheat.
Grains and Legumes
- Common wheat, Triticum vulgare
- Club wheat, Triticum compactum
- Shot wheat, Triticum sphaerocoecum
- Pea, Pisum sativum
- Lentil, Lens esculenta
- Horse bean, Vicia faba
- Chickpea, Cicer arientinum
- Mung bean, Phaseolus aureus
- Mustard, Brassica juncea
- Flax, Linum usitatissimum (one of the centers)
- Sesame, Sesamum indicum
Fibre Plants
- Hemp, Cannabis indica
- Cotton, Gossypium herbaceum
Vegetables
- Onion, Allium cepa
- Garlic, Allium sativum
- Spinach, Spinacia oleracea
- Carrot, Daucus carota
Fruits
- Pistacia, Pistacia vera
- Pear, Pyrus communis
- Almond, Amygdalus communis
- Grape, Vitis vinifera
- Apple, Malus pumila
IV. Near-Eastern Center: Includes the interior of Asia Minor, all of Transcaucasia, Iran, and the highlands of Turkmenistan. Eighty-three species including nine species of wheat were located in this region.
Grains and Legumes
- Einkorn wheat, Triticum monococcum (14 chromosomes)
- Durum wheat, Triticum durum (28 chromosomes)
- Poulard wheat, Triticum turgidum (28 chromosomes)
- Common wheat, Triticum vulgare (42 chromosomes)
- Oriental wheat, Triticum orientale
- Persian wheat, Triticum persicum (28 chromosomes)
- Triticum timopheevi (28 chromosomes)
- Triticum macha (42 chromosomes)
- Triticum vavilovianum, branched (42 chromosomes)
- Two-row barleys, Hordeum distichum, H. nutans
- Rye, Secale cereale
- Mediterranean oats, Avena byzantina
- Common oats, Avena sativa
- Lentil, Lens esculenta
- Lupine, Lupinus pilosus, L. albus
Forage Plants
- Alfalfa, Medicago sativa
- Persian clover, Trifolium resupinatum
- Fenugreek, Trigonella foenum graecum
- Vetch, Vicia sativa
- Hairy vetch, Vicia villosa
Fruits
- Fig, Ficus carica
- Pomegranate, Punica granatum
- Apple, Malus pumilo (one of the centers)
- Pear, Pyrus communis and others
- Quince, Cydonia oblonga
- Cherry, Prunus cerasus
- Hawthorn, Crataegus azarolus
V. Mediterranean Center: Includes the borders of the Mediterranean Sea. Eighty-four plants are listed for this region including olives and many cultivated vegetables and forages.
Cereals and Legumes
- Durum wheat, Triticum durum expansum
- Emmer, Triticum dicoccum (one of the centers)
- Polish wheat, Triticum polonicum
- Spelt, Triticum spelta
- Mediterranean oats, Avena byzantina
- Sand oats, Avena brevis
- Canarygrass, Phalaris canariensis
- Grass pea, Lathyrus sativus
- Pea, Pisum sativum (large seeded varieties)
- Lupine, Lupinus albus, and others
Forage Plants
- Egyptian clover, Trifolium alexandrinum
- White Clover, Trifolium repens
- Crimson clover, Trifolium incarnatum
- Serradella, Ornithopus sativus
Oil and Fiber Plants
- Flax, Linum usitatissimum, and wild L. angustifolium
- Rape, Brassica napus
- Black mustard, Brassica nigra
- Olive, Olea europaea
Vegetables
- Garden beet, Beta vulgaris
- Cabbage, Brassica oleracea
- Turnip, Brassica campestris, B. napus
- Lettuce, Lactuca sativa
- Asparagus, Asparagus officinalis
- Celery, Apium graveolens
- Chicory, Cichorium intybus
- Parsnip, Pastinaca sativa
- Rhubarb, Rheum officinale
Ethereal Oil and Spice Plants
- Caraway, Carum carvi
- Anise, Pimpinella anisum
- Thyme, Thymus vulgaris
- Peppermint, Mentha piperita
- Sage, Salvia officinalis
- Hop, Humulus lupulus
VI. Abyssinian Center: Includes Abyssinia, Eritrea, and part of Somaliland. In this centre were listed 38 species. Rich in wheat and barley.
Grains and Legumes
- Abyssinian hard wheat, Triticum durum abyssinicum
- Poulard wheat, Triticum turgidum abyssinicum
- Emmer, Triticum dicoccum abyssinicum
- Polish wheat, Triticum polonicum abyssinicum
- Barley, Hordeum sativum (great diversity of forms)
- Grain sorghum, Andropogon sorghum
- Pearl millet, Pennisetum spicatum
- African millet, Eleusine coracana
- Cowpea, Vigna sinensis
- Flax, Linum usitatissimum
Miscellaneous
- Sesame, Sesamum indicum (basic center)
- Castor bean, Ricinus communis (a center)
- Garden cress, Lepidium sativum
- Coffee, Coffea arabica
- Okra, Hibiscus esculentus
- Myrrh, Commiphora abyssinicia
- Indigo, Indigofera argente
New World VII. South Mexican and Central American Central: Includes southern sections of Mexico, Guatemala, Honduras, and Costa Rica.
Grains and Legumes
- Maize, Zea mays
- Common bean, Phaseolus vulgaris
- Lima bean, Phaseolus lunatus
- Tepary bean, Phaseolus acutifolius
- Jack bean, Canavalia ensiformis
- Grain amaranth, Amaranthus paniculatus leucocarpus Melon Plants
- Malabar gourd, Cucurbita ficifolia
- Winter pumpkin, Cucurbita moshata
- Chayote, Sechium edule
Fiber Plants
- Upland cotton, Gossypium hirsutum
- Bourbon cotton, Gossypium purpurascens
- Chayote, Sechium edule
Miscellaneous
- Sweetpotato, Ipomea batatas
- Arrowroot, Maranta arundinacea
- Pepper, Capsicum annuum, C. frutescens
- Papaya, Carica papaya
- Guava, Psidium guayava
- Cashew, Anacardium occidentale
- Wild black cherry, Prunus serotina
- Cochenial, Nopalea coccinellifera
- Cherry tomato, Lycopersicum cerasiforme
- Cacao, Theobroma cacao
- Nicotiana rustica
VIII. South American Center: (62 plants listed) Three subcenters are found.
A. Peruvian, Ecuadorean, Bolivian Center: Comprised mainly of the high mountainous areas, formerly the centre of the Megalithic or Pre-Inca civilization. Endemic plants of the Puna and Sierra high-elevation districts included:
Root Tubers
- Andean potato, Solanum andigenum (96 chromosomes)
- Other endemic cultivated potato species. Fourteen or more species with chromosome numbers varying from 24 to 60.
- Edible nasturtium, Tropaeolum tuberosum. Coastal regions of Peru and non-irrigated subtropical and tropical regions of Ecuador, Peru and Bolivia included:
Grains and Legumes
- Starchy maize, Zea mays amylacea
- Lima bean, Phaseolus lunatus (secondary centre)
- Common bean, Phaseolus vulgaris (secondary centre)
Root Tubers
- Edible canna, Canna edulis
- Potato, Solanum phureja (24 chromosomes)
Vegetable Crops
- Pepino, Solanum muricatum
- Tomato, Lycopersicum esculentum
- Ground cherry, Physalis peruviana
- Pumpkin, Cucurbita maxima
- Pepper, Capsicum frutescens
Fibre Plants
- Egyptian cotton, Gossypium barbadense Fruit and Miscellaneous
- Passion flower, Passiflora ligularis
- Guava, Psidium guajava
- Heilborn, Carica candamarcensis
- Quinine tree, Cinchona calisaya
- Tobacco, Nicotiana tabacum
B. Chiloe Center (Island near the coast of southern Chile)
- Common potato, Solanum tubersum (48 chromosomes)
- Wild strawberry, Fragaria chiloensis
C. Brazilian-Paraguayan Center
- Manioc, Manihot utilissima
- Peanut, Arachis hypogaea
- Rubber tree, Hevea brasiliensis
- Pineapple, Ananas comosa
- Brazil nut, Bertholletia excelsa
- Cashew, Anacardium occidentale
- Purple granadilla, Passiflora edulis
Microcentres: Small areas within the centres of diversity exhibit tremendous genetic diversity of some crop plants. These areas are referred to as micro-centres. Microcentres are an important source for collecting valuable plant forms and for studying the evolution of cultivated species.
Distribution of species
The distribution of species refers to the geographic range in which a particular species is found. This can vary from a small, localized area to a widespread distribution across multiple continents. The distribution of species is influenced by a variety of factors, including historical events, climate, habitat availability, and biotic interactions.
In the context of agriculture, understanding the distribution of crop species is important for crop improvement and plant breeding. This knowledge helps to identify regions where crops are well-adapted and have high genetic diversity, which can be used to develop new crop varieties with desirable traits. It can also inform the development of conservation strategies to protect rare or endangered crop species.
Here are some examples of the distribution of important crop species:
- Wheat - Wheat is one of the most widely cultivated cereal crops in the world and is adapted to a wide range of environments, from temperate to tropical regions. The primary centres of wheat cultivation are the Mediterranean region, Central Asia, and North America, with additional cultivation in Europe, South Asia, and China.
- Maize - Maize, also known as corn, is a staple crop in many parts of the world and is adapted to a range of climates, from temperate to tropical regions. The primary centres of maize cultivation are Mesoamerica, where it originated, and North America, with additional cultivation in South America, Africa, and Asia.
- Rice - Rice is the primary staple crop for more than half of the world's population and is adapted to wetland environments. The primary centres of rice cultivation are Southeast Asia, where it originated, and East Asia, with additional cultivation in South Asia, Africa, and Latin America.
- Potato - Potato is an important crop for food and industrial uses and is adapted to a range of temperate climates. The primary centres of potato cultivation are the Andean region, where it originated, and Europe, with additional cultivation in North America, Asia, and Africa.
- Soybean - Soybean is an important source of protein and oil and is adapted to a range of climates, from temperate to tropical regions. The primary centres of soybean cultivation are East Asia, where it originated, and North and South America, with additional cultivation in Europe and Africa.
Understanding the distribution of these and other crop species is essential for developing new crop varieties that are well-adapted to different environments and can help to meet the growing demand for food in a changing climate.