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PLANT BREEDING AGR 3204 . GENETIC RESOURCES. GENETIC RESOURCES : Resources that contain all genetic variability found in a particular plant species This includes its wild relatives; m ost of them may have traits useful to breeders. GERMPLASM:
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PLANT BREEDING • AGR 3204 GENETIC RESOURCES
GENETIC RESOURCES: • Resources that contain all genetic variability found in a particular plant species • This includes its wild relatives; most of them may have traits useful to breeders. • GERMPLASM: • Overall genetic materials possessed by the plant species
Categories of Genetic Resources (Hawkes, 1983) • Crops • Current commercial cultivars. • Old commercial cultivars - no longer planted commercially. • Breeders’ seeds. • Mutants from induced or spontaneous mutations. • Land Race Usually from isolated areas or farms. Primitive crops, usually possessing high variations and grown in mixtures of genotypes, and sometimes species.
Categories of Genetic Resource (Cont.) Weedy Race • Plants that originated from same progenitor of the crop species, but possess weedy traits, such as small stem. • Capable of invading open fields rapidly, even with low soil fertility.
Categories of Genetic Resources (Cont.) • Wild species Species from the same genus that could be crossable to a certain crop species.
CENTRES OF ORIGIN AND CENTRES OF PLANT DIVERSITY Vavilov (1887-1941), a Russian botanist studied diversity and distribution of plants in the world from 1920’s to 1930’s, and found that: • There are higher levels of diversity in certain parts / regions in the world for certain kinds of plant. • Revealed eight centres of origin for main crops.
1. Chinese Center (China) • Cereal and legumes: eg: Soybeans (Glycine max) • Roots, vegetables eg: Radish(Raphanussativus) chinese cabbage (Brassicarapachinensis) • Fruits and nuts eg: Oranges (Citrus sinensis), litchi (Litchi chinensis) • Sugar, drug plants eg: Tea (Camellia sinensis), sugar cane (Saccharum sp.)
2. Indian Center • Cereal and legumes eg: Rice (Oryza sativa), chick pea (Cicerarietinum) • Vegetables and tubers eg: Egg plant (Solanummelongena) Cucumber (Cucumissativus) • Sugar, oil, fiber plants eg: sugar cane (Saccharum spp.), kenaf (Hibiscus cannabinus) • Spices eg: Black pepper(Piper nigrum)
2a. Indo-Malayan Center • Fruits eg: Pomelo (Citrus maxima), Banana (Musa spp.) Coconut (Cocosnucifera), mangosteen (Garciniamangostana), Durian (Duriozibethinus) • Oil, sugar, spice plants eg: Nutmeg (Myristicafragrans),Cloves (Syzygiumaromaticum)
3. Central Asiatic Center • Grains and legumes eg: Wheat(Triticumaestivum), Pea (Pisumsativum) • Vegetables eg: Carrot (Daucuscarota), spinach (Spinaciaoleracea) • Fruits eg: Apple (Maluspumila), grape (Vitisvinifera)
Distribution and origin of plants Central Asia
4. Near Eastern Center • Grain and legumes eg: Wheat (Triticumaestivum), Barley (Hordeumvulgare) • Fruits eg: Melon (Cucumismelo), Pomegranate (Punicagranatum) • Forage plants eg: alfalfa (Medicagosativa)
Distribution and origin of plants Near East
5. Mediterranean Center • Cereal and legumes eg: Wheat (Triticum durum), oats (Avenasativa), Broadbean (Viciafaba) • Oil and fiber plants eg: Olive (Oleaeuropaea) , black mustard (Brassicanigra) • Vegetables eg: Cabbage (Brassicaoleracea) • Ethereal oil and spices eg: peppermint (Mentha spp.), thyme (Thymus mongolicus)
6. Abyssinian/Ethiopian (African) Center • Grains and legumes eg: Wheat (Triticum durum), Barley (Hordeumvulgare) • Misc: Coffee (Coffeaarabica), okra (Abelmochusesculentus) • Oil palm (Elaeisguineensis)
Distribution and origin of plants /Ethiopian (African)
7. South Mexican and Central American Center • Grain and legumes eg: Corn (Zeamays), Common bean (Phaseolusvulgaris) • Melon plants eg: Pumpkin (Cucurbita spp.) • Misc: Chilli (Capsicum annum), cocoa (Theobroma cacao)
Distribution and origin of plants South Mexican & Central American Center
8. South American (Peruvian-Ecuadorean-Bolivian) Center • Root tubers eg: Sweet potato (Ipomoea batatas), Potato (Solanumtuberosum) • Vegetable crops eg: Tomato (Solanumlycopersicum) • Fruits and misc eg: Papaya (Carica papaya), Tobacco (Nicotianatabacum)
8a. Chilean Center Distribution and origin of plants • Potato (Solanumtuberosum)
8b. Brazilian-Paraguayan Center • Cassava (Manihotesculenta) • Groundnut (Arachishypogea) • Cocoa (Theobroma cacao) • Rubber (Heveabrasiliensis) • Pineapple (Ananascomosus) • Passion Fruit (Passifloraedulis)
GERMPLASM CONSERVATION Erosion or loss of genetic resources happened and is continuously happening at a serious rate due to: • Deforestation – Lost of wild species and weedy races. • Use of modern varieties – Lost of land races, primitive crops and weedy races. • Development –Lost of land races, primitive crops varieties, etc. Therefore, conservation is needed to conserve crop genes and genotypes, to prevent genetic vulnerability
STEPS IN GERMPLASM CONSERVATION 1. Exploration • Exploration is done to understand the crop distribution. • Plant collection is conducted to obtain samples that consist the maximum genetic diversity. Where? Native habitats of selected crop Farm where crop is planted, including small farm Market Other entities/ institutions
STEPS IN GERMPLASM CONSERVATION (cont.) 2. Collection • Random sampling To obtain variation that represents population of the crop. • Selected sampling Done for plants with specific character. The collection may not represent the actual variation. Therefore, selected sampling has to be done concurrent with random sampling.
STEPS IN GERMPLASM CONSERVATION (Cont.) 3.Maintenance / Conservation • In situ – grown in natural habitat Maintain the original forest ecosystem, grassland, Vavilov’s centre of diversity, forest parks.
Maintenance / Conservation (Cont.) b)Ex-situ • Collections Seed bank Requirement: Cold room, 10oC Relative Humidity, 2-5% • Living Plants Botanical Gardens Arboretum Field genebanks Maize seed bank arboretum
3. Storage (Conservation) b)Ex-situ (Cont.) • Pollen storage Requirement: Cold room, 10oc to - 20oc Relative Humidity, 8 -25% • In-vitro method - Tissue culture– slow growth - Cryopreservation- Liquid nitrogen (-196oc)