Presentation on theme: "GENETIC RESOURCES: Resources that contain all genetic variability found in a particular plant species This includes its wild relatives; m ost of them."— Presentation transcript:
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: Overall genetic materials possessed by the plant species
Categories of Genetic Resources (Hawkes, 1983) Crops i. Current commercial cultivars. ii. Old commercial cultivars - no longer planted commercially. iii. Breeders’ seeds. iv. 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.
Wild species Species from the same genus that could be crossable to a certain crop species. Categories of Genetic Resources (Cont.)
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. CENTRES OF ORIGIN AND CENTRES OF PLANT DIVERSITY
Cereal and legumes: eg: Soybeans (Glycine max) Roots, vegetables eg: Radish(Raphanus sativus) chinese cabbage (Brassica rapa chinensis) Fruits and nuts eg: Oranges (Citrus sinensis), litchi (Litchi chinensis) Sugar, drug plants eg: Tea (Camellia sinensis), sugar cane (Saccharum sp.) 1. Chinese Center (China)
Distribution and origin of plants / Ethiopian (African )
7. South Mexican and Central American Center Grain and legumes eg: Corn (Zea mays), Common bean (Phaseolus vulgaris) 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 (Solanum tuberosum) Vegetable crops eg: Tomato (Solanum lycopersicum) Fruits and misc eg: Papaya (Carica papaya), Tobacco (Nicotiana tabacum)
GERMPLASM CONSERVATION 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 Erosion or loss of genetic resources happened and is continuously happening at a serious rate due to:
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
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.)
STEPS IN GERMPLASM CONSERVATION (Cont.) 3.Maintenance / Conservation a) In situ – grown in natural habitat Maintain the original forest ecosystem, grassland, Vavilov’s centre of diversity, forest parks.
3. Maintenance / Conservation (Cont.) b)Ex-situ Collections Seed bank Requirement: Cold room, 10 o C 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, 10 o c to - 20 o c Relative Humidity, 8 -25% In-vitro method - Tissue culture– slow growth - Cryopreservation- Liquid nitrogen (-196 o c)