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CHAPTER 5. GENETIC RESOURCES IN AGRICULTURE. Origin and Distribution Of Crop Plants. A centre of origin means a geographical area where a plant species, either domesticated or wild , first developed . Mesoamerica . Southern Mexico, and North Central America. NORTH MEXICO

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    Origin and Distribution

    Of Crop Plants

    • A centre of origin means a geographical area where a plant species, either domesticated or wild, first developed


    • Southern Mexico, and North Central America


    Maize, Beans, Sweet Potato, Tomatoes, Cotton, Papaya, Guava, Peppers, Sunflowers, Strawberry, Grapes, Avocado


    Maize, Beans, Sweet Potato, Tomatoes, Cotton, Papaya, Guava, Peppers, Sunflowers, Strawberry, Grapes, Avocado


    Andes and South America












    Southeast Asia

    Asian rice, peas and beans, yam, breadfruit, mango, nutmeg, brinjal, cucumber, banana, plantain, coconut, orange, lime, grapefruit.



    Asian rice, soybean, green gram, orange, apricot, peach, tea, cabbage, ginger, ginseng, rape seed, chestnut, turnip, yam.



    Sorghum, Cowpea, Coffee, Melon, Watermelon,


    Oil palm, Okra, Kenaf, Brinjal.


    Southwest Asia

    Wheat, Barley, Rye, Oat, Pea, Lentil, Carrot, Radish, Safflower, Olive, Rape Seed, Walnut, Date Palm, Almond, Grape, Apple, Pear, Plum, Onion, Lettuce, Parsley.


    Dangers of Monocultures:

    Intensified agriculture meant monocultures, vast spreads of a single crop.

    This is economically efficient, but increases risk of catastrophic failure (“all eggs in one basket”).


    Crop diversity

    Monocultures also have reduced crop diversity.

    90% of all human food now comes from only 15 crop species and 8 livestock species.

    preserving crop diversity
    Preserving crop diversity
    • Native cultivars of crops are important to preserve, in case their genes are needed to overcome future pests or pathogens.
    • Diversity of cultivars has been rapidly disappearing from all crops throughout the world.
    seed banks preserve seeds crop varieties
    Seed banks preserve seeds, crop varieties
      • Seed banks are living museums of crop diversity, saving collections of seeds and growing them into plants every few years to renew the collection.
    • Careful hand pollination helps ensure plants of one type do not interbreed with plants of another.

    Figure 9.14



    • Germplasm

    - used to describe the genetic


    - precisely the DNA of an organism

    and collections of the material

    - any material of plant, animal, microbial or other origin containing functional units of heredity

    • Biodiversity, or biological diversity = the sum of an area’s organisms, considering the diversity of species, their genes, their populations, and their communities


    • Biological Diversity

    There are 3 aspects of biodiversity :

    1. Genetic diversity (within species)

    2. Species diversity (between species)

    3. Ecosystem diversity (habitat)

    • Biodiversity exists at several levels:

    Species diversity

    Genetic diversity

    Ecosystem diversity

    Figure 15.2

    genetic diversity
    Genetic diversity
    • The differences in DNA

    composition among individuals within a given species

    • Adaptation to particular

    environmental conditions may weed out weak genetic variants

    • Populations benefit from some genetic diversity, so as to avoid inbreeding or disease epidemics.

    Figure 15.2

    species diversity
    Species diversity
    • The number or variety of species in a particular region
    • Species richness = number of species
    • Evenness, or relative abundance = extent to which numbers of different species are equal or skewed
    • Species = a particular type of organism; a population or group of populations whose members share certain characteristics and can freely breed with one another and produce fertile offspring

    Figure 15.2

    ecosystem diversity
    Ecosystem diversity
    • Includes diversity above the species level
    • Biologists have viewed diversity above the species level in various ways. Some alternative ways to categorize it include:
            • Community diversity
            • Habitat diversity
            • Landscape diversity

    Figure 15.2

    measuring biodiversity
    Measuring biodiversity
    • Still ignorant of the number of species on earth
    • About 1.75 million species have been documented.
    • But many more exist: 3 to 100 million.
    measuring biodiversity1
    Measuring biodiversity

    Why still ignorant of the number of species on Earth?

    • Some areas remain little explored (hydrothermal vents, rainforest canopies, tropical soils).
    • Many species are tiny and inconspicuous (microbes, roundworms, protists, fungi…).
    • Some species are very similar in appearance (many taxa, even trees, birds, whales).
    distribution of biodiversity
    Distribution of biodiversity
    • Species are not evenly spread among different groups.
        • Insects comprise more than half of all species in world.
        • Beetles comprise fully 40% of all insects.
        • Mammals are outnumbered by spiders and their relatives 16 to 1.
    biodiversity loss and species extinction
    Biodiversity loss and species extinction
    • Extinction = last member of a species dies and the species vanishes forever from Earth
    • Extirpation = disappearance of a particular population, but not the entire species globally
    • These are natural processes.
    • On average one species goes extinct naturally every 500–1,000 years—this is the background rate of extinction.
    • 99% of all species that ever lived are now extinct.
    mass extinctions
    Mass extinctions
    • Earth has experienced five mass extinction events in which over half its species were wiped out suddenly.

    Figure 15.8

    today s mass extinction
    Today’s mass extinction
    • Currently Earth is undergoing its sixth mass extinction—because of us.
    • Humans have increased the extinction rate by a factor of 1,000.
    • 1,100 species are extinct in the past 400 years.
    • The Red List, IUCN(International Union for Conservation of Nature) lists fauna and flora species facing various risk levels of extinction.
    • (e.g Tiger, turtle, tapir, bullfrog)
    today s mass extinction1
    Today’s mass extinction
    • Species of large mammals and birds plummeted with the arrival of humans, independently, on each of three continents—suggesting that human hunting was the cause.

    Figure 15.9

    causes of species extinction
    Causes of species extinction
    • Primary causes spell “HIPPO”:
      • Habitat alteration
      • Invasive species
      • Pollution
      • Population growth
      • Overexploitation
    h ippo habitat alteration
    “HIPPO”: Habitat alteration
    • The greatest cause of extinction today
    • Accounts for 85% of population declines of birds and mammals
    • Habitat change hurts most organisms because they are adapted to an existing habitat.
    • Alteration due to:

    Forest clearing Urban development Agriculture

    Global climate change etc….

    h i ppo invasive species
    “HIPPO”: Invasive species
    • Accidental or intentional introduction of exotic species to new areas
    • Most do not establish or expand, but some do—likely because they are “released” from limitations imposed by their native predators, parasites, and competitors.
    • In today’s globalizing world,
        • invasive species have become perhaps the second- worst threat to native biota.
    hippo invasive species

    •Mosquito fish

    •Zebra mussel


    •Asian long-horned beetle

    •Rosy wolfsnail

    •Cane toad


    •Gypsy moth

    •European starling

    •Indian mongoose

    •Caulerpa algae


    •Brown tree snake

    Citrus huanglongbin, (greening)—diaphorinacitri

    “HIPPO”: Invasive species

    Figure 15.10

    hi p po pollution
    “HIPPO”: Pollution
    • Air and water pollution; agricultural runoff, industrial chemicals, etc.
    • Pollution does serious and widespread harm, but is not as threatening as the other elements of HIPPO.
    hip p o population growth
    “HIPPO”: Population growth
    • Human population growth exacerbates every other environmental problem.
    • Magnifies effects of the other elements of HIPPO:
        • More people means more habitat change, more invasive species, more pollution, more overexploitation.
    • Along with increased resource consumption, it is the ultimate reason behind proximate threats to biodiversity.
    hipp o overexploitation
    “HIPPO”: Overexploitation

    Two meanings:

    • Overharvesting of species from the wild

    (too much hunting, fishing…)

    • Overconsumption of resources

    (too much timber cutting, fossil fuel use…)

    • Usually overexploitation is not the sole cause of extinction, but it often contributes in tandem with other causes.
    causes of species extinction1
    Causes of species extinction
    • In most cases, extinctions occur because of a combination of factors.
    • e.g., current global amphibian declines are thought due to a complex combination of:
        • • Chemical contamination
        • • Disease transmission
        • • Habitat loss
        • • Ozone depletion and UV penetrance
        • • Climate change
        • • Synergistic interaction of these factors
    benefits of biodiversity
    Benefits of biodiversity
    • Preserving biodiversity preserves ecosystem services, and directly provides things of pragmatic value to us.
      • • Food, fuel, and fiber
      • • Shelter and building materials
      • • Air and water purification
      • • Waste decomposition
      • • Climate stabilization and moderation
      • • Nutrient cycling
      • • Soil fertility
      • • Pollination
      • • Pest control
      • • Genetic resources
    benefits of biodiversity food security
    Benefits of biodiversity: Food security
    • Many species not now commonly used for food could be.
    • Genetic diversity within crop species and their relatives enhances our agriculture and provides insurance against losses of prevalent strains of staple crops.

    Figure 15.11

    benefits of biodiversity medicine
    Benefits of biodiversity: Medicine
    • Many species can provide novel medicines; we don’t want to drive these extinct without ever discovering their uses.
    • Ten of our top 25 drugs come directly from wild plants; the rest we developed because of studying the chemistry of wildspecies.

    Figure 15.12

    benefits of biodiversity economic benefits
    Benefits of biodiversity: Economic benefits
    • For all nations, ecotourism can be a major contributor to the economy—especially for developing nations rich in biodiversity.
    • Affluent tourists pay good money to see wildlife, novel natural communities, and protected ecosystems.
    benefits of biodiversity biophilia
    Benefits of biodiversity: “Biophilia”
    • Biophilia = human love for and attachment to other living things;
    • “the connections that human beings subconsciously seek out with the rest of life”
    • Affinity for parks and wildlife
    • Keeping of pets
    • Valuing real estate with landscape views
    • Interest in escaping cities to go hiking, birding, fishing, hunting, backpacking…

    Agricultural resources are limited by ...

    • deforestation
    • overgrazing
    • land conversion

    Source: FAO


    With increasing demand for food and limiting resources...

    we need better and more efficient ways to produce food

    one option is through




    - life


    - any technique or procedure to develop new products



    - any technique that uses whole or part of a living thing to make new products, improve or develop plants, animals and other organisms for specific use


    GE of animals

    GE of plants

    GE to improve microorganisms

    GE to develop animal vaccines

    Recombinant DNA for disease diagnostics

    GE of biocontrol agents against plant pest & diseases

    Monoclonal anti body production

    Plant protoplast fusion

    Plant tissue culture

    Embryo transfer

    Fermentation, Biofertilizers

    Insulin for diabetes

    Interferon for treating cancer

    Hepatitis B vaccine

    Food biotechnology

    Improved food quality and food processing

    Better tasting

    More nutritious

    Cleaner food

    Animal biotechnology
    • Better breeds of livestock and poultry
      • leaner meat
      • more milk


    Crops biotechnology

    Tissue cultured planting materials

    High yielding crops

    Varieties resistant to pests and diseases

    Diagnostic kits

    Improved postharvest qualities

    Genetic engineering

    Technique that transfers gene(s) of interest to develop and improve plants, animals and other organisms


    - basic physical and functional units of heredity which carries information for the expression of a particular trait


    Crop Plant

    Wild Relative

    Wild Relative

    Crop Plant

    Genetic Engineering

    Conventional Breeding


    Genetic Engineering

    Conventional Breeding

    • limited to exchanges between the same or very closely related species
    • little or no guarantee of obtaining any particular gene combination from the millions of crosses generated
    • undesirable genes can be transferred along with desirable genes
    • take a long time to achieve desired results
    • allows the direct transfer of one or just a few genes, between either closely or distantly related organisms
    • crop improvement can be achieved in a shorter time compared to conventional breeding

    Genetically Modified Organisms (GMOs)

    = Transgenics

    Products developed through genetic engineering


    2001 & 2002

    (millions of hectares)

    Global area by country

    prevalence of gm foods
    Prevalence of GM foods
    • Although many early GM crops ran into bad publicity or other problems, biotechnology is already transforming the U.S. food supply.
    • Two-thirds of U.S. soybeans, corn, and cotton are now genetically modified strains.
    prevalence of gm foods1
    Prevalence of GM foods
    • 6 million farmers in 16 nations plant GM crops.
    • But most are grown by 4 nations.
    • The U.S. grows 66% of the world’s GM crops.
    • number of plantings have

    grown >10%/year

    Figure 9.13



    Global area by year

    Increase of 12%, 6.1 million hectares or 15 million acres between 2001 and 2002.

    Source: Clive James, 2002


    Global area by crop

    2001 and 2002:

    (million hectares)




    Industrial Countries



    Developing Countries






    Source: Clive James, 2002

    Global area (Industrial vs. Developing)

    2001 and 2002:

    (million hectares)

    scientific concerns about gm organisms
    Scientific concerns about GM organisms
    • Are there health risks for people?
    • Can transgenes escape into wild plants, pollute ecosystems, harm organisms?
    • Can pests evolve resistance to GM crops just as they can to pesticides?
    • Can transgenes jump from crops to weeds and make them into “superweeds”?
    • Can transgenes get into traditional native crop races and ruin their integrity?
    scientific concerns about gm organisms1
    Scientific concerns about GM organisms
    • These questions are not fully answered yet.
    • In the meantime…

    Should we not worry, because so many U.S. crops are already GM and little drastic harm is apparent?

    Or should we adopt the precautionary principle, the idea that one should take no new action until its ramifications are understood?

    socioeconomic and political concerns about gm products
    Socioeconomic and political concerns about GM products
    • Should scientists and corporations be “tinkering with” our food supply?
    • Are biotech corporations testing their products adequately, and is outside oversight adequate?
    • Should large multinational corporations exercise power over global agriculture and small farmers?
    europe vs america
    Europe vs. America
    • Europe: has followed precautionary principle in approach to GM foods. Governments have listened to popular opposition among their citizens.
    • U.S.: GM foods were introduced and accepted with relatively little public debate.
    • Relations over agricultural trade have been uneasy, and it remains to be seen whether Europe will accept more GM foods from the U.S.

    1.Divide into groups of 5

    2. Each person should get at least 10 respondents

    3. Carry out the survey until the 12th week

    4. Coding and data preparation in excel

    5. Analysis in SPSS

    6. Presentation in week 13 and 14

    7. Full Report by 15th week