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Breeding plants

Breeding plants

  • Unfortunately, as the human population grows many people all over the world do not have enough food.
  • The World Health Organisation has said there is a ‘global food security crisis’.
  • Global food security: the ability to produce enough food in the future to feed everyone in the world.
  • As a result new varieties of crops with higher yields are being produced to provide more food resistant to herbicides and insecticides.
  • Most new plant varieties are produced by conventional breeding programmes, for example, to produce a very high yielding wheat variety. One high-yielding wheat variety is crossed with another.
  • From these, individuals producing the most grain are selected and bred together.
  • This is repeated for at least 20 generations, eventually producing a new high-yielding variety that is named and sold. This is an example of selective breeding.
  • Conventional breeding: Producing offspring by using the natural technique of cross-breeding.

Pest management strategies

  • Huge amounts of crops are lost to pests such as insects and fungal diseases. Resistant plants can be developed (Bt toxin) but the best way of combating these diseases is to use a system called integrated pest management (IPM). This uses different pest control strategies at the same time.
  • Crops like raspberries stay in the same field for many years. However annual crops can undergo crop rotation which is a 3-4 year cycle and a different crop is planted in the same field each year. Examples of crops are potatoes, oats, beans and cabbages.
  • This helps prevent the build-up of soil pests for each crop.
  • Integrated pest management for raspberries:
    • PROBLEM: Raspberry beetles lay their eggs in the developing fruit. Their larvae eat the fruit from the inside.
      • SOLUTION: Chemicals produced by the raspberry plants are put into traps, thus luring raspberry beetles which are killed by drowning soap solution.
      • SOLUTION: Pesticides are sprayed to kill raspberry beetles but are only used when the traps show that large numbers are present.
      • SOLUTION: The environment where the raspberries are grown is made attractive to natural predators of the raspberry beetles: spiders, lacewings and hoverflies.
    • PROBLEM: Viruses, transmitted by aphids, infect and kill the plants.
      • SOLUTION: Conventional breeding has developed raspberry varieties that are resistant to the aphids, so are less likely to be infected with viruses.