Selective Breeding in Plants (Edexcel IGCSE Biology: Double Science)

Selective breeding definition

• Selective breeding or artificial selection means to select individuals with desirable characteristics and breed them together
• The process doesn’t stop there though because it’s likely that not all of the offspring will show the characteristics you want so offspring that do show the desired characteristics are selected and bred together
• This process has to be repeated for many successive generations before you can definitely say you have a ‘new breed’ that will reliably show those selected characteristics in all offspring

Selective breeding in plants

• Plants are selectively bred by humans for development of many characteristics, including:
  • Disease resistance in food crops
  • Increased crop yield
  • Hardiness to weather conditions (e.g. drought tolerance)
  • Better tasting fruits
  • Large or unusual flowers
• An example of a plant that has been selectively bred in multiple ways is wild brassica, which has given rise to cauliflower, cabbage, broccoli, Brussels sprouts, kale and kohlrabi:

An example of selective breeding in plants

Problems with selective breeding

• Selective breeding can lead to ‘inbreeding’
• This occurs when only the ‘best’ animals or plants (which are closely related to each other) are bred together
• This results in a reduction in the gene pool – this is a reduction in the number of alleles (different versions of genes) in a population
• As inbreeding limits the size of the gene pool, there is an increased chance of:
  • Organisms inheriting harmful genetic defects
  • Organisms being vulnerable to new diseases (there is less chance of resistant alleles being present in the reduced gene pool)