BiologyExam code: 4BI1
Selective Breeding
Use of Biological Resources
Most of our staple food crops have been transformed by thousands of years of selective breeding.
Common goals for plant breeding
| Goal | Why it matters |
|---|---|
| Higher yield | More food per hectare of farmland |
| Disease resistance | Less crop lost to fungal, viral or bacterial disease |
| Pest resistance | Less reliance on chemical pesticides |
| Drought tolerance | Crops survive in drier climates and use less irrigation |
| Tolerance to extreme temperatures | Crops can be grown in more places |
| Better taste, colour or shelf life | More commercially valuable |
| Larger fruits or grains | More food per plant |
| Shorter growing season | Two or three crops per year instead of one |
Other plant examples
- Apples: selected for sweetness, juice content, colour and shelf life
- Bananas: the supermarket banana is a single variety (Cavendish), selected for size, sweetness, lack of seeds. It is now seriously threatened by Panama disease, partly because every plant in the world is a clone
- Maize (corn): descended from a Mexican grass called teosinte that had tiny ears with just a few grains. Modern maize cobs have hundreds of huge grains
- Roses: bred in thousands of varieties for flower size, colour and scent (rather than for food)