Explain how selective breeding could be used to produce a new variety of wheat plant that has a higher resistance to fungal disease.

Pearson Edexcel International GCSE Biology (4BI1) — 5.2 Selective breeding · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Wheat crops worldwide are frequently damaged by fungal diseases, reducing yields. Farmers and plant breeders want to develop wheat varieties that can resist these diseases without relying on chemical pesticides.

Model answer (4 marks)

Identify wheat plants that show the greatest resistance to fungal disease from the existing population.
Cross‑breed or interbreed the selected resistant plants with each other.
Select the offspring that show the greatest resistance to fungal disease and breed them together again.
Repeat this process over many generations until offspring consistently show high resistance to fungal disease.

Examiner tips

Use the exact wording from the mark scheme – ‘identify’, ‘cross‑breed’, ‘select’, ‘repeat’. Show the sequence of steps in order. Mention that the process is repeated over many generations to achieve consistency.

Common mistakes

Writing the steps in the wrong order. Using vague terms like ‘improve’ instead of ‘select’ or ‘breed’.

Mark scheme (4 marks)

Identify and select wheat plants that show the greatest resistance to fungal disease (from the existing population)
Cross-breed / interbreed the selected resistant plants with each other
Select the offspring that show the greatest resistance to fungal disease and breed them together again
Repeat this process over many generations until offspring consistently show high resistance to fungal disease

Key terms in this question

selective breeding