When traits are controlled by three or more genes, they are called polygenic traits and their inheritance is called as polygenic inheritance. Polygenic inheritance is influenced by the environment as well and not just the polygenes.

Kernel colour of wheat is regulated AA and BB that is two pairs of genes. Genes A and B express the red colour of kernel. They are dominant over their recessive alleles. When a red kernel wheat variety is crossed with white kernel wheat, the ratio obtained in ${\mathrm{F}}_2$ is $1\mathrm{ }:\mathrm{ }4\mathrm{ }:\mathrm{ }6\mathrm{ }:\mathrm{ }4\mathrm{ }:\mathrm{ }1$ due to the polygenic inheritance.