Brinjal and potato belong to the same genus solanum because of certain common characters in them. Phyllotaxy, venation, inflorescence, etc. are some of the common characters in these plants which make them the member of the same genus. But breeding between a brinjal plant and a potato plant is not possible. Since capability to interbreed is the most defining criterion for members of a particular species; hence brinjal and
potato are kept under separate species although they belong to the same genus.