Brinjal and potato belong to the same genus Solanum. This is because both of them show the common characteristics found in the plants of the genus Solanum - like Phyllotaxy, venation, inflorescence etc. However, breeding is not possible between the two species of brinjal and potato. Since species are a group of organism that is capable of interbreeding thus, brinjal and potato are considered to belong to two different species.
