Minors Should have Bank A/c for MF Investments:

Minors usually do not have a bank account. Since they cannot sign the cheques and operate the bank account, it is the gurandian (be it parents or grand parents) who make the investments from their bank account.
But now SEBI has changed the rules of the game. To invest in the name of Minor, the investments should be made from their bank account. Of course the parents would sign as guardian, on behalf of the minor.

Below mentioned news article explains the same: