The owners of all property sought to be condemned for the proposed improvement shall be made parties defendant. It shall not be necessary to make any person a defendant unless such person has some title thereto of record in the office of the county clerk and recorder of the county or city and county in which said property is situated. If the proceeding seeks to affect land owned by an infant or a mentally incompetent person, the legal guardian or conservator of such person shall be made a party defendant. If such person has no legal guardian, the district court shall have the power to appoint a guardian ad litem to represent such person.