Vice President M. Venkaiah Naidu on Thursday appealed to all state governments to make the mother tongue a compulsory subject up to primary school.Speaking on the occasion of International Mother Language Day at his native place Nellore, he asked people to take a pledge to preserve and promote their mother tongue.There was a need to strengthen the campaign to preserve the mother tongue, he said, adding that the mass media has to play a leading role in it.Inaugurating an All India Radio FM Station which will broadcast entertainment programmes in Telugu besides important information for farmers and other sections, he asserted that radio broadcasting has made a comeback in the era of continuous bombardment of visual content by myriad channels.Stating that community radio has been playing a crucial role in taking development to every corner of the country, Naidu said that in times of natural disasters, radio often becomes the saviour by communicating critical information about relief and rescue when other mediums become ineffective.