Unable to deactivate multiple selection for radio button in mvcjqgrid

hi all

i am using mvcJqgrid.In that grid i used radio buttons to select rows .Like this
function CustomFormatter(cellvalue, options, rowobject) {
return '<input type="radio" value="Edit" onclick="showMenuItems(' + options.rowId + ')">';
}
but when i check radio button for two rows...2 radio buttons are in checked mode.but functionality is at a time i can able to check only one radio button.i am unable to resolve this.Please Guide me

ManoRama