Denny Johnstone scored a brace as Morton beat Queen of the South 2-0 to move up to fourth in the Ladbrokes Scottish Championship table.The hosts had a number of chances to take the lead in the first-half but could not find a way past Queen of the South goalkeeper Robbie Thomson.The Ton finally made the breakthrough six minutes after the break when Johnstone found the top corner of Thomson's net from 20 yards.And Johnstone doubled his side's advantage 11 minutes later when he got on the end of Ross Forbes' corner to nod in from close range.