Nevertheless it was Morton who made the more promising start, Ryan Harding heading wide from a John Adam corner.
The home side continued to press but Gretna opened the scoring at the other end when, from Andy Aitken's free-kick, Chris Innes hoisted a high ball into the box and, when Harding and Derek Lilley failed to clear, Derek Townsley squared for Kenny Deuchar to tap in from close range.
Jim McAlister raised home hopes with an angular volley which flew over after an exciting left-wing run, but an equaliser nearly came when Alan Main made a dreadful hash of a save from Chris Millar, flapping weakly at the ball and almost turning it into the net.
David Bingham headed a Gavin Skelton corner just wide as Gretna sought to extend their lead, but Morton had the cruellest of luck in first-half stoppage time when a thunderous drive from all of 35 yards by Alex Walker crashed off the underside of the bar.
'Ton surged forward from the restart, but efforts from Millar, Chris Templeman and Lilley sailed harmlessly into the terracing.
Referee Sproul enraged the home support with several bizarre decisions but, in reality, Gretna's defenders, in particular, Townsley, who made a stunning block to prevent Lilley scoring, were in outstanding form.
Gretna clinched the three points 10 minutes from time when Ryan McGuffie met Ryan Baldacchino's corner at the near post to head in number two.