Wayne Lordan© Photo Healy Racing
Petuna was well backed during the day and her supporters got their reward in the concluding mile and five maiden in Ballinrobe.
She shortened from 6/1 to 7/2 in morning trading and was sent off the 5/2 second favourite.
Wayne Lordan settled her in second behind the leader All Is Not Lost and then the pair improved to lead over two furlongs out.
The six-year-old mare bounded away in the final furlong for a decisive victory by three lengths. Swamp Fox the 7/4 favourite, tried to hunt her down but couldn't get on terms in second. Solita (4/1) came in third.
Handler Maurice Phelan said: ""She is a fair bit of stuff and is honest as the day is long.
"She'll probably handle Galway after that but I don't know whether she'll run over hurdles or in a flat handicap."
Additional reporting by Thomas Weekes
