Flavia Pennetta's first major title - and surprise retirement announcement - drew congratulations from around the tennis world.

Serena Williams, whose bid for the calendar grand slam ended on Friday with a stunning US Open semifinal loss to eventual runner-up Roberta Vinci, tweeted: "Congrats. I'm so happy you won. You deserved it. I am also happy for the rest of your life's journey. I will miss your smile."

Pennetta is the second Italian woman to win a major championship. The first, 2010 French Open winner Francesca Schiavone, tweeted: "Fla, welcome to the club."