Why picker does not show items?

** Editor VS 2013
** Target: iOS 6.0

I am exprimenting with a picker. The picker definition as follows

var picker = new Picker() {
    Titel = "Test",
    VerticalOptions = LayoutOptions.Fill
};
picker.Items.Add("AAA");
picker.Items.Add("DDDD");
Content = new StackLayout {
    Children = { picker }
};

when I run this code, I can see the 'Test' show up and when I click it, I do not see any of the items rather it shows just 'Done'. Is there anything am I missing here?