Can we achieve the cascading pageblock section style in Visual-force page? let user click on (+) corresponding subsection should expand in fashion in image attached.
You can nest apex:pageBlockSection elements and the section open/close behaves as you would expect.
For example, just create this page and try it:
But your screen shot shows something that in no way matches the styling that Visualforce provides out of the box, so if that is important you might be better off embedding some other technology in the Visualforce page such as one of these jQuery Treeview Plugin & Tutorials with Example.