The first portion of the wedding ceremony is known as the Erusin or Qiddushin. In former years it used to be done sometime earlier than the rest of the ceremony, which is the Nissuin or the Huppah. Nowadays, of course, both portions of the wedding ceremony are done together.
The custom is that the Berakha of the Erusin is proceeded by a "Boreh Peri HaGefen over the wine and the reason for that being that this is a blessing (Berakha) of Simha (happiness) and that is the reason why we have the wine. The blessing of the wine is recited first followed by the Berakha of the Erusin.
In a case where there is no wine available, however, the blessing of the Erusin is recited by itself without the "Boreh Peree HaGefen".
(See Ben Ish Hai, Shana Aleph, Parashath Shoftim. Oth Geemal)
