barley malt Reinheitsgebot varietals beers
The specific grains used in a particular beer is called the "grain bill".  While just about any grain can be used, most beers use barley malt as their primary source of fermentable sugars, and some beer styles mandate it be used exclusively, such as those German styles developed under Reinheitsgebot. Some beer styles can be considered varietals, in the same sense as wine, based on their malt bill.
