Apple Passbook mobile commerce app has more than tripled the number of Major League Baseball stadiums available. Now there are 13 American baseball options compared to last season’s four. The tickets are through the iPhone MLB At Bat app.

Packaged with last fall’s iOS update, Apple Passbook streamlines several retail apps into one user interface. In MLB’s instance, it makes digital game day tickets available on the iPhone lock screen. As with American Airlines, United and other ticket-based Passbook items, the MLB ticket appears a few hours before the purchased event.

The 2013 additions are the Baltimore Orioles, Chicago Cubs, Detroit Tigers, Kansas City Royals, Milwaukee Brewers, New York Mets, Oakland A’s, Pittsburgh Pirates and San Francisco Giants.

MLB was one of the few brands to launch on Passbook. It obviously getting support from the baseball organization, as well as other sports-affiliated brands like eBay’s StubHub.

The show of support assuages initial concerns that Passbook would actually take away customers from native apps. As we wrote in September, Apple’s design turns Passbook into a one-stop shop for individual retail apps, but lacks the deeper interactivity offered by the apps. Despite the limitations, Starbucks, Target and other early adopters saw a big uptick in their app downloads and, presumably, their number of users.