(Reuters) - Two-time NCAA champion Steve Johnson has earned a wild card berth into the main draw of the 2012 U.S. Open, the United States Tennis Association (USTA) said on Monday.

The 22-year-old Johnson earned enough points to secure the wild card by winning the USTA Pro Circuit Challenger title in Aptos, California, over the weekend.

Johnson went undefeated in singles in 2012 to claim his second straight National Collegiate Athletic Association (NCAA) singles crown while leading Southern California to its fourth team title in his four years at the school.

Stanford University's 2012 NCAA doubles champion Mallory Burdette won the U.S. Open women's wild card last week.

The August 27-September 9 U.S. Open is the final gram slam tournament of the year.

(Reporting by Steve Ginsburg in Washington; Editing by Frank Pingue)