Answer based on context:

After an emotional home win over the Texans, the Chargers flew to the Hubert H. Humphrey Metrodome for a Week 9 interconference duel with the Minnesota Vikings.  In the first quarter, San Diego struck first with RB LaDainian Tomlinson getting a 1-yard TD run.  The Vikings would respond with RB Adrian Peterson getting a 1-yard TD run.  In the second quarter, no scoring would come until the final play of the half, as CB Antonio Cromartie returned a missed field goal 109 yards for a touchdown, the longest play in NFL history. In the third quarter, things started to get grim for San Diego as Minnesota took the lead with Peterson getting a 64-yard TD run and QB Brooks Bollinger completing a 40-yard TD pass to WR Sidney Rice.  In the fourth quarter, the Chargers tried to come back as kicker Nate Kaeding nailed a 36-yard field goal.  Unfortunately, the Vikings sealed the win with Peterson getting a 46-yard TD run, along with RB Chester Taylor getting a 2-yard TD run. LaDainian Tomlinson, despite getting only 1 rushing touchdown, managed to surpass Jim Brown for most career rushing touchdowns with his 107th TD. During the game, Minnesota rookie running back Adrian Peterson broke the NFL single-game rushing record with 296 yards rushing on 30 carries.

How many touchdowns were scored in the first quarter?
2