Oliver Norwood went close on five minutes when he curled a strike just wide from around 20 yards out and it was the Royals who started brighter in Lancashire.
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Reading continued to push for the opener, and went close via a 30-yard free kick from Nick Blackman.
The home side had their lead shortly into the second period when Garner was bundled over inside the box by Paul McShane.
Garner picked himself up to dispatch from 12 yards for his third goal in four games for North End.
The Royals pressed to restore parity and Norwood should have made it 1-1 when he fired over from close range after Blackman had seen a shot saved.
Garner came close to doubling his tally for the afternoon when he headed just wide from Paul Gallagher's cross on 71 minutes.
Preston had goalkeeper Jordan Pickford to thank for keeping them in the lead when he denied Vyrda on 74 minutes.