Presbyterian (4-9) won for the first time in the series between the two schools. It was their ninth meeting over 53 years.
Appalachian State (2-8) scored the first 10 points of the game and jumped out to a 14-2 lead. But the Blue Hose came right back, using a 15-4 run -- punctuated by 3-pointers from Downing and Reggie Dillard -- to take the lead at 20-18 en route to a two-point halftime lead at 39-37.
The Mountaineers took the lead at 49-47 at 14:25 of the second half after a 7-0 run, but Presbyterian was resilient as Truss made a pair of free throws, followed by a Downing trey, to retake the lead at 53-50 and it never trailed again.
Appalachian State was led by Tab Hamilton with 33 points.
Indiana guard James Blackmon Jr., who averaged 15.8 points in 13 games before being injured last season, has withdrawn from the NBA draft.
Isaiah Briscoe has decided to withdraw from the NBA draft and will return to Kentucky for his sophomore season. Marcus Lee intends to transfer.
The Big 12/SEC Challenge will again feature Kansas and Kentucky, this time at Rupp Arena. That's not the only exciting matchup in next season's midseason conference showdown.