UPDATE 1-First Horizon posts wider quarterly loss

* Q2 loss $0.58 vs loss $0.10 a year ago

* Q2 provision for bad loans up 18 pct

NEW YORK, July 17 (Reuters) - First Horizon National Corp (FHN.N) posted its fifth straight quarterly loss on Friday as the largest bank in Tennessee continues to struggle with its mortgage and commercial loans.

The second-quarter loss available to common shareholders was $123.2 million, or 58 cents a share, compared with a loss of $19.1 million, or 10 cents a share, in the year-ago period.

The Memphis-based company has been battered by losses on residential real estate and commercial loans as house prices have slumped amid the recession.

Net charge-offs were $239.4 million for the quarter, while provisions for bad loans rose 18 percent to $260.0 million.

The bank received an $866 million cash infusion under the U.S. government's Troubled Asset Relief Program in October.

Shares of First Horizon closed at $12.68 on Thursday on the New York Stock Exchange. (Reporting by Sweta Singh; Editing by John Wallace)