By Barbara Liston

ORLANDO, Fla., Nov 8 (Reuters) - The Mormon church is poised to become the largest private landowner in Florida as a result of a deal to buy nearly 400,000 acres in the state's Panhandle region.

The property is mostly timberland, and the church "intends to maintain timber and agricultural uses of the lands," according to a statement released by St. Joe Company, a Florida real estate firm.

The signed sales agreement with the church's company, AgReserves Inc., for $565 million is subject to regulatory and shareholder approvals, according to the statement. The company expects the deal to be finalized in the first quarter of 2014.

Paul Genho, chairman of AgReserves, Inc., in St. Joe's statement, described the entity as a "tax-paying affiliate of The Church of Jesus Christ of Latter-day Saints," also known as the Mormon church.

The Mormon church was already one of Florida's largest landowners. For more than 60 years, the church has owned Deseret Ranches, a 290,000 cattle and citrus operation straddling three counties in Central Florida, approximately 50 miles southeast of downtown Orlando.

Deseret operates the largest cow-calf ranch in the nation with 44,000 head of cattle, according to a ranking by the trade publication Northern Ag Network.

Deseret's website states it is owned by Farmland Reserves which is a non-profit company. Another firm, Deseret Cattle and Citrus, which is responsible for ranch operations, is a division of AgReserves.

The addition of St. Joe's 382,834 acres brings the church's Florida holdings to 672,834 acres, or almost 2 percent of the state's land mass. The total does not include smaller isolated church parcels for its Orlando and South Florida temples and other interests.

St. Joe, which once owned a million acres and was created as a paper mill enterprise by a member of the family that founded the chemical company DuPont, will shrink its holdings dramatically to 184,000 acres primarily in Northwest Florida for future real estate development, according to the company's statement.

Although virtually all of the church's holdings remain in rural and agricultural uses, the church has plans approved by Osceola County for future development of a 19,000-acre section of the Deseret Ranches located 10 miles from Orlando International Airport. The area is near the route of the All Aboard Florida privately funded train between Orlando and Miami planned for a 2015 launch.