IOWA CITY, Iowa (AP) — Regent Ruth Harkin has fought for months against Iowa State University's plans to limit farming research at the institute that honors her husband, U.S. Sen. Tom Harkin, arguing the issue has been central to his career, according to emails released Monday.

The Harkin Institute of Public Policy was created last year to house the Democrat's papers from his four decades in Congress and study a range of subjects, but it has been embroiled in controversy. The emails add detail to a dispute over its research mission in which Ruth Harkin has played a key role — both as a wife trying to burnish her husband's legacy and a member of the university's governing board.

"The very nature of the Institute is to capitalize on Tom's papers, his work in the House and the Senate and the strengths at ISU. Why would a Senator, who has been Chairman of the Senate Agriculture (Committee) give his agriculture papers to an Institute that wasn't going to use them? Surely we can do better than this," she wrote July 19 to ISU President Steven Leath. She warned that her husband wouldn't donate his papers if the institute doesn't study agriculture — a threat Tom Harkin, an ISU alum, made publicly last week.

In another email to Leath, Ruth Harkin said "agriculture has been the centerpiece of Tom's legislative agenda" dating to 1975, noting he played a role in two major farm bills.

The e-mails were released in response to an open records request from The Associated Press.

At the center of the controversy is a memorandum of understanding signed by ISU officials last year, before Leath became president, which banned the Harkin Institute from studying agriculture. The memo was signed months after the regents created the institute and specified that agriculture and three other areas would be its main focus.

Leath withdrew that memo but substituted his own restrictions Nov. 8. The dispute became public last week when the institute's advisory board called on Leath to rescind his policy and honor the regents' original plan to allow unrestricted agriculture research.

Leath's policy said the institute can conduct agriculture research only if it directly relates to Harkin's papers and is approved by the school's Center for Agricultural and Rural Development. Leath said the policy avoids duplication, preserves CARD's position as a preeminent agricultural research organization and allows the Harkin Institute to study other topics.

But some critics, including former Iowa Board of Regents President Michael Gartner, have accused the university of stifling academic freedom and allowing powerful agricultural interests to shape the research agenda. Leath denies that.

The emails show Board of Regents President Craig Lang and President Pro Tem Bruce Rastetter — Republicans who have strong ties to agribusiness — have sought the restrictions on the institute, which they voted against creating.

Leath told Ruth Harkin about the 2011 agriculture research ban in July, shortly after learning about it himself. Citing that policy, Leath said he instructed the university's foundation to remove language mentioning agriculture from a Harkin Institute brochure.

Ruth Harkin responded that the policy was implemented without her knowledge.

Harkin Institute interim director Dave Peterson said he was assured that the Harkins had been told of the 2011 policy before he signed it. Peterson later wrote that he believed the impetus came from the Board of Regents — under Lang and Rastetter's leadership — and was passed down through the provost and dean of agriculture, an email shows.

Ruth Harkin complained in an email to Leath that Peterson had "no authority to define the institute," since the regents had done that at its inception.

"Does ISU really wish to say that agriculture research is controlled and can only come through one funnel at Iowa State?" she wrote July 24.

Leath told her in October that he proposed unspecified revisions that were rejected by Lang. Leath then issued his Nov. 8 policy, which Ruth Harkin called an agriculture research ban "in another form." Lang and Rastetter praised the final policy.

Leath told Ruth Harkin that the policy doesn't restrict academic freedom because professors can study whatever they want.

"Academic freedom 'except for agriculture,' is not academic freedom," she replied.