A Chinese man has pled guilty to stealing patented U.S. corn seeds for his employer, an agricultural tech firm in Beijing.

Robert Mo Hailong was arrested in 2013 on charges of taking corn seeds out of Iowan fields belonging to agritech firms DuPont Pioneer, Monsanto and LG Seeds, with the intention of shipping them to China for research.

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Mo worked for Dabeinong, a Chinese biotech firm listed on the Shenzhen Stock Exchange. His sister, Mo Yun, is married to Dabeinong's billionaire CEO, Shao Genhou. She was initially charged together with her brother and five other Chinese nationals in the case, but those charges against her were dropped in July 2015 due to lack of evidence.

She's since left the U.S. The other five have also fled to China, which doesn't have an extradition treaty with the U.S.. Now, Mo Hailong is facing his punishment alone.

The lure of inbred corn

According to government prosecutors, the intellectual property of U.S. seed companies is worth an estimated $500 million. Mo's case alone has been estimated at $30 million to $40 million in trade secrets, with a value of five to eight years of research.

These patented seeds come with years of inbreeding by trial and error, which results in a crop that produces twice the average yield as what Chinese farmers have, and are more resistant to natural effects like pests and drought.

The stems of infested plants break easily, like the plant in the foreground, which is not genetically-modified.

Mo is a U.S. permanent resident who has lived in the country for nearly two decades, and his wife and children are U.S. citizens as well.

He faced 10 years in prison, but he struck a plea deal that would limit his sentence to no more than five years. Under the deal, he will reveal the farms in the Midwest that were used in the operation.

The FBI opened an investigation three years ago after DuPont Pioneer security staff's suspicions were raised when they found the Chinese men crawling around in cornfields. The FBI's investigations involved planting GPS monitors on cars and tapping phones.

DuPont Pioneer seeds in a field in Iowa.

Additional reporting by The Associated Press.