CHICAGO (Reuters) -A biological sample that a Chinese researcher was accused of smuggling into the United States and that prosecutors cast as a "dangerous biological pathogen" is a common type of fungus already widespread in U.S. crop fields that likely poses little risk to food safety, experts said. On Tuesday, U.S. federal prosecutors accused two Chinese researchers of smuggling samples of the fungus Fusarium graminearum into the U.S., describing it as a potential agricultural terrorism weapon. Yunqing Jian, 33, a researcher at the University of Michigan's Department of Molecular, Cellular and Developmental Biology has been charged in connection with allegations that she helped her boyfriend, Zunyong Liu, 34, smuggle the pathogen into the U.S.