In 1971, Detroy Green, Department of Agronomy, Iowa State University, found sterile plants in an F4 single-plant progeny row from a cross of Hark X Harosoy Dt2Dt2. This family segregated 66 fertile to 21 sterile plants. Microspore mother cells of the sterile plants were examined, and a low level of chromosome pairing was observed, indicating that the sterile was either an asynaptic or desynaptic mutant.