Two sterile plants were found in a commercial field of soybeans in Ames in 1977. The plants were noticed because of their retention of chlorophyll when fertile plants had matured and turned brown. One of the plants, 'Sterile A', had set two one-seeded pods, and the other, 'Sterile B', had set 7 seeds.
Stelly, David M.; Muir, Patricia S.; and Palmer, Reid G.
"Research notes: Spontaneously occurring sterile plants,"
Soybean Genetics Newsletter: Vol. 6
, Article 22.
Available at: http://lib.dr.iastate.edu/soybeangenetics/vol6/iss1/22