In 1921 he became Donald F. Jones's assistant in Connecticut and simultaneously furthered his studies at Harvard University, attaining his doctorate in 1925 under the direction of E. M. East.
In 1927 Mangelsdorf became a researcher at the Texas Agricultural Experiment Station, where he became interested in the genetic origins of maize.
[3] In 1941, Mangelsdorf became an agricultural consultant for the Rockefeller Foundation and was involved in the development of Office of Special Services that became the International Maize and Wheat Improvement Center.
[5] According to the horticultural authority Noel Kingsbury, this theory enjoyed broad support on the strength of Mangelsdorf's "undisputed... reign as the international emperor of corn."
However, advances in molecular genetics discredited the tripartite model in favor of the rival position of George Beadle, which identified corn as a domesticated offspring of teosinte.