CFR /  Title 40  /  Part 174  /  Sec. 174.526 Hygromycin B phosphotransferase (APH4) marker protein in

Residues of the Hygromycin B phosphotransferase (APH4) enzyme in all plants are exempt from the requirement of a tolerance when used as a plant-incorporated protectant inert ingredient in cotton. [72 FR 20435, Apr. 25, 2007]