Corn injury from isoxaflutole has been reported in sites across the corn belt, and variation in tolerance to isoxaflutole has been observed among corn hybrids. Greenhouse trials were conducted to study the variation and the inheritance of isoxaflutole tolerance in corn. Inbred lines from two families were treated with isoxaflutole applied preemergence, at four times the typical use rate, to study plant response. Plant height of corn inbreds treated with isoxaflutole compared with the untreated control ranged from 47 to 96% among eight lines within the B73 family and from 54 to 97% among six lines within the C103 family. One tolerant and one sensitive inbred line were selected from each family. The inbred lines were crossed in the field to produce four F₁ hybrids. The four hybrids were treated with isoxaflutole in the greenhouse, and the tolerance of each hybrid was compared with the parent inbred lines. Data indicate that sensitivity to isoxaflutole is a heritable trait that is mediated by nuclear genes. Tolerance of corn hybrids to isoxaflutole can be predicted from the response of the parent inbreds.

Nomenclature: Isoxaflutole (5-cyclopropyl-4-(2-methylsulfonyl-4-trifluoromethylbenzoyl) isoxazole); corn, Zea mays L.