ARS | Publication request: Explanation of the Differences in Sweet Corn Hybrid Sensitivity to HPPD-inhibitors

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: September 30, 2009
Publication Date: February 7, 2010
Citation: Williams, M., Pataky, J.K. 2010. Explanation of the Differences in Sweet Corn Hybrid Sensitivity to HPPD-inhibitors. Weed Science Society of America Meeting Abstracts. Available: http://www.wssa.net/Meetings/WSSAAbstracts/abstractsearch.php.

Technical Abstract: Mutation of a cytochrome P450 (CYP) allele on the short arm of chromosome 5 affects sensitivity in sweet corn to mesotrione and tembotrione applied postemergence. Hybrids that are homozygous for the functional allele (CYPCYP) are tolerant of both herbicides and rarely injured at recommended use rates, while hybrids that are homozygous for mutant alleles (cypcyp) are frequently injured. Responses to mesotrione and tembotrione differ between hybrids that are heterozygous for a functional and mutant allele (CYPcyp). Reports of injury to sweet corn from topramezone are scarce. The objectives of this work were 1) to conduct a side-by-side comparison of sweet corn hybrid response to mesotrione, tembotrione, and topramezone under field conditions, and 2) to compare dose-response relationships among CYPCYP, CYPcyp, and cypcyp hybrids. Among HPPD-inhibitors used postemergence in sweet corn, topramezone is safe on the nearly 600 hybrids tested, in part because of the low use rate. When environmental conditions favor crop injury (e.g. including urea ammonium nitrate in spray solution; moist conditions preceding application), mesotrione injures the largest number of hybrids and these hybrids are almost exclusively cypcyp or CYPcyp. Isoxadifen-ethyl in the tembotrione product greatly reduces occurrence of injury in CYPcyp hybrids, but not in cypcyp hybrids. Despite a common genetic basis among several P450-metabolized herbicides, sweet corn hybrids do not have identical responses to mesotrione, tembotrione, and topramezone, in part because of alleles affecting sensitivity as well as inherent differences in product formulations and use rates.