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Title: Genetic basis and implications of cross-sensitivity in Zea mays L. (sweet corn) to multiple herbicides metabolized by cytochrome P-450 enzymes

item Williams, Martin
item Sims, Gerald

Submitted to: International Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2008
Publication Date: 6/19/2008
Citation: Williams, M., Pataky, J.K., Riechers, D.E. 2008. Genetic basis and implications of cross-sensitivity in Zea mays L. (sweet corn) to multiple herbicides metabolized by cytochrome P-450 enzymes [abstract]. In: Abstracts of 5th International Weed Science Congress June 23-27, 2008, Vancouver, British Columbia, Canada. 2008 CDROM.

Interpretive Summary:

Technical Abstract: Certain Zea mays L. (sweet corn) hybrids and inbreds can be injured or killed following postemergence applications of several herbicides metabolized by cytochrome P-450 enzymes. Identification of sensitive hybrids in annual screening trials, the primary means of guiding weed management decisions, is limited because of high turnover of commercial hybrids. In recent years, our research team has pursued a mechanistic understanding of the genetic basis for herbicide sensitivity in Zea mays. Classical inheritance studies and segregating mapping populations determined that sensitivity to eight herbicide treatments (foramsulfuron, nicosulfuron, primisulfuron, rimsulfuron, mesotrione, tembotrione, carfentrazone, and dicamba + diflufenzopyr) representing four modes of action (ALS-inhibiting, HPPD-inhibiting, PPO-inhibiting, and growth regulating) was simply inherited in inbred Cr1, and that a single gene(or very closely-linked genes) conditioned cross-sensitivity to all herbicides tested. The gene(s) was subsequently mapped to the same region of chromosome 5S as a cytochrome P-450 gene that previously was designated as nsf1 or ben1, which resulted from its ability to condition sensitivity to nicosulfuron and bentazon in Zea mays (field corn). Additional research found 45 hybrids and 29 inbreds from 12 different seed and food processing companies were either homozygous or heterozygous for the gene(s) of interest in Cr1. Evironment has an influence on level of crop injury, and we found that genotypic classes of Zea mays hybrids (i.e., homozygous tolerant, heterozygous, and homozygous sensitive) explained differences in herbicide responses of hybrids in 12 trials from Idaho to Delaware. When injury was observed, homozygous sensitive hybrids were injured severely. Heterozygous hybrids had a response that was intermediate to homozygous sensitive or homozygous tolerant hybrids. Injury to heterozygous hybrids was 1.5 to 2.3 times greater than homozygous tolerant hybrids. These results provide seed companies, herbicide manufacturers, and regulatory agencies information needed to make more informed decisions about risks of crop injury.