|Auld, Dick - TEXAS TECH UNIVERSITY|
|Dotrax, Peter - TEXAS TECH UNIVERSITY|
|Gilbert, Lyndell - TEXAS TECH UNIVERSITY|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2009
Publication Date: August 25, 2009
Citation: Bechere, E., Auld, D.L., Dotrax, P.A., Gilbert, L.V., Kebede, H.A. 2009. Imazamox Tolerance in Mutation Derived Lines of Upland Cotton. Crop Science. Interpretive Summary: Weed control in most cotton fields is by almost exclusive use of the broad-spectrum herbicide glyphosate. With such dependence on one herbicide has come concern for development and spread of weeds that are tolerant (not killed) to this herbicide. There are now eleven weeds that have some plants that are tolerant to normal application levels of glyphosate. Cotton lines with tolerance to another herbicide with a different mode of action will increase weed management tools available to cotton growers. Eight commercial cotton varieties were treated with a chemical that causes changes to plant DNA, and selections from these mutant populations produced lines that exhibited elevated levels of tolerance to imazamox, another herbicide that kills a broad spectrum of weeds. The imazamox-tolerant mutants developed into normal plants when sprayed with the herbicide, while the non-mutated cultivars turned yellow, were stunted and their lint yield were substantially reduced. These cotton lines with tolerance to imazamox can be used to develop cultivars that can be used in fields where the use of glyphosate is no longer an effective option.
Technical Abstract: Induction of genes conferring herbicide resistance by mutagenesis could facilitate use of imidazolinone herbicides in upland cotton (Gossypium hirsutum L.). In 1997 and 1998, seeds of eight High Plains cotton cultivars were treated with 2.45% v/v EMS (ethyl methane sulfonate). The resulting M3 and M4 (mutant generations 3 and 4) were sprayed with imazethapyr, and the M5 and M6 generations were sprayed with imazamox. Four stable M6-M7 lines with tolerance to imazamox were identified in 2004. During 2005 and 2006, tolerant mutants and their non-mutated parents were treated at the four leaf stage with topical applications of imazamox applied at five rates (0, 88, 175, 350, and 700 g a.i. ha-1). Elevated levels of tolerance to imazamox were observed in all mutants. Imazamox did not impact fiber length. Preliminary investigation indicated that tolerance to imazamox was controlled by a partially dominant single gene. Allelism tests revealed that the tolerance genes in the four mutants are either alleles in the same locus or are very tightly linked.