Registration of four upland cotton (gossypium hirsutum L.) genetic stock mutants with tolerance to imazamox

Few mutants conferring herbicide tolerance in cotton (Gossypium hirsutum L.) have been developed. Imazamox {2-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-5-methoxymethylnicotinic acid} is a broad spectrum imidazolinone herbicide that could give growers a new tool to control many troublesome annual broadleaf and grass weeds. Our objective was to identify imazamox tolerance in chemical mutation derived cotton lines. Four imazamox tolerant mutant cotton (G. hirsutum) genetic stocks, SCM₃-4-3 (Reg. No. GS-3, PI 657941), SCM₃-7-3 (Reg. No. GS-4, PI 657942), RM₃-8-1 (Reg. No. GS-5, PI 657943), and EM₄-3-1 (Reg. No. GS-6, PI 657944) were developed and jointly released by Texas Tech University, Department of Plant and Soil Science, and USDA-ARS Crop Genetics and Production Research Unit,Stoneville, MS, in July, 2009. These genetic stocks were obtained through ethyl methanesulfonate (EMS) mutagenesis of seeds of three High Plains cotton cultivars (SC 9023, Rocket, and Explorer) and selection with imazamox herbicide. Application of five rates of imazamox (0, 88, 175, 350, and 700 g a.i. ha^-1) has shown that these mutants have elevated levels of tolerance to imazamox. These genetic stocks are available for use by the cotton industry and public researchers to create hybrids, parental lines, or germplasm lines with resistance to the imazamox herbicide. The identification of these mutants is expected to increase weed management options available to conventional growers who have become heavily dependent on glyphosate [N-(phosphonomethyl) glycine] based crop production systems.