Efrem Bechere1, Dick L. Auld1, Peter A. Dotray2, and Lyndell V. Gilbert3. (1) Texas Tech University, Box 42122, Lubbock, TX 79409-2122, (2) Texas Tech University, Texas Agricultural Experiment Station, Texas Cooperative Extension, Department of Plant and Soil Science, MailStop 2122, Lubbock, TX 79409-2122, (3) Texas Agricultural Experiment Station, Lubbock, TX 79403, Lubbock, TX 79403
The induction of genes conferring herbicide resistance by mutagenesis could facilitate the use of imidazolinones as an alternative weed control system in upland cotton (Gossypium hirsutum L.). In 1997 and 1998, several High Plains cotton cultivars (Atlas, Explorer, Holland 338, Tejas, SC 9023, Sphinx and Rocket) were treated with 2.45% v/v EMS (ethyl methanesulfonate). The resulting mutants were then sprayed with imazethapyr and later on with imazamox with the objective of identifying tolerant mutants to this herbicide. Imazamox rates used were, 0, 87.5, 175, 350, and 700 g ai/ha. Four stable M6-M7 lines with good level of tolerance to imazamox were identified in 2004. These lines contained four genetic backgrounds – EM4-3-1 (from Explorer), SCM3-4-3 and SCM3-7-3 (from SC 9023), and RM3-8-1 (from Rocket). During 2005 and 2006, tolerant mutants with their original parents were planted in replicated trials at Lubbock and treated with the five imazamox rates. The log-logistic model was used to explain the dose-response relationship for lint yield. Excellent level of tolerance by these mutants to imazamox was observed. Imazamox doses, however, did not have a significant impact on fiber length, fiber strength and micronaire. The non-GMO cotton developed with this method is not a transgenic technology.
