Poster: Emerging technologies

Abs # 918: Development of Crop Plants Resistant to Treatment with the Herbicide, Dicamba

Presenter:	Behr05713ens, Mark R, mbehrens1@unl.edu
Authors	Behr05713ens, Mark R (A)   Chakraborty, Sarbani  (A)   Mutlu, Nedim  (A)   Clemente, Tom  (A)   Weeks, Donald  (A)
Affiliations:	(A): University of Nebraska

Dicamba is a cost-effective herbicide that is widely used for the control of broad-leaf weeds in the production of corn and wheat. Because of its specificity for killing dicot plants, dicamba cannot be used in the production of dicot crops such as soybeans, canola and most vegetables. In order to make dicamba useful for agricultural production of dicot crops, development of dicamba-tolerant plants has been pursued using genetic engineering techniques. A three-component enzyme system that has been found to be involved in the degradation of dicamba has been isolated and purified from Pseudomonas maltophilia. The three components are oxygenase, reductase and ferredoxin. Physical and biochemical studies have been performed to characterize each of the three enzyme components. We have shown in transgenic tobacco, tomato and Arabidopsis plants that only the oxygenase gene is needed to convey resistance to dicamba. A molecular and genetic analysis was performed on a variety of transgenic tobacco and tomato plants that showed multiple levels of resistance. Stable Mendelian inheritance of the dicamba-resistance gene was observed. The oxygenase gene has been incorporated directly into the genome of tobacco chloroplasts by particle bombardment. Plants containing the dicamba-resistance gene in the chloroplast genome showed high levels of resistance to dicamba. Agrobacterium-mediated transient expression using a chimeric gene encoding the oxygenase with a transit peptide and a GFP moeity was used to show localization of the chimeric protein to the chloroplast. Most recently transgenic soybean plants have been shown to be resistant to dicamba applied at 5 lb/acre (compared with the usual application rate in monocot crops of 0.25 lb/acre).