Herbicide resistance crops

Legere, A. (2005). Risks and consequences of gene flow from herbicide-resistant crops canola (Brassica napus L) as a case study , Pest Manag Sci., 61, 292-300. 

Herbicide market, 13 285-286 Herbicide-resistant crops (HRCs),... 

Padgette, S. R., Re, D. B., Barry, G. F. el al. (1994). New weed control opportunities development of soybeans with a Roundup Ready gene. In Herbicide-resistant Crops Agricultural, Economics, Environmental, Regulatory, and Technologycal Aspects, ed. S. O. Duke. Boca Raton, FL CRC Press. 

Forcella, F. (1987). Herbicide-resistant crops Yield penalties and weed thresholds for oilseed rape (Brassica napus L.). Weed Res., 27 31-34. 

Hall, J.C., M.J. Donnelly-Vanderloo, and D.J. Hume (1996). Triazine-resistant crops The agronomic impact and physiological consequences, pp. 107-126. In Duke, S.O. ed., Herbicide-Resistant Crops. Boca Raton, FL Lewis Publishers. 

Throughout western Canada and the central Great Plains of North America, volunteer wheat is becoming a more serious problem (Leeson el al., 2005). This may become a special concern if the volunteer wheat is glyphosate-resistant (Harker el al., 2005). There are also many examples of integration of traits from weeds into crops, and there is some evidence of spread from herbicide-resistant crops into weeds (Gressel, 2002). 

Nevertheless, more and more genetically modified varieties (mainly insect- and herbicide-resistant crops) become listed in the Common EU Catalogue of varieties, indicating that the cultivation of those GM varieties could accelerate in the near future. GM varieties need to be authorised in accordance with Directive 2001/18/EC (former 90/220/EEC) before they are included in this Common Catalogue and potentially marketed in the EU. By doing so, this directive intends to provide a freedom of choice between GM and non-GM products, not only for... 

In the herbicide market, more than USD 250 milHon of the sales of herbicides in the USA were transferred in 1998 from stand alone herbicides to herbicides that could be combined with a genetically modified crop. This redistribution of herbicides puts traditional agrochemical businesses at risk. Companies where herbicides account for more than 50 percent of the total revenues and that have a high market share in the USA are already suffering. The biggest short term losers are players that used to have strong sales in those areas (like soybean and com) where herbicide-resistant crops have been particularly successful. 

Most of the enzymes that catalyze the formation of xenobiotic conjugates in plants have not been well-studied. Since some conjugation reactions are involved in herbicide selectivity, it is likely that research relating to these enzymes will intensify as a result of efforts to develop herbicide resistant crops through bioengineering. Enzymes that may be useful in bioengineering for herbicide resistance are the GST enzymes, N-glucosyl transferases. 

This approach should be used to enhance herbicide selectivity in crop varieties, to avoid carry-over injury, for specific and limited special problems, and for minor acreage and high value crops. A major objective of developing herbicide resistant crops should be to provide more flexibility in control of resistant weeds. 

The risk of passing resistance genes from a crop to a wild related species is not inconceivable. A number of crops, (e.g., rice, millets, sorghum, oats, rapeseed, sugar beets, sunflower, alfalfa, peas, and potatoes) could be involved in introgression. Therefore, as herbicide resistant crops are engineered, a genetic barrier between crops and weeds must be devised. 

The development of herbicide-resistant crop varieties as undertaken by American Cyanamid is an evolutionary process that proceeds through a series of decision points. Initially, the market potential for herbicide resistance in the crop is evaluated. After a project is assessed as worthwhile, a scheme to make the crop resistant is established and implemented. Once the scheme proves successful and resistance is introduced into the crop of interest, the trait is characterized to assess commercial utility. A method for delivering resistant crops to the marketplace is then identified. Finally, through close cooperation between the seed company and the chemical company, the herbicide-resistant crop becomes available commercially. 

Herbicide resistant crops could serve to extend the life of patents or expand use of herbicides in some chemical markets. 

Chapter 5, entitled Safeners for Herbicides , demonstrates the progress in this research field, bringing out new compounds that create highly competitive products for the farmers out of only partly selective herbicides having a very broad weed spectrum and very low application rates ( the chemical answer to genetically modified herbicide resistant crops ). 

As mentioned previously, the planting of herbicide resistant crops worldwide. 

Shaner, D. L., Bascomb, N. F., Smith, W. Imidazolinone-resistant crops Selection, characterization, and management. In Herbicide Resistant Crops, Duke, S. O. (Ed), Lewis Publishers, Boca Raton, FL, 1996. 

R. Arias, M. D. Netherland, B. E. Scheffler, A. Puri, F. E. Dayan in Herbicide-resistant Crops from Biotechnology, Special Issue, S. Duke, N. Ragsdale (Eds.), Pest. Manag. Sci. 2005, 61, 258-268. 

The growing global use of GM crops has had several positive agronomic, economic, and environmental impacts. In the United States in 2004 alone, the use of GM crops reduced pesticide use by 62 million pounds, with 55.5 million pounds of that accounted for by the use of herbicide resistant crops. GM crops also produced significant environmental benefits. In addition to reduced pesticide use, increased no-till practices have reduced water runoff, greenhouse gas emissions,... 

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