Resistance to herbicides

The successful transfer of recombinant DNA into plants was vividly illustrated by an experiment in which the luciferase gene from fireflies was introduced into the cells of a tobacco plant (Fig. 9-29)—a favorite plant for transformation experiments because its cells are particularly easy to transform with Agrobacterium. The potential of this technology is not limited to the production of glow-in-the-dark plants, of course. The same approach has been used to produce crop plants that are resistant to herbicides, plant viruses, and insect pests (Fig. 9-30). Potential benefits include increased yields and less need for environmentally harmful agricultural chemicals. 

A more recent factor affecting weed management has been the introduction of crops genetically altered for tolerance or resistance to herbicides. The first herbicide-tolerant field com (IMI hybrid corn) was developed as a way to reduce the effects of carryover from imidazolinone and sulfonylurea herbicides applied to soybean in a corn-soybean rotation. These hybrids also soon found use in areas where triazine use was restricted. 

Ernst, D., E. Kiefer, M. Biihler, A. Bogenrieder, and H. Sandermann Jr. (1996). On the basis of atrazine resistance in weeds, pp. 56-58. In De Prado, R., J. Jorrin, L.G. Torres, and G. Marshall, eds., Proceedings of the International Symposium on Weed and Crop Resistance to Herbicides. Cordoba, Spain Graficas TYPO. 

Target site cross-resistance, in which a change at the site of action of one herbicide also confers resistance to herbicides from a different class (e.g., selection by triazine-resistant D1 protein that is also less sensitive to triazinones). 

Multiple-resistance is when more than one mechanism conferring resistance to herbicides in different chemical classes is active in an individual weed or population of weeds. Plants with multiple resistance may possess two or more distinct resistance mechanisms. Two grass species that display both cross- and multiple-resistance are rigid (or annual) ryegrass and blackgrass (Hall et al., 1994). 

Gasquez, J. (1995). Inheritance of herbicide resistance within weeds. In Proceedings of the International Symposium on Weed and Crop Resistance to Herbicides. Cordoba, Spain Cordobesa de Impresiones Graficas, p. 114. 

Gressel, J. and L.A. Segel (1978). The paucity of plants evolving genetic resistance to herbicides Possible reasons and implications. J. Theor. Biol., 75 349. 

Harper, J.L. (1956). The evolution of weeds in relation to resistance to herbicide. Proc. Brit. Weed Control Conf., 3 179-188. 

Christopher, J.T., S.B. Powles, J.A.M. Holtum, and D.R. Liljegren (1991). Cross-resistance to herbicides in annual ryegrass (Lolium rigi-dum) II Chlorsulfuron resistance involves a wheat-like detoxification system. Plant Physiol., 100 1036-1043. 

Padgette, S.R., X. Delannay, L.D. Bradshaw, B.H. Wells, and G. Kishore (1995). Development of glyphosate-tolerant crops and perspectives on the potential for weed resistance to glyphosate, p. 154. In De Prado, R., Garcia-Torres, L., and Jorrin, J., eds., International Symposium on Weed and Crop Resistance to Herbicides. Cardoba, Spain Cardobesa de Impresiones Graficas, SL. Abstract, 92. 

Other costs which were identified but not included in many of the studies, primarily because of the difficulty in quantifying their effect, are costs from increased weed resistance to herbicides replacing the triazines direct labor and management costs of developing and using new weed control practices and increased erosion damage costs, such as siltation of lakes, subsequent water recreation reduction, and lower land productivity. The economic impact due to weeds becoming resistant to the triazines was found to be minor. 

As it was mentioned, crops may be genetically engineered for weed management purposes by making them more resistant to herbicides or by improving their ability to... 

Herbicides comprise 60-70 percent of total usage of pesticides in developed countries. Plants develop resistance to herbicides which in turn demands altered management strategies through improved herbicides and/or herbicide mixtures. This may involve different modes of action, for short-term efficacy and long-term control to be effective. 

Weed Resistance to Herbicides Lessons Learned and Future Directions... 

Much has been learned over the past 30 years concerning weed resistance to herbicides. Some of the events that have occurred have been unexpected or have gone against conventional wisdom it is perhaps from these that we learn the most. 

The realistic view is that the first option will be most prevalent, the second option will be practiced by a minority of farmers (but may increase ), and the third will remain a very long-term hope. Regardless of the practicalities of these different scenarios, it must be recognised that weed resistance to herbicides has become firmly established in many... 

Powles SB., Yu Q. Evolution in action plants resistant to herbicides. Annual Review of Plant Biology 2010 61 317-347. 

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