Glyphosate tolerance

Transgenic soybean plants expressing the CTP-CP4 EPSPS display commercial levels of Roundup tolerance. These results vaUdate the importance of substrate kinetics of EPSPS in order to maintain adequate rates of aromatic biosynthesis. Furthermore, the fact that glyphosate tolerance can be obtained by expression of a glyphosate-tolerant EPSPS illustrates that the herbicidal mode of action of glyphosate is related solely to inhibition of the EPSPS reaction. 

Anon., Glyphosate tolerances for residues, Fed. Regist., 44, 5136, 1979. (CA90 136358p)... 

Plant extract gums, 13 63t Plant extracts, as antioxidants, 12 61 Plant fireproofing, 21 841—842 Plant genetic engineering, 12 484-496 bioengineering of glyphosate tolerance, 12 487-490... 

Other bacterial mutants, such as a mutant Escherichia coli enzyme tolerant to glyphosate, have been described (47). The E. coli mutant had a single amino acid change from the wild type, resulting in substitution of glycine 96 with alanine. An identical mutation was reported in glyphosate-tolerant Klebsiella pneumoniae (48). The nature of changes in the kinetic constants of the K pneumoniae enzyme is similar to that of the E. coli enzyme. 

With the culture of soybean and field com so intimately intertwined throughout the Midwest, changes in soybean weed control affect com weed control as well. One real effect of the widespread adoption of glyphosate-tolerant varieties has been the disincentive to discover and develop new products and new chemistries. Since the advent of glyphosate-resistant soybean, very few products have been developed for that market. 

About 80% of soybean planted in the United States in 2003 was glyphosate-tolerant soybean, treated with only glyphosate for weed control. In addition, more acres of corn are expected to be glyphosate-tolerant over the next years. 

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. 

Strandberg, B., and M. B. Pederson. 2002. Biodiversity in Glyphosate Tolerant Fodder Beet Fields. Silkeborg National Environmental Research Institute. 

Figure 12. HG-2 glyphosate tolerant alfalfa derived from tissue culture selection. A. Abnormal multifoliate leaf structure. B. Abnormal flower morphology.

For herbicide (glyphosate) tolerant soybean, it is noted that adoption concurs with a background trend towards post-emergence herbicide applications from 1990-1995 [7]. Glyphosate (a.o. sold as Roundup) can be used post emergence over the top of the herbicide tolerant soybean crops. As a broad spectram herbicide it affords protection against a wide variety of aimual and perennial weeds, including the difficult-to-control water-... 

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