Herbicide Resistant Soybeans

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. 

The development of herbicide-resistant weeds has also been an influence on the selection of herbicides used on field corn or soybean. Weed resistance now affects nearly every decision a farmer makes about herbicide selection either a farmer is trying to control resistant weeds or is selecting herbicides that may reduce the possibility of weed populations becoming resistant. The adoption of the imidazolinone- and sulfonylurea-tolerant com hybrids mentioned above was in part a response to the presence of atrazine-tolerant pigweeds or kochia in many fields. However, a recent decrease in die use of imidazolinone and sulfonylurea herbicides can also be attributed to the development of populations of weeds that have become resistant to these herbicides. 

Weeds are rapidly becoming resistant to some of the newer herbicides, and it is important to realize the consequences. For example, in Missouri, Bader et al. (1995) conducted a study on corn-soybean rotations in which they used only ALS-inhibitor herbicides, that is, imazethapyr in soybean and primisulfuron-methyl in corn. Within 4 years, a common waterhemp biotype resistant to 5-fold higher rates of ALS inhibitors was flourishing. Greenhouse tests confirmed that ALS-resistant common waterhemp biotypes were present in several plots in the experiment. Within the same state, Bader et al. (1994) reported one case of atrazine-resistant common waterhemp, which developed where a farmer grew continuous com and used only atrazine for more than 10 years. Table 11.1 shows trends in the numbers of herbicide-resistant weeds. 

Owen, M.D.K. (2001). World maize/soybean and herbicide resistance. In Powles, S.B. and Shaner, D.L., eds., Herbicide Resistance and World Grains, Boca Raton, FL CRC Press, pp. 101-163. 

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. 

The advantage for the farmer is that he needs only one product, instead of several different selective (and more expensive) herbicides. Roundup ready soybeans were launched in 1996 and today 50 percent of the soybean crop in the United States is derived from roundup ready seeds. Other glyphosate-resistant transgenic crops introduced by Monsanto are maize and oil seed rape. Competing companies also developed herbicide-resistant plants or plants genetically modified to be protected against certain pests, but none has achieved a commercial breakthrough, mainly because of political reasons. 

New introductions, including herbicide-resistant canola, virus-resistant papaya, and other food crops, have been accepted. Soybean producing an oil containing the co-3 fatty acid stearidonate has been developed for the nutraceutical and fish farm feed market [3]. Interestingly, the earliest genetically engineered oilseed crop was... 

U.S., 90% of soybeans are genetically transformed to be herbicide-resistant 80% of cotton is transformed for resistance to herbicides and, through incorporation of Bacillus thuriengensis, to various insect pests and 50% of field corn is similarly modified for both herbicide and insect resistance [4], None of the crops are used directly for human food, although food use is made of corn and cottonseed oil from genetically modified corn and cotton and the bulk of the transformed soybeans and corn, and cottonseed meal, are fed to animals which enter the human food supply. End-user and consumer nonacceptance of genetically modified foods continues in many quarters. 

Over 90 percent of this acreage was planted with either herbicide-resistant (71 percent) or Bt (Bacillus thuringiensis) insect-resistant (28 percent) crops. Most GM crops have been planted in industrialized nations, with the United States accounting for nearly three-quarters of the total. Herbicide-resistant soybeans were the most commonly planted GM... 

In 2005, GM crops were cultivated in 21 countries with 71% of those acres being accounted for by herbicide resistant traits in soybean, corn, canola, and cotton. This percentage increases to 82% if one includes herbicide resistance trait acres that are stacked with other biotechnology traits. Globally, GM herbicide resistant soybean, cotton, canola, and corn were grown on 134.4 (60%), 12.1 (14%), 11.4 (18%), and 24.5 (7%) million acres, respectively. (Fig. 6.1.1) [1]. 

This section includes data for herbicide resistant crops generated by both selection and biotechnology processes. The first commercially available herbicide resistant crop in the United States was imidazolinone resistant corn introduced in 1992. This was followed by glyphosate resistant soybean and canola in 1996. 

Fig. 6.1.2. Percentage of total acres of herbicide resistant soybeans by trait. The value given for 2005 is a forecast.

There are two commercially available herbicide resistant traits in soybean, glypho-sate resistance (Roundup Ready , RR) and sulfonylurea resistance (STS ). Herbicide resistance now accounts for over 90% of approximately 73 million total soybean acres grown in the United States (Fig. 6.1.2) [6]. 

As with soybean, the adoption of herbicide resistant cotton has resulted in significant grower and environmental benefits. Use of these traits in 2004 alone has resulted in a reduction in crop production costs of 264 million and pesticide use of 14 million pounds. A major effect of herbicide resistant cotton has been the increase in the adoption of no-tUl production. The percent increase in no-till acres has been higher in cotton than any other crop and resulted in about 20 per acre savings in fuel and labor costs [2]. 

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