Transgenic Crops for Herbicide Resistance

A year after the introduction of the first commercial transgenic crop (Flavr SavrTM tomato with a longer shelf life) in 1994, transgenic, herbicide-resistant crops (HRCs) were introduced (Table 3.1) with the introduction of bromoxynil(3,5dibromo-4-hydroxybenzonitrile) resistant cotton and glufosinate[2-amino-4(hydroxymethylphosphinyl)butanoic acid] resistant canola. Bromoxynil resistance had little market penetration during the years when it was available. The next year, 1996, marked the introduction of the first glyphosate[TV-(phosphonomethyl) glycine] resistant (GR) crop (soybean). Other GR and glufosinate-resistant crops were introduced in the subsequent years. GR crops now represent well over 80% of all transgenic crops grown worldwide (James 2008). Accordingly, this chapter will deal primarily with GR crops. Several reviews (e.g., Duke 2005; Duke and Cerdeira 2005; Cerdeira and Duke 2006) and two books (McClean and Evans 1995; Duke 1996) are available on the topic of HRCs, but this rapidly evolving topic requires timely updates. Before the advent of transgenic crops, there was both controversy and optimism about their potential impact on farming, human health, and the environment (e.g., Goldberg et al. 1990; Duke et al. 1991). We have now (early 2009) had 14 years of experience with HRCs over vast areas in many parts of the world, providing a wealth of information on the utilization of this technology, as well as the impacts of HRCs on the environment. This review will deal, in part, with these topics as they apply to HRCs