Roundup Ready 2 Yield as much as Conventional Soybeans?

Two powerful arguments together suggest that of these unanticipated traits, the manganese deficiency and the yield drag, are caused specifically by the 40-3-2 insertion event, which is contained in all current commercial Roundup Ready soybeans. First, even though the 40-3-2 insertion event has been backcrossed into hundreds of soybean cultivars, Monsanto has consistently failed to separate the unanticipated traits from the transgene, suggesting that they are extremely closely linked to, or inseparable from, the actual site of insertion. This fact alone still allows, however, the possibility that the action of the EPSPS protein might be responsible for the unanticipated traits. The introduction of Roundup Ready 2 Yield, however, suggests that this is not the case. Although Roundup Ready 2 Yield contains different transgene promoter and termination sequences from Roundup Ready, the transgene product, the bacterial EPSPS protein, is identical in sequence (USDA petition 06-178-01p). Nevertheless, according to the same petition, Roundup Ready 2 Yield yields 7-11% over Roundup Ready, which just happens to approximate to the yield penalty that researchers have suggested Roundup Ready confers.

The learning curve

In principle, much could be learned from this story. The first, and perhaps the most significant, is to lay to rest the notion that unintended traits in transgenic plants are invariably unimportant and rare. Not only is 95% of the soybean crop of the United States currently yielding 7-11% less than it should, Roundup Ready soybeans can contain less than 40% of the Mn contained in isogenic lines (Gordon, 2007). Neither of these traits can reasonably be called insignificant.

Secondly, the original petition for Roundup Ready soybeans inadequately analysed the transgenic line prior to commercial approval. As was subsequently shown, the 40-3-2 insertion site of Roundup Ready had a complex and scrambled insertion site and a non-functional transcription termination sequence, which allowed aberrant transcripts to transcribe beyond the transgene and into scrambled DNA (Hernandez et al. 2003; Rang et al. 2005; Wilson et al. 2006). Additionally, the compositional and phenotypic analyses, which were supposed to demonstrate the identity of Roundup Ready to conventional soybeans, omitted important data points. Thus, the petition failed entirely to detect a deficiency in a major nutrient (Mn) as well as the assorted agronomic defects of Roundup Ready soybeans. Attention to any one of these data gaps might have alerted regulators to the problems.

Now available for public inspection is the Monsanto petition for Roundup Ready 2 Yield (USDA petition 06-178-01p). Monsanto, it appears, has learned from some of the mistakes of Roundup Ready. They have replaced the nos terminator, they have also avoided callus culture and instead used meristem culture, which should be much less mutagenic, and also transformed this time with Agrobacterium tumefaciens rather than particle bombardment.

For regulators, however, the learning curve is conspicuous by its absence. Regulators in the USA, the EU and China, as well as elsewhere have already approved Roundup Ready 2 Yield, even though the petition is again flawed. The petition again fails to present a DNA sequence for the insertion site or to analyse DNA flanking the insertion site; it fails to search for aberrant mRNA transcripts; and perhaps most remarkably, its compositional analysis fails to measure even a single mineral nutrient.

Of particular interest to us, the petition also demonstrates that the new Roundup Ready 2 Yield soybean has its own unanticipated plant trait: Roundup Ready 2 Yield plants are consistently 5% shorter than isogenic lines. Evidently, the regulators who have approved Roundup Ready 2 Yield (including the famously ‘stringent’ EU) have agreed with Monsanto’s conclusion that there is “no biological meaning” to this difference (USDA petition 06-178-01p). To us, however, this difference has, in fact, two biological meanings. On a practical level, as any farmer could have pointed out, crop stature is an important agronomic trait: as well as being typically an important weed suppression character; plant stature is important in mechanical harvesting; and also for disease susceptibility, where ground contact and foliage positioning affect in-crop humidity. Secondly, many commercial transgenic crops have unanticipated traits compared to their isogenic lines (e.g. Colyer et al. 2000; Escher et al. 2000; Brodie 2003; Poerschmann et al. 2005; Herrero et al. 2007). Unlike these, however, Roundup Ready 2 Yield used the best available plant transformation methods, yet still has at least one unanticipated trait.

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