Roundup Ready 2 Yield as much as Conventional Soybeans?

Jonathan Latham and Allison Wilson

Gore Vidal once wrote that “I told you so,” was the most satisfying sentence in the English language. If so, then the imminent launch of Monsanto’s Roundup Ready 2 Yield soybean line is going to provide a lot of satisfaction, though not to supporters of Monsanto. The role of the new glyphosate-resistant line (insertion event MON88978) in the following story is to provide a single, but highly significant, new data point.

Roundup Ready 2 Yield will supercede Monsanto’s original Roundup Ready transgenic soybean (event 40-3-2) and yet it confers the exact same trait and contains the exact same gene as Roundup Ready. So why would Monsanto feel the need, probably at substantial cost, to replace the original Roundup Ready? A big clue, along with the advertising, is the name. Monsanto claims that Roundup Ready 2 Yield produces a 7-11% superior yield than the original Roundup Ready, which ought to be rather surprising since herbicide resistance is not a yield trait. But the answer is in fact simple: Roundup Ready 2 Yield is an admission that the original Roundup Ready had a major yield drag, one of several unanticipated consequences of this insertion event.

What we argued

Many groups and individuals have argued that transgenic plants may be prone to unanticipated consequences, either due to pleiotropy or to effects of transgene insertion (Schubert 2002). Our review papers on the molecular characteristics of transgene insertion sites and the associated genetic consequences of plant transformation techniques provided the first, and still only, review of the mutagenic nature of plant transformation and the consequences for the biosafety of transgenic plants (Wilson et al. 2006; Latham et al. 2006).

Our analysis reached two principal conclusions. The first was that transgene insertions, especially those resulting from particle bombardment, are frequently complex and frequently disruptive, often of multiple coding regions. Secondly, current plant transformation techniques are typically associated with very large numbers of mutations, some of which will inevitably be closely linked to the transgene and therefore hard to separate genetically. Based on these observations we speculated that unanticipated phenotypic consequences were likely to be associated with transgenic plants, and furthermore, that these would sometimes be deleterious or otherwise harmful (see Nature Biotechnology correspondence Bradford et al. 2005; Wilson et al. 2006; Latham et al. 2006).

At the time, a frequent response from regulators, and others, was that, nevertheless, transgene insertion sites and/or linked mutations, were unlikely to result in phenotypic consequences of any significance. This point has been argued in print by Bradford et al. (2005), Altpeter et al. (2005) and Schouten and Jacobsen (2007).

The unanticipated traits of Roundup Ready soybean (event 40-3-2)

Launched in 1996, Roundup Ready soybeans, which express an enol pyruvate shikimate-3-phosphate synthase (EPSPS) gene from the microbe Agrobacterium tumefaciens (and contain no other transgenes), have been an undoubted commercial success. However, they have been controversial, both because of complaints from farmers and because of revelations of unanticipated physiological consequences. These have included stem splitting and probably lignin overproduction (Coghlan, 1999; Gertz and Vencill 1999), small seed size and a yield drag (Elmore et al. 2001; Nelson et al. 2002; Benbrook 1999; Gordon 2007), and last but certainly not least, a significant manganese (Mn) deficiency (Gordon 2007).

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