More maybe GM yield gains

April 2013

Maize/corn field in USA. Photo by Lars Plougmann (originally posted to Flickr as In the corn field)
[CC-BY-SA-2.0 (], via Wikimedia Commons
Arpad Pusztai has suggested we distinguish between 'science' (the search for truth through like-for-like comparisons) and 'commercial research' (the search for profit). A recent example in the published literature illustrated this nicely (see TURNING A GM YIELD LOSS INTO A GAIN - April 2013).

Here's another one...

Just published in the journal Crop Science, is a paper entitled “Transgenic Corn Rootworm Protection Increases Grain Yield and Nitrogen Use of Maize”.

COMMENT - This seems self-explanatory: it says quite clearly what was studied and what was found.

The abstract indicates that:
  • two transgenic triple-stacked hybrids were compared with their “near-isogenic non-Bt Roundup Ready corn 2 (RR2) counterparts” during two consecutive years of cropping
Note. If you know your GM maizes, you'd realise that the test crop was stacked with a Bt gene for Corn Rootworm (CRW), a Bt gene for European Corn Borer (ECB) and a gene for Roundup herbicide tolerance.
  • there was “minimal CRW feeding pressure on the roots“
  • during one of the two years, the overall average grain yield and the ability to respond to nitrogen fertilizer increased due to the Bt trait for CRW resistance
  • in conclusion, CRW protection “has supplemental agronomic benefits”
The brief summary in the abstract raises questions about how 'scientific' this study really was: when the information is expanded in the body of the paper, the questions get bigger too.

For example, only the CRW trait is mentioned as a variable which could influence yield. The ECB trait is a second unmentioned variable in the triple-stacked crop which could affect yield. The Roundup Ready comparator crop was protected using soil-applied insecticide, which introduces another variable into the study in regard to root function and root-soil ecology which could affect yield. The Roundup Ready plants not only had no Bt protein, but presumably also accumulated Roundup; that's yet another uncontrolled variable which could affect yield.

For example, the CRW root damage was only measured during one out of the two years of the study, and the yield increase seems obvious in only one of the triple-stacked hybrids, also better nitrogen use was only significant in one of the two years. Two readings giving divergent results aren't very useful: are we seeing a 'chance' improvement or a 'chance' disimprovement in performance? Science is based on at least three measurements to make trends clear and avoid this type of doubt. In our previous illustration of commercial research, similar triple-stacked GM maize observed 3,2015 times in the University of Wisconsin trials gave a mean yield of 1.57 bushels per acre less than its conventional counterparts. It seems that the smaller study may well be a case of 'chance' improvement because its findings aren't born out by the bigger one.
For example, the “near-isogenic counterpart” (i.e. the truest scientific control crop) was, in reality an RR maize marketed by a seed supplier as having the same genetic background and similar characteristics and agricultural qualities. The “isogenic” part was never confirmed.

COMMENT - After reading the examples above, does the title seem quite so self-explanatory? Did it really study the effect of CRW transgenic protection? Did it really identify an increase in yield? Or was there really really evidence of better nitrogen efficiency use?

The conclusion of “supplemental” agronomic benefits attributed to CRW-resistance genes in the abstract is expanded by the end of the paper into agronomic benefits that extend beyond insect control, and even go on to “support the role of biotechnology in promoting sustainable and resource use efficient maize production to feed a growing world population”.



That's a big conclusion to come from two readings of non-validated test material in a study with four uncontrolled variables.

Was it 'science'? No

Was it useful commercial research? Probably, because the nitrogen use efficiency tests suggest that farmers may be applying more nitrogen fertilizer than is necessary on some kinds of GM crop. It also indicates that farmers and regulators should be demanding that the biotech industry ascertain optimum fertilizers for each and every novel crop on a case-by-case basis before it comes to market.

Ominously, the authors' comment that their results “suggest a role for plant breeding in selectively improving genetic backgrounds for the desired agronomic responses to a biotech insect protection trait.” Does this mean that the plant breeders of the future will spend all their resources trying to tailor the plants to fit their artificial genes?

To put the research in another, possibly clearer, perspective, it was “supported in part by a gift from Monsanto Company”.

  • Haegele and Below, Transgenic Corn Rootworm Protection Increases Grain Yield and Nitrogen Use of Maize, Crop Science 53, March-April 2013
  • Benefits of Bt Corn Go Beyond Rootworm Resistance, Science Daily, 6.02.13

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