NIAB - National Institute of Agricultural Botany

Orson's Oracle

Look before you leap!

Posted on 07/06/2012 by Jim Orson

I have great sympathy with those trying to introduce new crop technologies, which may help us in the challenge to better secure future food supplies.

Take the first halting steps to introduce GM into Europe. Inevitably, the easier to achieve GMs were introduced first; that’s the way with technical developments. GM herbicide tolerant crops offer good and reliable weed control, something for which herbicide manufacturers have been striving over the last few decades.

Not only is weed control in GM herbicide tolerant crops reliable but it offers the real possibility of adopting rational weed control strategies. The grower can check the emerged weed population before application and make an assessment on the risk posedOilseed rape in flower to current and future crops. An application may not be necessary or a lower dose could be used. In most cases, ‘conventional’ herbicide strategies don’t offer this option: weeds have to be controlled before or very soon after they emerge.

However, the potential weed control offered by this technology may be too high in some crops to be acceptable under the EU GM legislation, because it may result in an indirect reduction in the soil weed seedbank. This is deemed a threat to biodiversity in the future. Fancy - a conventional herbicide being banned because it was too effective!

I think that the whole industry is beginning to accept that we need to mitigate the level of weed control now being achieved in the field by encouraging biodiversity on specifically managed areas on the farm. So we could mitigate the impact of the higher levels of weed control possible with GM herbicide tolerant crops. But it is worth pointing out that sympathetically managed herbicide regimes in these GM crops can lead to better within crop biodiversity with no, or very little, threat to the current or future crops.

Part of the anti-GM rhetoric is that the technology is not that special and conventional breeding linked to better knowledge of genomics will result in the same thing. And that’s what has happened with the oilseed rape ‘Clearfield’ varieties tolerant to the imidazilinone herbicides being introduced into Europe.

But now there are campaigners attacking trials containing these varieties complaining that this is GM by the back door! It proves some of those who campaign against GM don’t want any new approaches to food production, but it is also clear that some pine for a return of a rural idyll of small-scale farmers using traditional techniques and cannot see past this point. We may be all right in our rural idyll but outside it more food will have to be produced, possibly with huge environmental implications.

The future is going to get even more complicated. Biotech is opening up other new plant breeding methods and genetic innovation. It is now possible to use GM as part of the process but the final product may not have a GM fingerprint. This is a challenge to regulators if it’s decided that there should be regulations to take into account what is now possible. And in the meantime further new breeding methods will be developed so ‘future proofing’ any new regulations will be a huge challenge.

All novel approaches to crop production need to be considered with care. The ‘imi’ tolerant oilseed rape is a case in point. It offers control of weeds closely related to oilseed rape, namely charlock and runch. It also controls conventional rape volunteers; a very valuable aid to maintaining crop quality. This could be particularly useful in protecting the quality of the high oleic, low linolenic varieties. Of course, this could be the one and only opportunity. The volunteers of ‘imi’ tolerant oilseed rape will be resistant to ALS-inhibitor herbicides.

However, its introduction has to be thought through. The mode of action of the imidazilinone herbicides is ALS inhibition - a very common mode of action with resistance in common poppy, common chickweed and scentless mayweed as well as black-grass. Using an ‘imi’ herbicide in oilseed rape means less reliance on this mode of action elsewhere in the rotation. This will be helped by volunteers on ‘imi’ tolerant oilseed rape being resistant to ALS-inhibitor herbicides.

However, there is one situation that has to be thought through with particular care. Debut, an ALS-inhibitor herbicide, controls oilseed rape volunteers in sugar beet. It enables these two crops to be grown in the same rotation and this may no longer be possible with ‘imi’ tolerant oilseed rape.


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