I was talking to Greg Edmeades tonight. Our conversation coalesced on the topics of the recent posts on maize water stress tolerance and on the usefulness of engineering purple tomatoes.
For many years, Greg led the maize crop physiology group at CIMMYT. He says that one of the main reasons for their success with drought tolerance is their long term institutional commitment to it: 35 years and counting. A particularly impressive feat is the widespread adoption of their maize varieties in southern Africa. For example, ZM623, selected from South African parents by Marianna Bänziger, is grown on about a million ha, says Edmeades.
His take on biotech for drought tolerance is, sure, “use whatever works, but if you are an African agricultural research institute, then, why bother?” Monsanto is reporting 10-15% yield increase under drought stress, and says it will make their technology freely available for use in Africa. Edmeades reckons that you can get a similar yield increase in about 7 years of conventional breeding and selection. And less when using molecular markers. If that is the case, it may not be worth it to deal with the complexities of genetic engineering.
Unless, perhaps, the approaches are entirely additive and you get a combined yield benefit of 30%. I think that’s unlikely. Drought tolerance is about making best use of the available water. It does not increase the amount of water.
Later:
Greg told me that I had been a little harsh in suggesting that he would not advise national programs in Africa to use a transgenic approach to drought tolerance. He would only advice against transgenes if “they had access to a steady stream of good germplasm improved for drought tolerance, and there was no regulatory framework for transgenes in place in that country. If regulatory frameworks exist, and there is no facility of improving their own varieties (or newly released commercial varieties) for drought tolerance in a systematic way, then certainly I’d take the transgenic option, especially since it is being offered on a royalty free basis.”
Well it may not be completely additive, but still give a higher yield in combination. It could be more like 28% or 26%, still an improvement which would have a large effect on a large number of acres.
Which approach is used where should depend upon multiple factors, including and especially how effective it will be.
But here’s a thought about the breeding approach vs the GE approach – are they achieving the exact same kind of trait? What I mean is, do the CIMMYT drought-tolerant varieties of maize perform as well as modern varieties under ideal conditions, or do the water-saving traits limit the growth of the plant, even when growing conditions are good?
From my understanding of the GE approach described, weren’t they trying to get a plant that would be competitive when the conditions are wet and wild, but then also out-perform other maize varieties when conditions are dry?
In my understanding, drought-tolerant varieties obtained with classical breeding techniques by CIMMYT and partner institutions don’t perform worse under wet conditions and sometimes even better than other modern varieties. Much of it is about photosynthate partitioning between grains and pollen. Improving this is also beneficial under wetter conditions.
I find it very difficult to tell from the PNAS article whether Monsanto actually achieved something that is complementary to classical breeding work. The same physiological traits may have been achieved by other means (genes). Or does the gene expression work really exclude this possibility?