Drought tolerance is the holy grail in crop improvement these days. We are running out of water; cannot easily expand irrigation; poorer farmers are affected most by it; and climate change will make things worse (etc.).
Breeding for drought tolerance has not been very successful. For lack of trying? Many years of work at CIMMYT seem to be paying off. Or is it just too damn difficult because of the multiple genes involved (from stomatal regulation to root growth), and the multiple droughts (when, how long, how much) to deal with.
Can biotech come to the rescue? This New York times article suggests that big companies and single genes may do the trick. I have to see it before I believe it, something like this picture, which shows drought-resistant corn on the right, tested next to “traditional” corn plants in Nebraska, USA. I want to see that picture in the fields of African farmers.
Or should farmers who cannot grow maize because of drought start thinking of another crop? Why not grow sorghum?
Is looking for single genes sometimes not a surrogate for real understanding? Breeding for drought tolerance in maize is perhaps one of the few areas where physiological insights have contributed to breeding success. Why all the fuss about single genes if we know what we want in phenotypic terms?
Hello,
First of all, I would like to congratulate Luigi and Jeremy for a very informative blog and also welcome Robert to this blog. To me it is a very informative blog both for reseach _and_ teaching.
Second, I have a question for Robert: I agree with his statement that we need to see the results in the field and I would add in multilocation, multiyear trials before we can decide what if an approach has worked. My question is therefore: what is the origin of the materials shown in the picture? Can you tell us more about their identify, how they were obtained, etc.
Thanks in advance,
Paul
@Paul Gepts – Thanks for your comment Professor Gepts. I can maybe answer before Robert comes back on line. The picture is from the New York Times article that Robert was referring to. The NYT credits the photograph to Monsanto.
Thanks Paul — I need to learn the ropes of clear blogging.
Thanks Jacob — I do not know if “looking for single genes is a surrogate for real understanding”. You still need to decide what gene function you are looking for, carefully screen plants, and so on. Perhaps that is not real understanding. I can live that if the drought tolerance is real.
Most of the time, when you are breeding on the basis of phenotype, you don’t have any understanding of what is going on at all. You take your best lines for a certain trait, breed them with each other or with other lines, and see what you get. If it works, you can turn it into a cultivar and release it. But in this process, there is no way to know what the underlying genetic reasons for this trait are, unless you follow up with research to them find the Quantitative Trait Loci, the many genes that affect the polygenic trait. That usually come after your breeding discovery.
When I say “real” I mean to say the understanding of the physiological mechanism(s) of drought tolerance, not its genetic basis. I agree that most genetic understanding in breeding comes after having identified the phenotype. The same is true for physiology, as breeders like Donald Duvick used to point out. Breeders can do very little with the wisdom of hindsight.
However, breeding for drought tolerance in maize is perhaps an exception as it has benefitted (I think) from physiological research. Deeper physiological understanding has enabled plant breeders to refine their search for traits (photosynthate partitioning, anthesis-silking interval, etc.). “Drought resistance genes” then sounds like a quite unspecific thing to look for.
I also disagree with when Robert says that breeding for drought tolerance in maize has not been very successful. The picture says otherwise!
Good points. “Robert says that breeding for drought tolerance in maize has not been very successful.” Did I say that? I did not mean to. I really need to take that on-line blogging course.
Interesting discussion. I do think there is a long-term benefit in knowing the genetic and physiological basis of a trait, especially more complex traits such as drought or quantitative disease resistance. Although the initial results may come after the first breeding results, subsequent breeding cycles will benefit from this understanding as well. This understanding will, for example, consist of the genetic architecture of the trait: how many genes, magnitude of the effect of the genes, linkage relationships, etc. An additional benefit is the development of markers tagging these genes. This information will benefit subsequent breeding cycles in which breederst attempt to “pyramid” several genes. An example of this approach is the high level of resistance to common bacterial blight obtained by bean breeders over the course of several years (Miklas et al. 2006. Euphytica 147:106-131). Initially, resistance to common bacterial blight was considered to be a difficult disease to breed for. Yet, identification of major QTLs in different sources has helped – in part – bean breeders to raise resistance to this disease from 6-8 to 1-2 (on a scale of 9 susceptible to 1 resistant).
The other comment I would like to make is that we need to have more information about the nature of the materials shown in the maize picture. Apparently it shows a successful attempt at breeding for drought tolerance. I have the following questions:
a) How are the materials to the left and the right related, if at all? Do they show “before and after”?
b) What was the improvement method used? Genetic engineering? What gene(s)? Classical breeding also involved?
c) What was the field experimental design? Was this a rainfed experiment? What was the level of water stress?
It seems to me that we should make a diagnosis on more than just a photo!
There’s a Monsanto press release that features the identical photo used by the NYT.
a) Left and right are “corn with the drought tolerant gene (on right) and control hybrid (on left)”.
b) Genetic Engineering. Don’t know what genes, but you can probably find out from the release and some of the links it contains.
c) Ditto.
Yeah it would be good to know whether the two corn lines are otherwise isogenic. Can we consider it a confirmation of the trait they developed, or is this a picture of good and bad corn in a random field that they thought might make an eye-catching press release photo?
There is not much detail on the Monsanto website. There are some slides though. The same photo is there, but now with the lines labeled as “Control hybrid (76 BU/AC)” and “With gene (94 BU/AC)”.
There are also graphs that show yield advantages of drought tolerant lines that range between 7 and 15%. Monsanto expects these lines to produce 8-10% more in drought stress environments or save 100 $ per acre or more in irrigation costs.
Wait a minute. 0n the photo we are talking 90-100% yield difference. Apparently it is not very representative of drought tolerance benefits of these new maize lines. What strikes me about the photo is that the leaves are dark green on both sides. If the plants look equally healthy, why does the control not have any grain? Did it recover from a dramatic early drought? Or are there no seeds because of sterility induced by drought during flowering?
BU/AC means bushels per acre in this case, so I would assume that this is likely to a more dramatic photo than the average difference in yields. Heck, it could even be that the plants on the dividing line were dramatic and this was just about the only shot they could get (not as likely).
Here’s an interesting question, though, how does this photo compare to the obviously doctored photo of conventionally-bred purple-ish tomatoes in this post?
Anyway, I would think that the numbers are better information than the picture, but it does catch one’s eye.
Yeah, the picture is suspicious and a chopped up version of it even appears here. However, the Science feature also provides a clue to the genetic makeup of the transgene in question (including the compared hybrid) and it seems the evil empire has published the whole damn genetic engineering-, breeding- and field testing- process in the public domain. Magic bullet, ok, but if its only a CSR hype they’ve sure invested some pretty impressive science in it.
The picture looked like an example of grain abortion to me.
The PNAS article says that they tested for drought during flowering in a field experiment.
Still very little information about physiology (that I could understand) in the PNAS article, however.
Thanks Inocoluted Mind, so BU/AC = Bushel per acre. For non-Americans that would be 5111 vs. 6233 kg/ha then; and a whopping 24% higher either way.
Thanks Ola, those articles do help a lot. So the drought tolerance is from a maize equivalent to an Arabidopsis gene.
And, Jacob, in the Science News item there is even mention of the need to “dial into the physiology of the plant” with drought tolerance; unlike Bt, that works like “flipping a switch”.
I’m not sure, but I think I used to work with someone who was trying out that arabidopsis gene in tomato. I know it was from arabidopsis, and I know it was drought tolerance, but I’m just not sure if it was that gene. It did give some promising results, though, I should check up on it…