There is a puzzling paragraph in the latest issue of The Economist. Well actually there’s a lot of puzzling paragraphs in the latest Economist, but the one I’m talking about is not in the finance or economics sections. And it is puzzling not so much because of what it says, but because of what it leaves out. Here it is in full. It appears in an article on the effect of climate change on developing countries.
This kind of increasing unpredictability would be dire news at the best of times: hit by drought and flood, the land becomes less productive. It is compounded by another problem. The higher-yielding, pest-resistant seed varieties invented in the 1960s were designed to thrive in stable climes. Old-fashioned seeds are actually better at dealing with variable weather—but are now less widely used. Reinstituting their use will mean less food.
What follows is a long paragraph which starts by saying that “[i]n India the gains from the Green Revolution are already shrinking because of local pollution, global warming and waning resistance to pests and disease…” and ends by quoting a World Bank study to the effect that because of climate change and population growth agricultural productivity will have to rise by 1.8% per annum for the foreseeable future. But there’s nothing in between, or indeed anywhere else in the article, about the importance of plant breeding in ensuring that increased productivity.
Now, many people see the value of moving landraces (or “old-fashioned seeds,” if you must) around, in particular from hot places to ones which are not so hot now but will soon be, for evaluation purposes — and more. And there may be some sense in which landraces are “better at dealing with variable weather” than modern varieties. But I don’t think anyone is seriously contemplating “reinstituting their use” on a massive scale in an effort to adapt agriculture to climate change.
What is needed — and urgently — if adaptation is to have much of a chance is effective breeding programmes, and landraces will be one of the sources of genetic material that these programmes will require, along with crop wild relatives and others. Shame The Economist didn’t say that more clearly.
Just to make sure I understand the idea – modern inbreds and hybrids obviously have reduced genetic variability so the same hybrid year after year won’t be able to react to climate change. Landraces have more genetic variability so the same landrace year after year will undergo natural and artificial selection and be able to react to climate change.
However, aren’t seed companies big and small producing new inbreds and new hybrids all the time? I’ve been told by plant breeders that commercial hybrids last about 5 years or less (at least in maize). Perhaps India doesn’t have enough plant breeding companies, but if that is the case, perhaps they need an ARS.
What do people like this Economist author think? That plant breeders developed these lines in the ’60s then have been resting on their laurels ever since?
“The varieties of the 1960s were designed to thrive in stable climes. Old-fashioned seeds are actually better at dealing with variable weather”.
Really? Where did they get that idea? Wasn’t it in those days that a farmer’s son from Iowa developed daylength insensitive wheat varieties that could grow all over the place?
Generalization comes at a price, but if I had to, I’d say the opposite is closer to the truth: landraces are more likely to be locally adapted (at least that is what I am often told is so good about them) and hence cannot tolerate variable weather as much as modern varieties can.
All right, as Anastasia points out, if you have a land race that is in fact a diverse population, and a sexually propagated out-breeder, it would likely co-evolve. But that is not an argument against the new varieties. Rather, it suggests that it could be beneficial to have a diverse set of them (or indeed some half-way decent seed companies).
I think the key thing here is to separate adapted from adaptability. Modern varieties are often described as widely adapted, meaning that they can grow in different places, often with the help of external inputs to make nutrients and water more similar across places.
Landraces are more adaptable, meaning that they contain the genetic diversity that permits natural and artificial selection to change their make up. The same diversity may make them less variable year on year.
Genetic diversity is not equal to being adaptable. Selection needs to work on that diversity to mold it to the new conditions.
Under farmer conditions, (semi-natural) selection sometimes leads to the “wrong” outcomes. A nice example is selection for drought tolerance in maize. Natural selection will lead to maize plants that invest more in pollen than in grain. From an evolutionary perspective this is a good strategy, but not for grain productivity. You need formal plant breeding to select for plants that invest in grain under dry conditions. Plant breeding is “counter-evolutionary” here.
Nobody considers the opposite conclusion that one might draw: having much genetic diversity might mean that selection hasn’t been very effective in the past.
Well, not all selection necessarily leads to a narrowing of genetic diversity.
Selecting implies discarding.
Yes, but.
If disruptive selection is taking place, would those “extreme” genotypes all be in the same field?
I don’t know whether your example of selection for more pollen production under drought conditions is observed or a thought experiment. Either way, it is a prime example of Ford Denison’s point that almost every case of artificial selection leading to enhanced agricultural production is effectively group selection. Imagine the fitness of a single dwarf wheat plant in a field of tall neighbours.
And having much genetic diversity might be the result of selection for adaptability and resilience. Here I think you are confusing the effectiveness of selection for the strength of selection.
Observed for maize.
Group selection: except that breeders don’t do group selection to breed drought-tolerant maize. They select individual plants with traits that give a higher group fitness. A subtle difference.
Selection for adaptability and resilience: selection of what?
Can you unpack the subtle difference for me please?
The selected individual performs well only when surrounded by similar individuals. An extreme form of density dependent selection, if you like, and one that is drifting far from the original topic, but what remains is that the selected individual would be outcompeted in pure fitness terms — not in terms of grain yield — when in a population of unselected individuals, say the ancestral population.
What’s the problem with selecting among populations for a phenotypic expression of stability of yield?
Group selection in evolutionary theory implies the whole group is the unit of selection. You reason from the outcome (a more fit “group”) back to the mechanism (“group selection”). But groups were never the unit of selection. Maize breeders select for individual plant traits in my example, so the individual plant is the unit of selection, not the group.
So you’re question is wrong: they are not selecting “among populations” but within populations.
And farmers and/or natural selection are NOT selecting within maize populations for drought resistance, they select for the most competitive plants. Also, group selection will have little effect, as under farmer conditions all populations undergo the same selection pressure for competitiveness. So in spite of their higher diversity, within and among populations, maize landraces will never end up as drought tolerant as modern maize varieties.
Ergo, plant breeding is needed to adapt to climate change.
Are landraces more adaptable than bred varieties? I’ll give my conclusions from one crop — 13 years of breeding cassava. We found that landraces are almost always (some exceptions) rather narrowly adapted. They fit the niches where they evolved. Taken to other ecosystems, they are usually susceptible to one problem or another — often several. We were able to develop more adaptable, and more broadly adapted, materials by using a broad genetic base and selecting under multi-location, difficult conditions of low soil fertility, no irrigation and no artificial pest or disease control. I think the same could be done for almost any crop. It’s usually not so much a matter of the inherent adaptability of individual landraces that limits or expands the possibilities in the bred materials, as it is the breeding methodology.
That’s a very good point, Clair.
To my knowledge, this is how corn and soybeans varieties in the US are developed as well. Start with a diverse germplasm base, then plant out the trials in multiple locations. The lines that do well in all or most locations will be continued, while the ones that have local adaptability only may be discarded. This is good for farmers because they know the crops will do well under more diverse conditions than a line that’s adapted for only one set of climatic conditions, but it can be overdone, leading to the same line being planted by many farmers.
To me, all of this emphasizes the need for maintenance of landraces as a germplasm source, but does not say that we should choose “old-fashioned” landraces over selected varieties. It also tells me that we should probably have more breeders producing more lines from more diverse germplasm. There are more small breeders out there than many people think, but their reach is necessarily smaller than the giant seed companies.
What I’d like to know is where the writer got the impression that “reinstituting” landraces is being seriously considered as a climate change adaptation strategy. Can anyone point me to a source for this idea?
Where did you get the impression that the author has that impression? He claims that “old-fashioned seeds are better at dealing with variable weather”. It is my impression that he wanted to avoid that his readers draw the conclusion that these seeds should therefore be reinstituted; which would seem logical. And so he brings it up to dismiss it, as “their use will mean less food”.
I just wonder why the writer used the word “will” (rather than, for example, “would”) in the paragraph I quoted.
“Reinstituting their use will mean less food.”
You are right.
Or maybe I’m over-reading a short sentence in a short paragraph in a long article.
I doubt it. This short sentence seems to be the prevailing view among people who don’t know anything about plant breeding.
How much does The Economist know about agriculture?
Searching here revealed that only one journalist lists it as her theme area.
I’m worried.
You guys! Get real. Journalists don’t have to know much about a subject, they have to know how to find out. A short sentence in a long article and you’re all of a twitter.
There was a similar short couple of sentences in another long article, a while back, about the banana diseases sweeping Africa, and nobody here or elsewhere raised a peep.
If you want something to worry about, Jacob, worry about the lack of understanding of agriculture among environmentalists, especially “conservationists”, and climate-change wallahs.