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When the levee breaks

A piece in The Tribune, an English-language daily out of Punjab, reminded me that we have discussed crop diversity and flooding quite a bit here over the years. The article, entitled “Community seed banks help flood-hit Punjab farmers restore crop productivity,” discusses how an initiative of Punjab Agricultural University helped farmers establish community-level repositories of crop diversity that are coming in useful in recovering from recent flood.

Sharing his experience, Paramjeet Singh, a farmer from Baopur Jadid, said that timely access to quality seeds through the community seed bank enabled him to sow his crop without delay and achieve a yield of around 23 quintals per acre.

Farmers acknowledged that the initiative has significantly reduced reliance on outside seed sources, minimised sowing delays, and improved overall crop outcomes. They are also retaining seed of the new wheat variety PBW 872 for the next season. The initiative has strengthened local seed exchange systems and enhanced community preparedness against climate-related challenges. By ensuring the availability of quality seeds within villages, the Community Seed Bank initiative is contributing to sustainable agricultural development and improving the livelihood security of farmers in flood-affected areas.

A couple of points about this are worth noting.

First, only improved varieties are mentioned in the article, but normally community seed banks will also conserve local landraces. I don’t know if this is the case in Punjab, but I do hope so. As Jeremy put it here all of 15 years ago, in a post on a study of rebuilding cowpea cultivation after flooding in Mozambique, that and similar experiences support “the more general conclusion that seeds already in the local system offer the best chance of restoration.” Although do read the comments to that post. It seems that in another case some farmers weren’t particularly interested in recovering the exact varieties they had lost.

Which brings me to the second point. And that is that I also hope that those community seed banks have good links with the national genebank. This can act both as back-up and as a source of new diversity, as I suggested myself in a more recent post after floods in Pakistan.

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Underselling breeding, and conservation

Crops with massive … importance, clear biological upside, and real demand for better genetics — but a system where breeding remains small, underfunded, and structurally difficult to scale.

What crops, you ask? “Opportunity crops,” perhaps? Fonio, say, Bambara groundnut, or any nnumber of African leafy vegetables. Those would have been good guesses, but actually I cheated, so no. The word hidden by the ellipsis is actually “economic,” and the quote comes from a Reddit post on coffee breeding. 1

That of course makes the observation even more amazing. As the Reddit poster goes on to point out:

We’ve built a ~$100B global industry that depends on plant genetics… while seemingly allocating only a negligible fraction of that value to actually improving those genetics.

And, I would add, allocating an even more negligible fraction to conserving those genetics (despite the fact that there’s a pretty solid strategy for how to do that). Which goes for opportunity crops too.

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Rare today, relevant tomorrow: new lessons from a really old barley experiment

I was vaguely aware of the Composite Cross II (CCII) long-term experiment with barley, not least because of a Brainfood entry a couple of years ago. But I didn’t know a whole lot about it, so when a link to a recent thesis by Jill Marzolino at UC Riverside referencing it popped up in my feeds, I decided to look into it a bit more.

Harry Harlan and Mary Martini set up the experiment way back in 1929, in an effort to come up with barley varieties better adapted to the Californian environment. They started out with 28 diverse barley varieties from all over the world, made all possible crosses among them (though in only one direction), bulked together all the seeds they got, and planted a random sample of the mixture at Davis, California. The next year, they harvested the resulting crop, and sowed a sample of the seeds they obtained again in the same place.

And so on, for decades. Researchers following in the footsteps of Harlan and Martini planted 5,000-20,000 seeds year after year and left them to it, for 58 generations, saving a sample of the harvest along the way. This is called a composite cross population, or sometimes a composite hybrid mixture. When used in crop improvement, the process is sometimes referred to as evolutionary plant breeding, and has been proposed as a useful strategy for adapting crops to climate change.

Anyway, in the days of DNA sequencing, you can also see how CCII is an incredible resource for just trying to figure out how — and how fast — evolution works.

The paper I referenced in Brainfood in 2024 did just that. In Natural selection drives emergent genetic homogeneity in a century-scale experiment with barley, the authors showed that natural selection pretty quickly and drastically narrowed the genetic diversity of the original diverse population, affecting especially genes regulating the timing of flowering and reproduction. That basically allowed the plants to avoid drought. Yield also doubled, though that was less than plant breeders were able to achieve over the same period.

The thesis that caught my eye today is entitled Uncovering the Genetic Basis of Local Adaptation With Long-Term Evolution Experiments in Barley, and comes from the same lab. Dr Marzolino also looked at flowering time, but the chapter that really struck me was the one on “genetic rescue.” She found that when she planted the CCII at a different site, in Bozeman, some genetic variants that had been incredibly rare at Davis suddenly exploded in frequency. In her words:

This result indicates that very rare maladapted types persist in the CCII. It is not clear how they are maintained, but perhaps fluctuating environmental conditions from year to year alter the fitness of these types enough for them to persist… It remains unclear how long these rare types can be maintained in a population. Maintenance of rare types could be critical for the longer term survival of many plant species in a changing world.

Something for genebank managers to ponder. The normal practice is to regenerate genebank accessions under environmental conditions which are as close to ideal for the particular germplasm in question as possible, in order to ensure a good harvest of high quality seeds. But this result suggests it might actually be worth considering occasionally subjecting sub-samples to a few regeneration cycles in a contrasting environment. Might that not rescue some interesting — not to mention useful — genes?

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Brainfood: Clonal crops edition