Author: Jeremy Cherfas

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Shades of blue, Tokyo style

The Human Flower Project reports on a DIY indigo-dyeing shop in the heart of Tokyo. A fine idea, for all sorts of reasons. It puts people in touch with a natural, plant-based dye and offers us a chance to talk about agricultural biodiversity and even plant biochemistry.

The Human Flower Project’s page shows a photograph of the source of indigo labelled Polygonum tinctorium, also known as Chinese indigo. I fondly remember visiting an indigo demonstration dyer near Toulouse, in France, that sourced the dye from woad, Isatis tinctoria. And then there’s the Asian (or true, sic) indigo, Indigofera tinctoria. Native American tribes apparently used other legumes closely related to true indigo for their blue dyes.

What they all have in common is the process to get the colour. Young leaves are mashed with water and then encouraged to ferment. That results in a greenish sludge. The fabric is immersed in the sludge and then hung up to dry. As the pigments oxidize, they turn blue, and expert dyers can control the shade of blue by adjusting the duration of the oxidizing step, and other factors. (Loads more information here.)

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It struck me that indigo would make a marvellous central topic for one of those the-entire-history-of-the-universe-as-seen-through-a-single-neglected-thing books. There’s revolt and revolution, trade wars, the origins of modern organic chemistry, mercantile colonialism, slavery and rice, and pretty colours. Kew contibuted its model of an indigo factory to the BBC’s history of the world in 100 objects, but the model does not seem to have been the subject of one of those wonderful broadcasts. A pal of mine did a book on madder, another brilliant dye; I couldn’t find anything similar for indigo (although there is plenty of woo). Publishers! I am available.

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The agrobiodiversity of Wayanad District in Kerala

An extremely long explanation of the wonderful “‘home garden’ system” 1 of Wayanad District in the south Indian state of Kerala, from the Satoyama savants at UN University. There’s a video, natch, which is very pretty and very informative. One scene of four women pounding what looks like millet looks lovely, dangerous, and unnecessary. Couldn’t they get a mini-mill?

What I don’t get is why the headline says “South Indian agricultural model mimics fragile ecosystem”. Looks to me like the agricultural model is a lot more robust and resilient than the ecosystem. But what do I know?

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Zombi bean resurrected?

Vigna vexillata is a close relative of the cowpea (V. unguiculata) that (sometimes) rejoices in the common name Zombi Bean. (It is also called the tuber cowpea.) It’s hard to tell whether this is a “famine food” harvested from the wild, a plant being domesticated and on its way to becoming a crop, or a full-fledged crop species. Either way, scientists in Australia have been doing their darndest to understand how it can best be improved. The result, so far, is three back-to-back papers in Crop & Pasture Science.

  • Genotypic variation in domesticated and wild accessions of the tropical tuberous legume Vigna vexillata (L.) A. Rich. doi:10.1071/CP10029
  • Genetic compatibility among domesticated and wild accessions of the tropical tuberous legume Vigna vexillata (L.) A. Rich. doi:10.1071/CP10060
  • Expression of qualitative and quantitative traits in hybrids between domesticated and wild accessions of the tropical tuberous legume Vigna vexillata (L.) A. Rich. doi:10.1071/CP10084

But not, yet, any improved varieties.

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Mashing up banana wild relatives

Over at the Vaviblog is a detailed discussion (though not nearly as detailed as the paper) of a new paper outlining a new theory for the origin of the cultivated banana. 2

Edible bananas have very few seeds. Wild bananas are packed with seeds; there’s almost nothing there to eat. So how did edible bananas come to be cultivated? The standard story is that some smart proto-farmer saw a spontaneous mutation and then propagated it vegetatively. Once the plant was growing, additional mutants would also be seen and conserved. In fact this “single-step domestication” is considered the standard story for many vegetatively-propagated plants, such as potato, cassava, sweet potato, taro and yam. And while it may be true for those other crops, evidence is accumulating that it may not be the whole story for bananas.

Leaving the details aside, De Langhe and his colleagues propose that instead of a single step, at least two were involved, with a proto-cultivated banana back-crossing with one of its wild relatives and then being seen by the proto-farmer as an improvement to be added to her proto-portfolio of agricultural biodiversity. Something very like that is going on today among cassava farmers, for example; they allow volunteer seedlings, the product of sexual reproduction between already favoured clones and wild relatives, to flourish in their fields and then select among them. 3 Banana farmers could easily have done the same.

To quote again from The Vaviblog:

The big question, of course, is “what does any of this matter?”. And the surprise is that it really does. Banana breeding is difficult at the best of times; no seeds, no pollen, you can imagine. But if the backcross hypothesis is true, then the current approach to banana breeding, which De Langhe et al. describe as “substituting an A genome allele by an alternative derived from a AA diploid source of resistance or tolerance to biotic and abiotic stress”, might be misguided. If the chromosomes are not “pure” A or B, and if backcrosses were involved in the origin of banana varieties, maybe breeders should look again at some of the diploid offspring from their crosses and see whether they could be further backcrossed to come up with types that are more use to farmers.

Now, what I really need is for one of the handful of people who really understand this stuff to tell me where I’ve misunderstood it.

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Orange sweet potato not a “magic bullet”

They are no magic bullet, but next to a more diverse diet, they may prove to be the most cost-effective approach to reducing hidden hunger.

This statement may well be something of a breakthrough, which is why I think it deserves some prominence here. In the battle against malnutrition there has long been a general needless opposition among supplements, biofortification (by genetic engineering and conventional breeding) and dietary diversity. Each has its place, and if we are highly biased towards dietary diversity, it is because we think it is the most sustainable option, with plenty of spin-off benefits. To hear IFPRI and HarvestPlus suggest that orange-fleshed sweet potatoes may actually be less cost effective than dietary diversity in fighting malnutrition is music indeed.