Wild cassava genetics used to document past changes in vegetation

ResearchBlogging.orgWas southern French Guiana always forested, a refugium for forest species, or was it dominated by more open vegetation during drier, glacial times? A recent paper in Molecular Ecology tries to decide between these competing hypothesis, and the interesting thing for us at the Agricultural Biodiversity Weblog is that it does so through a genetic study of a crop wild relative. ((DUPUTIÉ, A., DELÊTRE, M., DE GRANVILLE, J., & MCKEY, D. (2009). Population genetics of Manihot esculenta ssp. flabellifolia gives insight into past distribution of xeric vegetation in a postulated forest refugium area in northern Amazonia. Molecular Ecology, 18 (13), 2897-2907. DOI: 10.1111/j.1365-294X.2009.04231.x.))

Manihot esculenta ssp. flabellifolia is the closest wild relative of cassava. It is “distributed on an arc partly encircling the Amazon basin, from eastern Bolivia and Peru eastward to northeastern Brazil, northward to the Guianas and then westward to Venezuela.” Its habitat is the transition zone between forest and cerrado in the south, and open environments such as savannas and rocky outcrops in the north. In French Guiana, which was the focus of the study, it is found both in the coastal strip, and on isolated granitic outcrops (inselbergs) in the forested south, with a large gap in between.

Seven microsatellite loci were used to investigate the genetic relationships among 14 populations, 4 from inselbergs and the rest from the coast. The results are pretty easily summarized. First, the inselberg populations were very similar to each other. Second, they were quite different as a group from the coastal populations. Finally, the coastal populations were highly differentiated among themselves.

So, what do these results tell us about the past vegetation history of the region? One conclusion was that the coastal populations (which incidentally, in contrast to the inselberg populations, showed some evidence of introgression from the crop) are relatively recent, and arrived from savannas to the west through a series of bottlenecks, rather than from the south. As for the southern inselberg populations, given the limited range of pollen and seed flow, they seem to be the remnants of a formerly more extensive, fairly homogeneous population. ((Conservation question: Does that mean that seed of the 4 inselberg populations could be bulked and kept as a single accession? Answers on a postcard, please.)) That suggests that southern French Guiana was drier and had a more open vegetation before the Late Glacial Maximum 10,000 years ago. There was probably a forest refugium in the central part of the country, but not in the south.

Assuming, of course, that the adaptation of the species hasn’t changed much along the way. It remains to be seen whether the same pattern will be found in other taxa. Perhaps other species of agrobiodiversity interest will be investigated in the same way.

Anthropologists and geneticists see the origin of agriculture in different ways

Dorian Fuller has answered Paul Gepts’ comment on Dorian’s post at The Archaeobotanist on the multiple origin of agriculture, which I originally blogged about a few days ago. Let’s remind ourselves of the argument.

This was Dorian’s parting statement on the original post:

…agriculture, like modern human behaviour, was not a one time great invention, but the product of social and environmental circumstances to which human groups with the same cognitive potential responded in parallel ways.

Paul Gepts countered with this:

As a geneticist, I am somewhat surprised that the issue of parallel inventions of agriculture is still an issue… biochemical and molecular data also show distinct, and likely, independent domestication in different geographical areas, not among only among different crops, but also within a crop gene pool.

And now Dorian again:

My sense is that most of the genetics community has shifted towards seeing multiple areas of independent origin, but within archaeology there is still a penchant for reducing historical complexities to as few origins as possible — often focusing on where more archaeological research has taken place rather than considering other forms of evidence (biogeography, genetics) that should encourage us to take up research in the less-explored or unexplored areas.

Read the full exchange.

Nibbles: Drought resistant rice, Bees, Bison, Coffee in Kenya, Cassava in Africa, Pigeon pea, Chickens in Uganda, Green ranching in the Amazon, Climate change, Dates, Museums and DNA, Organic, Ecology meet

Protecting rice in Thailand and India

I’ve pointed to a couple of different stories in the past few weeks dealing with the legal protection of rice diversity, and I thought it might be a good idea to bring them together here.

The first concerned aromatic Jasmine rice from Thailand. This was the lead paragraph:

On Wednesday, His Majesty the King applauded Thai scientists and those involved in the patenting of genes that can control the aroma of Thai jasmine rice. His Majesty said the patent would ensure that Thais take pride in eating Thai rice. They won’t have to eat rice that has a foreign patent.

However, it turns out the patent is actually for a transgenic aromatic rice, which is not quite the same thing. In fact, it would be difficult to protect the gene controlling the aroma of Thai rice, because that same gene also controls aroma in all other aromatic rices around the world. A recent paper suggests as much:

The badh2 mutation … [was] surveyed in a representative rice collection, including traditional aromatic and non-aromatic rice varieties, and strongly suggested a monophylogenetic origin of this badh2 mutation in Asian cultivated rices.

The second article is about rice with a red pericarp. This is often said to have health benefits, due to the accumulation of various nutrients along with anthocyanins.

Scientists are trying to protect a traditional rice variety that is on the verge of extinction in Himachal Pradesh. The red rice is more disease-resistant and hardier than strains cultivated commercially over most of India and can lend that through cross-breeding.”We are trying to provide legal protection to the vanishing red rice variety, grown in the state for centuries, by bringing it under the ambit of the Protection of Plant Varieties and Farmers’ Rights Act 2001,” R.P. Kaushik, director of the rice research centre at CSK HP Krishi Vishvavidyalaya, an agricultural university based in Palampur. told IANS.

Now, red pericarp is the ancestral state in rice, and it’s occurrence is geographically widespread. ((It turns up in at least 20 countries in Asia and Africa, according to our mole at IRRI.)) So, again, if this rice is to be protected, it could not be protected simply as “red rice”, but rather as a particular, clearly defined, variety of red rice. Anyway, as Bhuwon points out in his comment on the article, if it fetches such high prices as the article suggest, is there really a need for legislative protection?

But then, arguments for legal protection of genetic resources are not always grounded in anything more than a sort of reflexive place-ism.