Category: DNA

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Chinese interdependence

ResearchBlogging.orgA paper just out in Agricultural Science in China reminded me that I wanted to say something about one of the great meta-narratives of plant genetic resources: interdependence — the old no-country-is-self-sufficient-in-PGR mantra. Which, unlike some other meta-narratives, is generally recognized as being true — witness the International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA). And that despite the fact that measuring interdependence is not by any means easy, and has not often been done.

The paper which caught my eye is not really primarily about interdependence. ((ZHAO, Y., Ofori, A., & LU, C. (2009). Genetic diversity of European and Chinese oilseed Brassica rapa cultivars from different breeding periods. Agricultural Sciences in China 8(8):931-938. DOI: 10.1016/S1671-2927(08)60297-7.)) It just shows that cultivars of winter oilseed rape (canola) from China are very distinct from European ones, on the basis of molecular markers. Which presumably means that yield gains could be had from cross-breeding between the two groups. Which does say something about interdependence, but not very forcefully.

However, that paper reminded me about two others that a colleague had recently sent me, along with the thought that they should be enough, in a perfect world, for China to ratify the ITPGRFA.

The first is about soybean. ((Qin, J., Chen, W., Guan, R., Jiang, C., Li, Y., Fu, Y., Liu, Z., Zhang, M., Chang, R., & Qiu, L. (2006). Genetic contribution of foreign germplasm to elite Chinese soybean (Glycine max) cultivars revealed by SSR markers. Chinese Science Bulletin, 51(9):1078-1084. DOI: 10.1007/s11434-006-1078-4)) It shows, using molecular markers again, that a couple of elite Chinese cultivars benefited greatly, in terms of both specific traits but also their difference from previous Chinese cultivars (that is, the genetic base of the crop as a whole was broadened) from the fact that US and Japanese germplasm was involved in their development, rather than just Chinese stuff.

The second paper makes the interdependence point even more strongly by quantifying the contribution of foreign maize germplasm to production in China, rather than just genetic diversity. ((LI, H., HU, R., & ZHANG, S. (2006). The Impact of US and CGIAR Germplasm on Maize Production in China. Agricultural Sciences in China, 5(8):563-571. DOI: 10.1016/S1671-2927(06)60093-X.)) It turns out that a 1% contribution by US material (based on the coefficient of parentage) translates to an additional 0.01 t/ha (0.2%), and a 1% contribution by CIMMYT germplasm to an additional 0.025 t/ha.

The conclusion: “The extensive utilization of US and CG germplasm improved maize yield potential in China… The government should provide funds to support research on germplasm introduction…” And, we could add, it should ratify the ITPGRFA. No country is self-sufficient in PGRFA. Not even the largest.

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Dog fight over canine origins

We’ve pointed briefly to recent studies on the origins of the domestic dog, where two schools of thought hold sway. The conventional version offers east Asia — China, more or less — as the centre of dog diversity and, by implication, the place where dogs were first domesticated. An apostate view is that dogs were domesticated in Africa and perhaps in Europe too.

There’s no clear resolution in sight yet, but it looks as if the Chinese dog may be on top. A news report in Science gives details of (and links to) a new and more detailed study from Peter Savolainen and his team:

The data reaffirm a single site for domestication and pinpoint the origin of the domesticated dog to a region south of the Yangtze River, where wolf taming was quite common, Savolainen’s team reports today in Molecular Biology and Evolution. That’s where the largest number of similar groupings of DNA, called haplogroups, is found. As the researchers looked at dogs farther from this region, they saw fewer haplogroups; Europe had only four, for example. “The gene pool we are finding in Europe and Africa are a subset of the South Chinese gene pool,” says Savolainen.

But the African dogs aren’t rolling over yet.

Carles Vilà of the Biology Station of Doñana-CSIC in Seville, Spain … points out that other genetic studies suggest dogs date back at least 20,000 years and that archaeological remains of dogs in Europe are almost as old. … “I’m not convinced by the results,” he says, “and I do not think this is the last that we will hear about the time and place of the domestication of dogs.”

That seems certain. Back in the days before DNA a multiple-origins theory was all the rage, but then, it was for H. sapiens too.

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Nibbles: European agricultural origins, Drought, Native American ranching, Sorghum, Anthocyanins in apples, Dog coat, Pear cider

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Upstream blast

ResearchBlogging.org Blast is one of the worst rice diseases. I believe that, thanks to the breeders, most modern varieties have decent levels of resistance. After all, they can be used in varietal mixtures to protect traditional glutinous rice varieties from blast. ((Zhu, Y., Chen, H., Fan, J., Wang, Y., Li, Y., Chen, J., Fan, J., Yang, S., Hu, L., Leung, H., Mew, T., Teng, P., Wang, Z., & Mundt, C. (2000). Genetic diversity and disease control in rice. Nature, 406 (6797), 718-722 DOI: 10.1038/35021046 Also see this post.)) Unfortunately, much of this resistance is not durable, because the pathogen overcomes it with time.

For a long time, durable resistance has been known to exist in some Japanese varieties. But these varieties have not been useful for resistance breeding, as the resistant parent also brought along undesired characteristics: the offspring always had poor eating quality.

Shuichi Fukuoka and colleagues have found out why. They report in Science ((Fukuoka, S., Saka, N., Koga, H., Ono, K., Shimizu, T., Ebana, K., Hayashi, N., Takahashi, A., Hirochika, H., Okuno, K., & Yano, M. (2009). Loss of Function of a Proline-Containing Protein Confers Durable Disease Resistance in Rice Science, 325 (5943), 998-1001 DOI: 10.1126/science.1175550
see also Normile, D. (2009). New Strategy Promises Lasting Resistance to a Rice Plague Science, 325 (5943), 925-925 DOI: 10.1126/science.325_925)) that it is because of a tight genetic linkage. Resistance is conferred by the Pi21 locus, and:

The eating quality of plants carrying the elite cultivar’s chromosomal sequence from a point less than 2.4 kb downstream of the Pi21 locus was equivalent to that of the elite cultivar, and the plants showed a high level of blast resistance. In contrast, plants carrying the donor chromosomal sequence up to 37 kb downstream of the Pi21 locus showed inferior eating quality.

By crossing in just the right bit of the chromosome, and making sure that the neighboring areas do not tag along, resistance can now be transferred, without spoiling the taste.