Category: Genetic diversity

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Grape genomes galore

A little over six months ago researchers reported a high quality DNA sequence for the Pinot-Noir grape. ((Not, you will note, Merlot, which would have been way too easy.)) Now comes news that the USDA is planning to do a genetic analysis of more than 2000 additional grape varieties in its collection. These will not be full sequences. Rather, researchers will be looking for SNPs, ((Single Nucleotide Polymorphisms, pronounced “snips”.)) places where the DNA sequence differs by just one letter between two individuals. These SNPs are most useful as markers that can be used to identify areas of the DNA that may harbour important traits. Breeders and researchers can use them to track the inheritance of specific traits; USDA singles out disease resistance and berry colour. And that will speed up the breeding of new grape varieties.

I know hardly anything about the world of grape breeding, but someone out there may be able to tell me: when was the most recent introduction of a newly bred variety that gained any traction within the world of wine-making? ((I’m told this type of question is called a bleg; using a blog to beg for an answer (not money).))

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Plants and health

Yes, yet another thematic trifecta. I swear I don’t go out looking for these, they just pop up every once in a while. CABI’s excellent blog had a piece today about CABI’s own fungal genetic resources collection and its value as a source of useful compounds. It includes Fleming’s original penicillin-producing strain so it does have form in that regard. Then Seeds Aside has a post on variation among olive varieties in a gene for an allergenic protein found on the pollen grain. And finally, over at the Oxford Dictionary of National Biography, a thumbnail sketch of the redoubtable Phebe Lankester, who wrote extensively on both botany and health — and occasionally on the link between the two — in the latter part of the 19th century. ((Ann B. Shteir. (2004) “Lankester, Phebe (1825–1900).” Oxford Dictionary of National Biography, Oxford University Press. [http://www.oxforddnb.com/view/article/58526, accessed 10 April 2008].))

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Meta-analyzing diversity

If you’ve just arrived from Tangled Bank, welcome. And be aware that there’s a follow-up post.

A couple of meta-analyses on the menu today.

ResearchBlogging.org Devra Jarvis and Bioversity International colleagues, together with numerous co-authors from national programmes around the world, have a paper in PNAS summarizing the results of a 10-year effort to establish the scientific bases of on-farm conservation of agrobiodiversity. ((Jarvis, D.I., Brown, A.H., Cuong, P.H., Collado-Panduro, L., Latournerie-Moreno, L., Gyawali, S., Tanto, T., Sawadogo, M., Mar, I., Sadiki, M., Hue, N.T., Arias-Reyes, L., Balma, D., Bajracharya, J., Castillo, F., Rijal, D., Belqadi, L., Rana, R., Saidi, S., Ouedraogo, J., Zangre, R., Rhrib, K., Chavez, J.L., Schoen, D., Sthapit, B., Santis, P.D., Fadda, C., Hodgkin, T. (2008). A global perspective of the richness and evenness of traditional crop-variety diversity maintained by farming communities. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0800607105))

Varietal diversity ((The unit of analysis was the farmer-recognized and named variety.)) data on 27 crops grown on 64,000 ha by 2,041 households in 26 communities in 8 countries on 5 continents were pulled together in a stunning feat of synthesis. Are any generalizations possible from such a massive dataset? Well, perhaps surprisingly, yes. Let me pick out the highlights:

  1. Households growing traditional varieties generally grow more than one (1.38-4.25).
  2. Households within a community tend to grow somewhat different sets of traditional varieties.
  3. Larger fields generally have more traditional varieties, but smaller fields tend to be more different in varietal composition.

There’s much more to this rich analysis than that, but the take-home message can be pretty easily stated: crop genetic diversity can still be found on-farm because even neighbouring families choose to grow different traditional varieties, and generally more than one. Especially families tending smaller fields, who will presumably be poorer and living in more marginal conditions. The conoscenti will recognize a familiar meta-narrative, but it is good to have solid data from a wide range of crops and from all over the world.

The next paper I want to talk about looked at genetic diversity in wild clonal species as it relates to their breeding system. ((Honnay, O., Jacquemyn, H. (2008). A meta-analysis of the relation between mating system, growth form and genotypic diversity in clonal plant species. Evolutionary Ecology, 22(3), 299-312. DOI: 10.1007/s10682-007-9202-8))

Summarizing 72 genetic diversity studies, including of a couple of crop relatives, the authors found that populations of self-incompatible clonal species tended to have fewer genotypes, more unequally distributed (i.e., with a few dominant clones), than populations of self-compatible clonal species. It would be interesting to see if this relationship is also present in vegetatively propagated crops. I don’t think the previous dataset would help with that, however. Only two clonal crops were included in the on-farm analysis, cassava and taro. Interestingly, they had the highest average levels of community-level varietal richness (33) compared to seed-propagated species.