Category: In situ

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Restoration is germplasm use too

ResearchBlogging.orgIt is well known that plant populations do best when they grow close to where they originally came from. A myriad reciprocal transplant experiments going back decades attests to the power of local adaptation. But how close is close? The question is of very real practical importance if you’re trying to restore a habitat. By definition, the local population is gone. What is the maximum distance you should be willing to go to collect material to re-establish it?

Three hundred kilometers is the answer given in a paper just out in Ecological Applications. ((Travis, S., & Grace, J. (2010). Predicting performance for ecological restoration: a case study using Spartina alterniflora Ecological Applications, 20 (1), 192-204 DOI: 10.1890/08-1443.1)) There’s also a discussion over at Conservation Maven. The authors worked on the salt marsh grass Spartina alterniflora, which is commonly used in ecological restoration of wetlands in North America. They collected germplasm at 23 sites from Texas to Maine, genotyped them using neutral markers, and then grew them all in a “common garden” experiment in Louisiana, where they measured in various ways how well each population did. The control was a population just across a canal from the experimental site.

It turned out that clone diameter, number of stems and number of inflorescences at the experimental site, as well as genetic distance, were all significantly affected by measures of the geographic distance between the source and the experimental site. For populations up to about 300km away along the coast, performance in the common garden was similar to the control. Go further, and the source populations do not do as well where they are planted.

The authors make quite specific recommendations for restoration. Use material from at least three populations within 300km of the restoration site, and 100km if you want material that is not only maximally locally adapted but also not significantly genetically different from the original population at the restoration site.

Now, I don’t know how widely applicable these recommendations might be. I don’t know the restoration literature at all. A cursory look revealed a fairly well-developed theoretical framework, the “restoration gene pool concept.” Which has been used to develop a decision support tool.

As I say, I don’t know much about restoration. So I don’t know to what extent this sort of thing has been applied to crop wild relatives. To me, “use” of crop wild relative germplasm means use in breeding. But that is clearly very narrow thinking, and I should be ashamed of myself.

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Nibbles: Truffles, Botanicals, Cell phones, Child nutrition, Chocolate, Georgia

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Tributes to Bob Rhoades

Ashamed of the brevity of our note on the passing of Prof. Robert Rhoades a few days back, I welcome this opportunity of giving more prominence to comments on that post from a couple of friends of his.

From Cary:

Bob Rhoades was a wonderful man who made a tremendous contribution to our field. He was indeed a great teacher, advisor and researcher. In addition to what is mentioned in the short article above, let me note that he worked for a number of years at CIP, and was the author of another memorable National Geographic article, “The Incredible Potato.” He also co-founded the Southern Seed Legacy with his wife, Prof. Virginia Nazarea, who is also a very prominent figure in crop diversity. Personally, I treasure the times I spent with Bob at his farm outside Athens, and a trip we made on the back-roads through Georgia, South Carolina and North Carolina, visiting seed savers and conservationist along the way.

And from Pablo:

I am so saddened to hear that Bob Roades died. He was perhaps the first social scientist to systematically document, improve and extend farmer’s knowledge about agricultural biodiversity. His modest and warm approach in the field, his gentle humour, and sharp intellect earned him the respect of farmers everywhere he worked. As anthropologists we are proud of the pathbreaking work that Bob did, charting the way so that many others could also contribute. Bob loved speaking about his farm in Georgia, his Oklahoma roots, his marriage to Virginia. His generosity and ideas keep him dear to me. My condolences to Virginia and his family.

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More on future-proofing germplasm collections

A reply to Walck & Dixon from Brian Forde-Lloyd, Nigel Maxted and Luigi Guarino.

ResearchBlogging.orgIn Walck and Dixon’s opinion (Nature 462: 721, 2009) it’s ‘time to future-proof plants in storage’, but how novel and useful is this idea? ((Walck, J., & Dixon, K. (2009). Time to future-proof plants in storage Nature, 462 (7274), 721-721 DOI: 10.1038/462721a)) Few would argue with the principle that we need to maximise the range of genetic diversity conserved ex situ, but some of the issues raised need further consideration.

1. Collecting species at the limits of their ranges could be a good idea — this could be where adaptations most likely to be occurring; for wild wheat populations, genes thought to be adaptive to biotic and abiotic stress have been found to be highly variable in some ecological circumstances (e.g. wild wheat in Israel). But, more generally, population genetic theory suggests that genetic diversity will reduced at range margins, where population sizes will be small.

2. Collecting samples every 10 to 20 years may not be long enough for genetic adaptation to be manifested, particularly in perennial species, but equally may not be frequent enough to prevent severe genetic erosion under rapid climate change of annual species.

3. ‘Conditioning’ seeds at high temperature to allow for the selection of genotypes with temperature tolerance will have a seriously adverse effect on genetic diversity as a whole. Regenerating seeds from small numbers followed by their reintroduction will impose a severe genetic bottleneck. On the positive side, evaluating germplasm for adaptation to abiotic stress has certainly been encouraged for many years now by those scientists, genetic conservationists and plant breeders who continue to value and conserve those wild plant species that are relatives of crops.

4. Mixing seed samples to allow ‘cross-breeding’ and then allowing selection to act upon the genetic variation that results is not dissimilar to plant breeding. But is it not just as likely that outbreeding depression rather than the desired heterosis will result? There is a growing opinion amongst plant breeders anyway that conventional plant breeding is too slow a process to keep up with climate change. Also, is it feasible to consider ‘breeding’ is manner suggested all wild species before they are reintroduced to the wild.

5. ‘Conditioning’ and mixing seed sample then replanting them in the wild is likely to result in genetic pollution and potential diluting of local ecotypic adaptation. This has already been shown to occur in species with wild and cultivated components. The niche that any plant grows within is defined by a complex range of biotic and abiotic interactions and not all will be impacted by a changing climate.

6. But here’s the real conundrum, if seed banking (ex situ conservation) is currently inadequate, why not simply rely upon in situ conservation of wild plant species in genetic reserves? It would seem that the arguments that climate change will preclude such an approach in the near future applies equally to the suggestions made in this article.

In the final scheme of things, complementary approaches to the conservation of plant diversity, both ex situ and in situ, are important for that diversity to be used to its fullest, and not just for reintroduction alone. This needs strengthened support in the face of climate change, the scientific case for which has been argued for at least the last 20 years.