Agriculture between High Tech and Organics

Transcription

1 Agriculture between High Tech and Organics Denver AAAS 2003 Symposium February 15 Klaus Ammann

2 Natural geneflow with its many possibilities

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4 Evolutionary character of gene flow 1. recombination 4. non-random mating 2. mutation 5. natural selection 3. genetic drift 6. gene flow Mutation is the ultimate source of new genetic varieties in a species. However, gene flow can be responsible for the introduction of new alleles into a population of a species. Generally the most rapid and dramatic evolution is due to natural selection.

5 Modelling gene flow

6 The statistic,, reflects the proportion of the observed genetic variation that can be explained by partitioning between populations (values range from 0 to 1.0). is calculated by: where is the variance of the frequency of allele p, p is the mean allele frequency across all samples, and n is the number of alleles [ Wright, 1969]. Using this value, the number of individuals exchanged between two populations per generation may be estimated by: where N is the number of individuals in a given population and m is the proportion of those individuals resulting from immigration [ Wright, 1969]. As a benchmark, values of Nm > 1 (corresponding to ) are typical of ``high gene flow'' species, which will become genetically homogeneous in the absence of counteracting forces

7 Counteracting forces, especially differential selection, may be very strong and may maintain population differentiation in the presence of gene flow far in excess of Nm = 1. Some attributes of marine zooplankton suggest that population differentiation may be possible despite expected high gene flow with ocean mixing. In particular, the very high mortality rates (>>99 %) that are characteristic of marine zooplankton may allow strong selection to maintain genetic differences among populations. U.S. National Report to IUGG, Rev. Geophys. Vol. 33 Suppl., 1995 American Geophysical Union

8 Gene Flow: The reality since centuries in Mexican Maize and Teosynte

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11 The results imply that, since the domestication of maize, teosinte and maize have remained relatively isolated in genetic terms (Doebley 1984; López and Kato 1990), suggesting that they have had the opportunity to evolve independently. Nevertheless, the possibility of a low frequency of introgression is not completely discarded, given that maize and teosinte coexist sympatrically and form fertile hybrids in many regions.

12 The still unfinished agenda in maize evolution and breeding studies

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18 A Proposal on How to tackle with Gene Flow in Modern Agriculture: The Dutch Swiss Coding System a precautionary approach to study gene flow

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20 Gene Flow in Switzerland between crops and their wild relatives in Switzerland Df: Frequency Dd: Dispersal rate Dp: Hybridization

21 Potential Risk of Gene Flow to wild relatives for 19 Swiss crops: Freq uenc seed Hy bridization, p ollen transp ort etc. dispersal tom ato 2 tobacco beet endive 3 4 turnip 5 lettuce cabbage 3 radish 4 5 rape 4 0 maize 1 barley 2 wheat carrot 3 rye chicory potato 2 3 clovers 4 alfalfa 5 grasses

22 Do viable fertile hybrids form between the crop and wild/weedy relatives? Does the crop reproduce sexually? Yes or insufficient information Does the crop have outbreeding potential with relatives in Switzerland? Yes or insufficient information No Do the crop-relative breeding systems permit gene flow in and out? Yes or insufficient information No Does the flowering period of the crop and weed/weedy relatives overlap, or nearly so? Yes or insufficient information No Do crop and wild/weedy relatives share the same means of pollination? Yes or insufficient information No Do crop and wild/weedy relatives naturally crosspollinate, fertilize, and set viable, fertile seeds under field condition? yes or insufficient information No Go to the ecological performance of transgenic wild/weedy plants. (in case of an insufficient safety distance policy and in absence of biological containment policy stop development with risky transgenes LOWER RISK Go to scheme 2 LOWER RISK Go to scheme 2 LOWER RISK Go to scheme 2 LOWER RISK Go to scheme 2 LOWER RISK Go to scheme 2 No LOWER RISK Go to scheme 2 Scheme 1

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24 Published online before print September 14, 2001 Proc. Natl. Acad. Sci. USA, /pnas Corn pollen deposition on milkweeds in and near cornfields John M. Pleasants*, Richard L. Hellmich, Galen P. Dively, Mark K. Sears, Diane E. Stanley-Horn, Heather R. Mattila, John E. Fosteri, Thomas L. Clarki, and Gretchen D. Jones**

25 Gene stacking in volunteers is inevitable but the SCIMAC guidelines of a separation distance of 50m between HT cultivars that are not varietal associations and perhaps not HT partially restored hybrids will reduce its occurrence. Increasing separation distances between non-hybrid crops will only have a small impact on its occurrence unless the isolation distances are increased to 400m or more.

26 Crawley et al. 2001, Nature Vol. 409, 9 February Figure 1 The performance of conventional (blue) and transgenic (red) crops in natural habitats. Survival is the fraction of seeds

27 A few baseline thoughts as examples

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29 Gene flow within Swiss crops seed protection experience in Switzerland, Kurt Bodenmüller, Gensuisse Crop breeding system hybridisation potential Hybridization biologie in neighbouring fields with safety distance crop for bred Wheat, summer and winter strictly autogamous very unlikely no/~20m Rye heterogamous very likely minimal/200-1'000m Dinkel + other bred crop strictly autogamous very unlikely no/~20m crop for feed corn for feed auto- and heterogamous possible no/~200m barley strictly autogamous very unlikely no/~20m Oat heterogamous very likely minimal/200-1'000m Triticale strictly autogamous very unlikely no/~20m bred wheat mixture strictly autogamous very unlikely no/~20m Potatoes no fertilization through pollen impossible no/0m Sugar beet no fertilization through pollen impossible no/0m Beet for feed no fertilization through pollen impossible no/0m Gen Suisse, Bern, November 2000/KB

30 Gamma Field for radiation breeding 100m radius 89 TBq Co-60 source at the center Shielding dike 8m high Institute of Radiation Breeding Ibaraki-ken, JAPAN Better spaghettis, whisky 1800 new plants

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34 The way out of unwelcome gene flow in maize

35 Male fertile plant of the maize hybrid Delprim on the left hand side, on the right hand side the male sterile version of the same cultivar. As can be seen from the vestigial inflorescence, the male sterile plant does not release pollen. Photograph by M. Long.

36 Future trends of agriculture

37 Figure 1. A diagrammatic indication of the relationship between economic development and environmental concern. The three primary economic systems of agrarian-, industrial-, and knowledge-based service are indicated with arbitrary indications of wealth and development. SO 2 emission is used merely as an indicator of industrial development and the subsequent environmental concern generated The Population/Biodiversity Paradox. Agricultural Efficiency to Save Wilderness Anthony J. Trewavas Plant Physiology Jan. 2001

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41 Invitation join the network Debate, to

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