1. Wild Brassicas: a case study Mike Wilkinson

2. The risk assessment process 1.Specify and rank the hazards 2.Quantify generic aspects of exposure 3.Evaluate aspects of exposure specific to one transgene or GM cultivar

3. The risk assessment process 1.Specify and rank the hazards 2.Quantify generic aspects of exposure 3.Evaluate aspects of exposure specific to one transgene or GM cultivar

4. Hazards relating to Gene flow from oilseed rape in the United Kingdom

5. Rank primary recipients Scheffler & Dale (1994) Transgenic Res. 3, 263-278 Brassica rapa B. oleracea B. carinata B. juncea B. nigra B. adpressa Raphanus raphanistrum Diplotaxis erucoides D. muralis

6. Rank primary recipients Scheffler & Dale (1994) Transgenic Res. 3, 263-278 Brassica rapa B. oleracea B. carinata B. juncea B. nigra B. adpressa Raphanus raphanistrum Diplotaxis erucoides D. muralis

7. Oilseed rapeBargeman’s cabbage Brassica napusBrassica rapa

8. GM crop GM F 1 hybrids in region Transgene stabilises by introgression Transgene spreads to most populations

9. Aim To create spatially explicit models of hybridization, introgression and transgene spread

10. Parameterisation needs F 1 hybrid modelling –Frequency of hybrids –Location of hybrids Introgression modelling –Fertility and fitness of hybrids –Past introgression rates for different parts of the genome Transgene spread modelling –Population size and distribution –Demographic baseline data –Gene flow estimates between populations

11. F 1 Hybrid abundance and distribution 1.Local hybrids 2.Long-scale hybrids

12. Local hybrids 1.Where do oilseed rape& B. rapa grow together? 2.How many hybrids form locally?

13. The importance of context

14. Brassica rapa Casuals of disturbed land A weed of B. napus Stable wild populations of river banks

15. Where is oilseed rape?

18. Where is riverside B. rapa? >300km of 8 rivers (Thames, Nene, Avon, Derwent [Yorkshire], Ouse, Soar, The Great Ouse and Trent) and 4 canals surveyed by foot and boat. Survey of herbaria: 601 B. rapa, 138 identified on named river 82 local Floras CEH country-wide survey

19. A. Rapeseed B. Waterside C B. rapa B. rapa within 30m of rapeseed

20. Measure local hybrid frequency

21. DNA fingerprinting Measure DNA content Determine hybrid frequency at sites of co-occurrence Oilseed rape B. rapa Hybrid Oilseed rape B. rapa Hybrid On average 1.46% hybrids per site

22. Calculate long-range hybrid numbers

23. Calculate long range hybrids from.. Separation distance between oilseed rape fields and B. rapa Pattern of decline in airborne pollen quantity with distance Relationship between amount of airborne pollen and hybrid numbers

24. Result 1.We calculate approximately 32,000 hybrids form annually between oilseed rape and riverside B. rapa in the UK 2.Most occur in eastern and central England 3.Riverside hybrids absent from Scotland and Northern Ireland Wilkinson et al. (2003) Science 302, 457-459

25. Key assumption Insect pollination follows the same dispersal pattern as wind-mediated pollination or is unimportant –Unsatisfactory and needs to be resolved

26. Introgression Fitness and fertility of hybrids Effect of integration site

27. Fitness and fertility of hybrids Male fitness –Viable pollen output –Total pollen output –Effectiveness as a male parent Female fitness –Seed return –Seed viability

28. Importance of integration site Select populations where chloroplast capture has occurred (and so introgression has happened previously), Compare introgression rates of selected C- genome and A-genome marker sets that are specific to B. napus

29. Spread between populations Distribution of populations Persistence of visible populations Self-incompatibility Observed gene flow between contemporary populations Seed versus pollen-mediated gene flow

30. Spread between B. rapa populations Population distribution patterns Originally used Literature and surveys to identify rivers carrying B. rapa Survey data to establish patterns of distribution Apply probabilistic approaches to predict B. rapa population distributions

31. But This assumes distributions on tributaries is similar to that on main rivers (where access is possible by footpaths) So –This assumption is being tested by remote sensing using high-resolution aircraft-data

32. Real and False colour images

33. B. rapa mask

34. Population persistence

35. June 2001

36. March 2002

40. Disturb cover in variable populations New B. rapa seedling germinate where plants are absent New B. rapa populations germinate in extinct populations

41. So Presence or absence of plants is variable between years Populations more perhaps accurately defined by seedbank presence

42. Gene flow between generations Time t+1 Seedbank Germinated seeds Seedbank Outgoing seeds Outgoing Pollen Seedbank Incoming Pollen Germinated seeds Incoming seeds Incoming Pollen Time t Germinated seeds Seedbank Outgoing Pollen Key: Sampling Direct transfer Loss from system Inter-population transfer

43. Conclusions Trangene spread comprises three main stages that need to be considered separately: F 1 hybrid production; introgression and secondary spread to other populations Each element affecting gene spread needs to be carefully parameterised After initial parameterisation, there is often a need to collect additional data to correct for or test assumptions made in initial models

44. Thanks BBSRC NERC Perry Foundation Joel Allainguillaume, Michael Shaw, Jeremy Sweet, Luisa Elliott, Carol Norris, Tom Harwood, David Mason, Matt Alexander, Pippa Bell