1. Geneflow and persistence Geoff Squire Scottish Crop Research Institute

2. Concerns Ecological feral populations or hybrids with wild relatives interfere with the habitat Food purity outcrossing between nearby fields feral populations contributing to yield

3. The system Soil - genesis, resilience Primary production – crops and weeds Decomposition – bacteria, fungi, protozoa, nematodes, collembola, etc. Element cycling Herbivory – nematodes, insects, cattle/sheep + humans

4. The scales Fine soil structure – bacterial, fungal Field patch – plant populations Field – management unit Farm or group of farms Landscape

5. Soil is a complex medium

6. Oilseed rape Reappeared as a common crop in 1970s Most Brassica napus, some B. rapa As a ‘break’ crop in cereals Oil has a wide range of uses Outcrossing (contact, wind, insect) Feral descendents (pod shatter, inducible dormancy)

8. It has joined joined the seedbank In this small plot of 200 m -2 10,000 original OSR crop plants >100,000 seed shed at harvest 100 feral plants one year later >1000 feral seeds still in the seedbank

9. 1 km It has good regional coverage

10. 1. Will it disturb the habitat? Soil structure Habitat processes Other organisms

11. Other arable plants Seedbank – 1000 to >10,000 individuals in a square metre 10 target weeds 30 common, 150 less common species Non-target species highly valuable to arable food web From glacial and more recent

12. Common Cruciferae Brassica napusBrassica rapa Raphanus raphanistrumSinapis arvensis

13. Will OSR affect rest of seedbank ? Community-scaleproperties

14. Will it affect transmission through food webs ?

15. Ecological impact - conclusions Ferals and hybrids - Negligible effect on integrity of soil Negligible effect on main habitat processes Mainly fill vacant space – ferals typically 100 m -2 But might alter seedbank species abundance or species composition And some transmission of effect to food web

16. 2. Impurities in yield Distance and frequency Persistence over time Food quality Perception and preference

17. 1 km Distance and time?

18. Gene flow depends on context f d

19. 2 km Green – oilseed rape fields Black – GM oilseed rape fields Analysis in progress (2002)

20. Impurities in OSR decay slowly

21. Impurity in yield - conclusions Not preventable in oilseed rape under present arable cropping –at low frequency over several km, mediated by a range of insect vectors and wind-borne pollen –regional process depending on the configuration of fields in a locality –cross pollination between nearby fields is 1 in 1000 or less (higher to fields of partial male fertility) –In-field ferals can contribute more (i.e. 1 in a 100) to impurities Can be limited < 0.1% not practicable < 1% uncertain and only with the most rigorous standards

22. Conclusions Of ferals and hybrids – Ecological effects small Low level of impurity in harvest will be difficult to manage First conclusion might have to be modified if field practice changes