Geneflow and persistence

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. It has good regional coverage 1 km

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. Brassica napus Brassica rapa Raphanus raphanistrum Sinapis arvensis Common Cruciferae

13. Will OSR affect rest of seedbank ? Community-scale properties

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. Distance and time? 1 km

18. Gene flow depends on context f d

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

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