Coexistence between GM and non – GM crops

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Stella Nhahala – 07/2014

1. What is meant by coexistence between GM and non-GM crops?
2. Why is there a need for coexistence between GM and non-GM crops?
3. How is coexistence achieved?
4. How do we develop appropriate guidelines and regulations for coexistence?
5. What is Gene movement?
6. What conditions are necessary for gene flow to occur via cross pollination between GM and non-GM crops?
7. What factors can influence gene flow through pollen transfer?
8. How is pollen flow between plants facilitated?
9. What are the factors that can limit pollen flow?
10. What is isolation distance?
11. How does gene movement occur by seed dispersal?
12. What are natural agents of seed dispersal?
13. How does the seed production and distribution system influence adventitious mixing?.
14. How can adventitious mixing be minimized?
15. Examples of coexistence between GM and non-GM crops
16. Table 2 – GM crops that are under development for future production in Africa

Table 2 – GM crops that are under development for future production in Africa

GM cropMode of PropagationMode of pollinationAgents of pollinationAgents of seed dispersalRecommended Isolation distance (m) for pure seed production (1%)
Banana (Musa spp.) underground stem (corm) cultivated bananas are sterile insects (but cultivated bananas are sterile)none required, the flowers are sterile
Cassava, Manioc, Yuca (Manihot esculenta Crantz) stem cuttings predominately cross-pollination, limited self-pollination in varieties with many branchesinsects and wind insects and animal 30 1,2
Cotton (Gossypium hirsutum L.) Seed predominately self-pollination insects wind, , animals, and water 8100 – 200 1,3
Cowpea (Vigna unguiculata (L.) Walp.) Seed predominately self-pollination insects Dehiscent pods, ants, birds, and rodents 501
Maize/corn (Zea mays L.) Seed cross-pollination Wind animals 2001,3
Potato (Solanum tuberosum L. Tubers self- and cross-pollination insects 201,4,5
African rice (Oryza glaberrima) Seed predominantly self-pollination insects and wind buried in soil, water and animals 1003,6*
Asian rice (Oryza sativa L.) Seed predominately self-pollination insect and wind buried in soil, water and animals 1003,6
Sorghum (Sorghum bicolor (L.) Merr.) Seed predominately self-pollination wind wind, water and animals 200- 4003
Sweet Potato (Ipomoea batatas (L.) Lam.) vine cuttings predominately cross-pollination but rarely flower insects Birds and water No report of pollen studies1,7

* based on Oryza sativa L. data.

1 Andersson, M.S. and Vicente, M.C. foreword by Ellstrand, N.C. (2010) Gene Flow between Crops and Their Wild Relatives. The Johns Hopkins University Press. Bartimore. Maryland

2 Halsey, M.E., Olsen, K.M., Taylor,N.J and Chavarriaga-Aguirre, P. (2008) Reproductive Biology of Cassava (Manihot esculenta Crantz) and Isolation of Experimental Field Trials. Crop Sci. 48:49–58 (2008). doi: 10.2135/cropsci2007.05.0279

3 OECD (2013) OECD Schemes for the Varietal Certification or the Control of Seed Moving in International Trade.

4 Conner, A.J., and Dale, P.J. (1996) Reconsideration of pollen dispersal data from field trials of transgenic potatoes. theor Appl Genet, 92: 505-508.

5 Conner, J. (2006) Biosafety Evaluation of transgenic Potatoes: Gene flow from transgenics Potatoes. International Symposium.

6 Messeguer, J., Fogher, C., Guiderdoni, E., Marfà, V., Català, M.M., Baldi, G. and Melé, E. (2001a) Field assessments of gene flow from transgenic to cultivated rice (Oryza sativa L.) using a herbicide resistance gene as tracer marker. Theor Appl Genet. 103:1151–1159

7 Haberle, S.G., and Atkin, G. (2005) Needles in a haystack: searching for sweet potato (Ipomoea batatas (L.) Lam.) in the fossil pollen record. In: Ballard, C., P. Brown, R.M. Bourke and T. Harwood (eds.). The sweet potato in Oceania: a reappraisal. Ethnology Monograph 19, Oceania Monograph 56; Stucky, J.M., and R. Beckmann, 1982. Pollination biology, self-incompatibility, and sterility in Ipomoea pandurata (L.) G.F.W. Meyer (Convolvulaceae). American Journal of Botany, 69(6): 1022-1031.