A new publication from GenØk shows that maize farming by smallholders, for local food production, is particularly vulnerable to the introduction of genetically modified (GM) maize. The reason is that the fields are situated very close to each other (distance often 2-5 m) and that pollen will cross-hybridize at a high rate. In addition, farmers recycle their seeds year after year and share seeds with neighbors and family. Seed sharing may transfer viable seeds up to 100 km.

The study performed fieldwork in Zambia, uses mathematical modelling of pollen spread and interviewed farmers about their seed management practices. Globally, 85 % of all farms are small-scale (< 2ha).

The study concludes that segregation of GM and non-GM maize varieties is likely not an option in these systems. If GM maize is introduced, farmers will contribute to uncontrolled spread of GM maize. One further negative effect is that cross-hybridization of GM (Bt-maize) and non-GM maize may give increased risk of resistance development in pest insects

For further questions or information contact:

Thomas Bøhn (PhD), GenØk

Reference
Bøhn, T., Aheto, D. W, Mwangala, F. S., Fischer, K., Bones, I. L., Simoloka, C., Mbeule, I., Schmidt, G. and Breckling, B. (2016). “Pollen-mediated gene flow and seed exchange in smallscale Zambian maize farming, implications for biosafety assessment“, Scientific Reports 6, Article number: 34483. DOI:10.1038/srep34483 (open access)

Abstract
Gene flow in agricultural crops is important for risk assessment of genetically modified (GM) crops, particularly in countries with a large informal agricultural sector of subsistence cultivation. We present a pollen flow model for maize (Zea mays), a major staple crop in Africa. We use spatial properties of fields (size, position) in three small-scale maize farming communities in Zambia and estimate rates of cross-fertilisation between fields sown with different maize varieties (e.g. conventional and transgene). As an additional factor contributing to gene flow, we present data on seed saving and sharing among farmers that live in the same communities. Our results show that: i) maize fields were small and located in immediate vicinity of neighboring fields; ii) a majority of farmers saved and shared seed; iii) modeled rates of pollen-mediated gene flow showed extensive mixing of germplasm between fields and farms and iv) as a result, segregation of GM and non-GM varieties is not likely to be an option in these systems. We conclude that the overall genetic composition of maize, in this and similar agricultural contexts, will be strongly influenced both by self-organised ecological factors (pollen flow), and by socially mediated intervention (seed recycling and sharing).

Photo: © AdobeStock Dusan Kostic