Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/31/2007
Publication Date: 7/1/2008
Citation: Tesso, T., Kapran, I., Grenier, C., Snow, A., Sweeney, P., Pedersen, J.F., Marx, D., Bothma, G., Ejeta, G. 2008. The Potential for Crop-to-Wild Gene Flow in Sorghum in Ethiopia and Niger: A Geographical Survey. Crop Science 48: 1425-1431. Interpretive Summary: With the potential for future development and deployment of transgenic sorghums into centers of origin of the crop, a major concern that needs to be addressed is the extent to which crop-to-wild gene flow occurs in natural populations. This was especially critical for sorghum since in its center of origin, the crop is often grown using traditional farming practices which could place it in close proximity to wild relatives and landraces, and their panicle architecture would be expected to be more amenable to outcrossing than other major cereal progenitors. We found that wild and cultivated sorghums appear in sympatry in all the regions covered in our survey; and that the flowering periods of cultivated and wild sorghums in the region often highly coincide. These observations suggest that pollen mediated gene flow between cultivated and wild sorghums is likely in Africa. The results of our survey suggest that further investigations are needed on the ecological consequences if gene flow occurs between cultivated and wild sorghums.
Technical Abstract: Information about the potential for crop-wild hybridization is needed to understand how crop genes, including transgenes, affect the population genetics and ecology of sexually compatible relatives. Transgenic sorghum is under development for use by traditional farmers in Africa, the center of origin for sorghum (Sorghum bicolor (L.)), but systematic surveys of the current extent of contact with wild and weedy relatives are lacking. We studied wild and weedy sorghums that are inter-fertile with the crop and constitute a crop-wild-weed complex. The survey was conducted in 2005 in areas of traditional sorghum cultivation in three regions of Ethiopia and two regions of Niger. Within each region, we examined eight representative sorghum fields at each of ten locations during peak flowering of the crop. In all regions, wild/weedy sorghum occurred intermixed with and adjacent to cultivated sorghum. Wild/weedy sorghums were detected at 56%, 44%, and 13% of the Ethiopian sites (Amhara, Tigray and Hararghe regions, respectively), and 74% and 63% of sites in Niger (Maradi-Tahoua and Tillabery-Dosso regions, respectively). Flowering periods of wild/weedy sorghum populations overlapped with those of cultivated sorghum at most sites where the two co-occurred, especially in Ethiopia, and many putative crop-wild hybrids were observed. Therefore, current gene transfer from cultivated sorghum to wild and weedy sorghum populations in Ethiopia and Niger is likely to be widespread.