The Potential for Crop‐to‐Wild Gene Flow in Sorghum in Ethiopia and Niger: A Geographic Survey

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.) Moench], but systematic surveys of the current extent of contact with wild and weedy relatives are lacking. We studied wild and weedy sorghums that are interfertile 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 10 locations during peak flowering of the crop. In all regions, wild and weedy sorghum occurred intermixed with and adjacent to cultivated sorghum. Wild and 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 and 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.

Genetic structure and relationships within and between cultivated and wild sorghum (Sorghum bicolor (L.) Moench) in Kenya as revealed by microsatellite markers

“…bicolor and ssp. verticiliflorum being well documented within and around cultivation in Africa (Dogget and Majisu 1968;Dogget and Prasada Rao 1995;Tesso et al 2008). In a study related to the present one, Mutegi et al hybridisation as has demonstrated between GM oilseed rape (Brassica napus L.) and its wild relatives (Halfhill et al 2004).…”

“…drummondii) (Harlan and De Wet 1972;Dogget 1988). All subspecies of S. bicolor are inter-fertile under sympatric conditions, leading to a continuum of wild-weedy-domesticate complex forms that have been documented to occur in many sorghum growing parts of Africa (Dogget and Majisu 1968;Dogget 1988;Tesso et al 2008;Mutegi et al 2010). Moreover, cultivated and wild sorghum occupy diverse ecological landscapes and have over the years been subjected to diverse biotic and abiotic selection pressures across their geographic range.…”

Genetic variability of sorghum landraces from lower Eastern Kenya based on simple sequence repeats (SSRs) markers

“…All subspecies of S. bicolor are inter-fertile under sympatric conditions, leading to a continuum of wilddomesticate complex forms that have been documented to occur in many sorghum growing parts of Africa (Mutegi et al, 2010;Tesso et al, 2008;Dogget, 1988;Dogget and Majisu, 1968). Therefore, a wide genetic diversity is expected in the landraces of cultivated sorghum in Africa.…”

Sorghum Transformation: Overview and Utility

“…One of the concerns raised about release of transgenic sorghum is the potential for outcrossing to its weedy relatives, johnsongrass and shattercane, which has been hypothesized to potentially lead to altered balance in the ecosystem, changes in the plant community structure, and persistence of weeds in agricultural lands (Tesso et al 2008b).…”