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
fi elds at each of 10 locations during peak
fl owering 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 TillaberyDosso
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.