Gene Flow in African Rice Farmers’ Fields

(eds M.C.S. Wopereis et al.) 95 as the Togo Hills – African rice continues to be present, and is locally important (Barry et al., 2007; Nuijten et al., 2009; Okry, 2011, Teeken et al. 2011; Temudo, 2011). In these older, established areas of rice cultivation, wild rice is sometimes still gathered locally (Richards, 1986; Nuijten, 2005). It is often assumed that in traditional agriculture crops are enriched by gene exchange with wild and weedy relatives (De Wet and Harlan, 1975; Altieri and Merrick, 1987; Prain, 1993), although there seems little hard evidence for the movement of valuable traits from wild relatives into crops (Wood and Lenné, 1997). This, however, does not mean that no new potentially valuable traits arise from introgression (Jarvis and Hodgkin, 1999). Discovering actual gene flow between wild and cultivated species in the field is complicated by the fact that, because of pairing of homologous genes and other processes during meiosis and fertilization, fertile interspecific progenies resemble either the wild or the cultivated species. This is illustrated by research on gene exchange between O. sativa and O. glaberrima that indicates that as the interspecific hybrids are sterile, backcrosses are needed to restore fertility. Therefore, the fertile hybrid derivatives resembled the parental phenotypes (Sano, 1989). This explains why the Introduction