Understanding Gene Flow between Cultivated Sorghum (Sorghum bicolor) and Johnsongrass (Sorghum halepense).

Sorghum is a globally important crop and its utilization has been increasing in recent times. Sorghum with bioenergy productivity traits are under development; some of them are generated utilizing transgenic technologies. Herbicide resistance (transgenic or non-transgenic) is also an important trait for sorghum improvement to provide new tools for the management of problematic weeds, especially grasses. Johnsongrass is a weedy relative of sorghum and is an extremely difficult species to control in sorghum fields due to genetic similarities and the lack of selective control options. The longevity of herbicide resistance traits introduced in sorghum are challenged due to the potential for outcrossing and transfer of resistance into johnsongrass. The transfer of traits that could provide adaptive advantage to johnsongrass in the broader environment will also pose challenges. Little is known, however, on the nature and characteristics of gene flow between sorghum and johnsongrass. The objective of this research was to develop a deeper understanding of the nature of outcrossing between the two species under controlled as well as natural field conditions, particularly in both directions (sorghum as a male as well as a female parent). Experiments are being conducted on the impact of genetic background of sorghum as well as johnsongrass on the levels of outcrossing. Further, phenotypic and genetic characteristics as well as fitness of the progeny resulting from such hybridization are being studied. Results are expected to provide novel insights into the nature of gene flow between sorghum and johnsongrass and identify avenues for mitigating gene flow between these species.