Gene Flow and its Consequences in Sorghum spp.

Gene flow between crops and their weedy or wild relatives can be problematic in modern agricultural systems, especially if it endows novel adaptive genes that confer tolerance to abiotic and biotic stresses. Alternatively, gene flow from weedy relatives to domesticated crops may facilitate ferality through introgression of weedy characteristics in the progeny. Cultivated sorghum (Sorghum bicolor), is particularly vulnerable to the risks associated with gene flow to several weedy relatives, johnsongrass (S. halepense), shattercane (S. bicolor ssp. drummondii) and columbusgrass (S. almum). Johnsongrass and shattercane are common weeds in many sorghum production areas around the world. Sorghum varieties with adaptive traits developed through conventional breeding or novel transgenesis pose agronomic and ecological risks if transferred into weedy/wild relatives. Knowledge of the nature and characteristics of gene flow among different sorghum species is scarce, and existing knowledge is scattered. Here, we review current knowledge of gene flow between cultivated sorghum and its weedy and wild relatives. We further discuss potential avenues for addressing gene flow through genetic, molecular, and field level containment, mitigation and management strategies to facilitate successful deployment of novel traits in this economically important crop species.