Gene flow matters in switchgrass ( Panicum virgatum L.), a potential widespread biofuel feedstock

There currently exists a large push for the use, improvement, and expansion via landscape modification of dedicated biofuel crops (feedstocks) in the United States and in many parts of the world. Ecological concerns have been voiced because many biofuel feedstocks exhibit characteristics associated with invasiveness, and due to potential negative consequences of agronomic genes in native wild populations. Seed purity concerns for biofuel feedstock cultivars whose seeds would be harvested in agronomic fields also exist from the agribusiness sector. The common thread underlying these concerns, which have regulatory implications, is gene flow; thus detailed knowledge of gene flow in biofuel crop plants is important in the formulation of environmental risk management plans. Here, we synthesize the current state of knowledge of gene flow in an exemplary biofuel crop, switchgrass ( Panicum virgatum L.), which is native to eastern North America and is currently experiencing conventional and technological advances in biomass yields and ethanol production. Surprisingly little is known regarding aspects of switchgrass pollen flow and seed dispersal, and whether native populations of conspecific or congeneric relatives will readily cross with current agronomic switchgrass cultivars. We pose that filling these important gaps will be required to confront the sustainability challenges of widespread planting of biofuel feedstocks.