Biofuel crops such as napiergrass possess traits characteristic of invasive plant species, raising concern that biofuels might escape cultivation and invade surrounding agricultural and natural areas. Napiergrass biofuel types are being developed to have reduced invasion risk, but these might be cultivated in areas where naturalized populations of this species are already present. The successful management of napiergrass biofuel plantations will therefore require techniques to monitor for escaped biofuels as distinguished from existing naturalized populations. Here we used 20 microsatellite DNA markers developed for pearl millet to genotype 16 entries of napiergrass, including naturalized populations and accessions selected for biofuel traits. Use of the markers showed a clear genetic separation between the biofuel types and naturalized entries and revealed naturalized populations undergoing genetic isolation by distance. These findings demonstrated the utility of microsatellite marker transfer in the development of an important tool for managing the invasion risk of a potential biofuel crop.
Nomenclature: Napiergrass, Pennisetum purpureum Schumach., pearl millet, Pennisetum glaucum (L.) R. Br.
Management Implications: Cellulosic biofuels offer opportunities for sustainable energy production, but many traits of biofuel crop species increase the potential for escape and invasion into surrounding natural areas. Biofuel crop accessions might be selected for high biomass and reduced invasion risk, but management of biofuel plantings will nevertheless require a means to monitor for the escape of cultivated varieties, especially in areas where naturalized populations of the same species are also present. DNA microsatellite markers offer technical and practical advantages for this purpose, including marker transferability. Markers that have already been developed for a crop or model species can be transferred to a related species, sparing the time and cost of marker development. Napiergrass (Pennisetum purpureum) is a crop that has tremendous potential for biofuel production in areas where naturalized populations are already present and creating weed problems. Exploiting napiergrass as a biofuel will require risk management strategies that include a means to genetically track both the cultivated and naturalized types. We found that microsatellite markers developed for pearl millet (Pennisetum glaucum) readily distinguished the naturalized populations of napiergrass collected across the state of Florida from the napiergrass selected for biomass traits. These findings demonstrate that naturalized, weedy populations of napiergrass have a different genetic origin from the biomass types and validate the transferred DNA markers as an effective management tool for distinguishing between the two.