Selection for Winter Survivorship in Lowland Switchgrass

Development of switchgrass (Panicum virgatum L.) as a sustainable biomass crop for conversion to bioenergy requires substantial increases in biomass yield. Because switchgrass is highly photoperiodic, one approach toward this goal is to collect germplasm populations from the Southern USA, then screen and select them in northern environments where they represent a delay in flowering time of up to 6 weeks compared with local ecotypes. This delay in flowering has been linked to increases in biomass yield of up to 50%. The objective of this study was to conduct and evaluate selection progress for winter survivorship in 14 southern lowland populations of switchgrass. The populations originated from USDA Plant Hardiness Zones (PHZ) 7 or 8 (mean annual extreme minimum temperature = − 12.2 °C) and the selection and evaluation were conducted in PHZ 4 or 5 (mean annual extreme minimum temperature = − 28.8 °C). Seven of the 14 populations responded to selection, with increases in winter survivorship and/or biomass yield across four evaluation locations. Winter survivorship and biomass yield were highly correlated with each other, so that increases in survivorship usually translated to increases in biomass yield. The top-ranked population represented the third cycle of selection within the cultivar Kanlow, indicating that the greatest gains from selection represented longer-term efforts than a single generation of field-based selection. This study verified that alleles for winter survivorship and plants capable of surviving in PHZ 4 or 5 can be found across a broad geographic area in the Southern USA, albeit at very low frequencies in most populations.