BRC Science Highlight Many genomic positions in switchgrass contribute to flowering time, a major biomass yield determinant Objective Gain a better understanding of the genetic regulation of flowering time in switchgrass to aid the development of higher biomass yielding switchgrass cultivars, particularly at northern latitudes Approach Using exome-capture sequencing, perform genome-wide association studies using flowering time data from a switchgrass association panel Use principal component analysis (PCA) to evaluate the population structure of the samples in the study Identify genetic loci associated with flowering time Result/Impacts PCA shows that the 509 switchgrass genotypes in the study represent five genetically distinct regional gene pools. Heading date (as a metric for flowering time) varies between gene pools; in particular, the lowland south gene pool flowers substantially later than the other regional pools. Candidate genes involved in flowering time include known flowering regulators and also genes not previously associated with the control of flowering time (including a homolog of a key circadian regulator). Flowering time variation in switchgrass is due to variation at many positions across the genome. The relationship of flowering time and geographic origin indicates likely roles for genes in both the photoperiod and autonomous pathways in generating switchgrass flowering time variation. Notes: text Title again: Text 1-2 sentence summary? Genetic associations with heading date across the switchgrass genome. Grabowski, P.P. et al. “Genome-wide associations with flowering time in switchgrass using exome-capture sequencing data.” New Phytologist 213, 154-169 (2017) [DOI: 10.1111/nph.14101]. GLBRC December 2016