Genetic Control of Flowering in Switchgrass.

Flowering can negatively affect biomass yield of switchgrass. In temperate regions of the USA, flowering occurs in switchgrass around the time of peak biomass yield (about 5 to 8 weeks prior to killing frost), effectively reducing the length of the growing season. The use of late-flowering switchgrass genotypes has proven an effective mechanism to increase biomass production in the northern USA. Southern populations (lowland ecotypes) of switchgrass can be 4–6 weeks later in flowering time than upland types. Selection of late flowering genotypes of southern origin, but under northern conditions, can extend vegetative growth. Late flowering and winter hardy cultivars can have up to a 50% increase in biomass yield in the northern USA, compared to early flowering cultivars. To develop a rational strategy for creating improved switchgrass with late flowering, it would be beneficial to have a better understanding of the genes that control flowering time in switchgrass. Through a genome-wide association study (GWAS) of 1.3 million single nucleotide polymorphisms with 510 diverse individuals from both lowland and upland panels, we have identified 10 genes significantly associated with flowering time. One candidate gene is a homolog of Flowering Locus T (FT). Flowering time of three mapping populations derived from upland (early flowering) and lowland (late flowering) materials are being evaluated in the field in DeKalb, IL and West Lafayette, IN. These mapping populations are being used to create genetic map, identify quantitative trait loci and verify results from GWAS. The results will aid breeding programs in developing late flowering varieties of switchgrass that fully utilize the growing season and achieve high biomass yield.