Mapping of QTLs Underlying Biomass Yield and Related Traits in Switchgrass.

Switchgrass is a warm season perennial grass identified as a promising dedicated bioenergy crop.  Improvement of biomass yield and cell wall composition traits is paramount to meet the target. Application of molecular markers in breeding programs increases the selection efficiency and gain. With the aim of developing marker-assisted selection (MAS) in switchgrass, quantitative traits loci (QTL) analysis was conducted for biomass yield and related traits using data obtained from several environments on ♀AP13 × ♂VS16 mapping population. The parental linkage maps were constructed using SSR and STS markers. The population showed significant variations in all the traits studied including transgressive segregations. Based on the composite interval mapping, a total of 35 main-effects QTL were identified for each of biomass yield and plant height. The phenotypic variability explained (PVE) by individual QTL range from 4.5-24.0% for biomass yield and from 4.6-30.6% for plant height. A total of 20, 39 and 41 main-effect QTLs were detected for regrowth, heading dates and vegetative growth length, respectively. The PVE ranged from 4.8-23.2, 5.0-51.8, and 4.1-50.3% for regrowth, heading date and vegetative growth length, respectively. QTL with pleiotropic effect that may enable indirect selection for biomass yield via contributing traits were identified. Ten genomic regions important in controlling biomass yield and related traits were identified. The markers anchored the QTLs can be used in MAS breeding to maximize selection gain for biomass yield in switchgrass.