QTL Mapping for Reproductive Maturity in Lowland Switchgrass Populations

Switchgrass (Panicum virgatum L.) has potential to be a major cellulosic bioenergy crop. Selection for late flowering plants will extend the vegetative growth, likely resulting in larger biomass yields. However, the genetic structure for reproductive maturity in switchgrass is undefined. Accordingly, the major objective of this study was to identify genomic regions associated with reproductive development. Two lowland populations, one consisting of 176 progeny from NL94 (♀) × SL93 (♂) and a first-generation self-fertilized population of 265 progeny from NL94, were field established in a randomized complete block design with three replications at two Oklahoma locations in 2011. Phenotypic data of reproductive maturity in the populations were collected in 2012 and 2013. Significant genetic variation for reproductive maturity was observed within the two populations. Broad-sense heritabilities were 0.46 to 0.77 and 0.28 to 0.74 for the hybrid and selfed populations, respectively. A linkage map with 178 simple sequence repeat (SSR) markers of the hybrid population constructed in this study and a pre-existing linkage map of 439 SSR markers in the selfed population were used for quantitative trait loci (QTL) characterization. QTL analyses revealed that reproductive maturity was controlled by multiple genomic regions. The QTL regions between nfsg-125 and PVE-781/782 on linkage group (LG) 2b, between PVGA-1727/1728 and PVGA-1201/1202 on LG 3b, and between PVCAG-2503/2504 and PVAAG-3253/3254 on LG 7a were associated with reproductive maturity in both populations. The markers linked to the significant QTL could be used to accelerate the development of switchgrass germplasm with later flowering to increase biomass yield.