QTL Mapping for Reproductive Maturity in Lowland Switchgrass Populations.

Switchgrass is developed as a promising cellulosic bioenergy crop due to its multiple agronomic advantages, such as longevity, drought and flooding tolerance, low fertilizer requirement, and relatively high yielding potential on marginal land. Reproductive stage is a key trait in the determining developmental process, consequently affecting biomass production in switchgrass. Accordingly, the objective of this study was to identify genomic regions responsible for reproductive stages in lowland switchgrass. A hybrid population consisting of 179 progeny lines derived from a cross between parents NL94 (♀) × SL93 (♂) and a self-pollinated population of 277 progeny lines from first generation (S1) progeny of NL94, were tested in this study. A numerical scale ranging from 1 to 7 was used to evaluate maturity stages of the two populations. Phenotypes were characterized in September 2012. A total of 175 simple sequence repeat (SSR) markers were genotyped in the hybrid population. Genotypic data of more than 500 SSR markers in the S1 population collected in two previous experiments will be used as well. Marker linkage analysis and QTL analysis were performedusing JoinMap 4 and MapQTL 6, respectively. Two major QTLs were identified on linkage group 2b and 8b in the hybrid population,  while in the selfed population, two major QTL regions occurred on linkage group 2b and 7a. Besides, several other QTLs were observed sporadically at different time points. Among all of these QTL regions, the one on linkage group 2b (between marker nfsg-125 and nfsg-09) has a consistent effect across two populations and different time points. Results from the experiment will be valuable in marker assisted selection and elucidation of genetic mechanisms for reproductive development in lowland switchgrass.