QTLs for biomass and developmental traits in switchgrass (Panicum virgatum)

Genetic and genomic resources have recently been developed for the bioenergy crop switchgrass (Panicum virgatum). Despite these advances, little research has been focused on identifying genetic loci involved in natural variation of important bioenergy traits, including biomass. Quantitative trait locus (QTL) mapping is typically used to discover loci that contribute to trait variation. Once identified, QTLs can be used to improve agronomically important traits through marker-assisted selection. In this study, we conducted QTL mapping in Austin, TX, USA, with a full-sib mapping population derived from a cross between tetraploid clones of two major switchgrass cultivars (Alamo-A4 and Kanlow-K5). We observed significant among-genotype variation for the vast majority of growth, morphological, and phenological traits measured on the mapping population. Overall, we discovered 27 significant QTLs across 23 traits. QTLs for biomass production colocalized on linkage group 9b across years, as well as with a major biomass QTL discovered in another recent switchgrass QTL study. The experiment was conducted under a rainout shelter, which allowed us to examine the effects of differential irrigation on trait values. We found very minimal effects of the reduced watering treatment on traits, with no significant effect on biomass production. Overall, the results of our study set the stage for future crop improvement through marker-assisted selection breeding.