QTL Mapping of Biomass and Forage Quality Traits Measured Using Near-Infrared Reflectance Spectroscopy (NIRS) in Switchgrass

Switchgrass ( Panicum virgatum L.) is a perennial warm-season grass that can serve dual purposes, forage and biofuel feedstock. Because the cell wall accounts for more than half the dry matter weight, breeding for both objectives will largely depend on cell wall components which include cellulose, hemicellulose, and lignin. We used NIRS to measure crude protein, neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose, and Klason lignin to conduct QTL mapping in an F1 population derived from a cross between tetraploid lowlands AP13 and B6 with 285 progenies. Of the three major cell wall components of the dry matter, cellulose was the highest (34.51–41.40%), followed by hemicellulose (25.48–33.55%), and Klason lignin (9.70–13.23%). Mapping of biomass and forage quality traits was done using two linkage maps with 2772 SNP markers. We identified 37 significant QTL for all six traits with the highest percentage variance explained by individual QTL in all traits ranging from 4.89 to 8.57%. There are 9 chromosome regions with colocalized QTL of different traits, indicating either pleiotropic gene action or tight linkage between the genes. Improvement of switchgrass for forage and biofuel feedstock quality would benefit from the selection of QTL that contribute directly to the target phenotypes. The frequency of favorable QTL alleles can be enhanced through Genomic Selection.