Abstract
In this study, we established a comprehensive genetic map with a large number of progeny from a three-generation hybrid
Populus intercross, and phenotyped the lignin content, S/G ratio and 28 cell wall subcomponents both in stems and roots
for the mapping individuals. Phenotypic analysis revealed that lignin content and syringyl-to-guaiacyl (S/G) ratio using
pyrolysis molecular beam mass spectroscopy (pyMBMS) varied among mapping individuals. Phenotypic analysis revealed
that stem lignin content is significantly higher than that in root and the quantified traits can be classified into four distinct
groups, with strong correlations observed among components within organs. Altogether, 179 coordinating QTLs were
detected, and they were co-localized into 49 genetic loci, 27 of which appear to be pleiotropic. Many of the detected
genetic loci were detected differentially in stem and root. This is the first report of separate genetic loci controlling cell wall
phenotypes above and below ground. These results suggest that it may be possible to modify lignin content and
composition via breed and/or engineer as a means of simultaneously improving Populus for cellulosic ethanol production
and carbon sequestration.
