Transcript abundance of enzymes involved in lignin biosynthesis of Eucalyptus globulus genotypes with contrasting levels of pulp yield and wood density

One hundred genotypes of Eucalyptus globulus were ranked according to specific consumption of wood (cubic meters of wood needed to produce 1 ton of pulp). Ten of the most contrasting genotypes were separated in two groups of five clones each; group 1 (G1) with high wood density, high pulp yield, and low specific consumption, and group 2 (G2) with low density, low pulp yield, and high specific consumption. The contrasting genotypes also had significant differences in lignin content, percent syringyl unit composition, and frequency of β-O-4 linkages. Gene expression for phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), 4-coumarate:CoA ligase (4CL) and ferulate 5-hydrolase (F5H) was analyzed in the contrasting genotypes. In both groups, transcript abundance for CAD, PAL, and 4CL were similar and only F5H presented significant differences between groups, with high values in the best ranked genotypes G1 in comparison to G2. Correlations between traits were estimated for lignin content vs. pulp yield (R 2 = 0.97), pulp yield vs. syringyl units (R 2 = 0.82), β-O-4 linkages vs. pulp yield (R 2 = 0.84), and β-O-4 linkages vs. syringyl units (R 2 = 0.97). Correlations between chemical composition and transcript abundance for F5H were calculated, finding correlation values with lignin content (R 2 = 0.81), syringyl units (R 2 = 0.83), and pulp yield (R 2 = 0.81). The measurement of transcript abundance of F5H represents a potential genomic tool for tree improvement programs to select trees with high pulp yield.