Effect of lignin genetic modification on wood anatomy of aspen trees

Abstract

The directed modification of specific traits of trees through genetic engineering provides opportunities for making significant genetic improvements to wood properties in matter of years instead of extended time frames required for traditional natural selection. An attractive target of forest-tree engineering is the modification of lignin content and lignin structure. While lower lignin content improves pulping efficiency, a decrease in lignin content could affect wood characteristics that are critical for solid wood use. After one year of growth in a greenhouse, a total of forty transgenic aspen (Populus tremuloides Michx.) with reduced lignin content and increased syringyl to guaiacyl ratio were harvested and diameter growth and cell morphology were investigated using quantitative wood anatomy and fiber quality analysis techniques. Comparing genetic groups to the wild-type as the control, similar radial growth and quantitative anatomical properties were observed for the genetic group with reduced lignin content. The genetic group with increased S/G ratio had lower diameter growth, lower vessel lumen diameter, but more numerous vessels. The simultaneous change in lignin content and lignin structure had no effect on radial growth but had the most severe effect on cell morphology. The two genetic lines within this genetic group gave inconsistent results.