Determination of tree to tree variation in syringyl/guaiacyl ratio of Eucalyptus globulus wood lignin by analytical pyrolysis

High syringyl/guaiacyl ratios (S/G ratios) are advantageous for pulping. Analytical pyrolysis was applied to Eucalyptus globulus wood to measure S/G ratios and assess its potential in forest breeding programmes. Samples were collected from five trees of two provenances grown in three sites. After peak assignment, relative peak areas were calculated for carbohydrate, guaiacyl and syringyl type degradation products. Lignin derived products account on average for 21% of the total identified area. The average S/G ratio of trees was 2.0, ranging from 1.5 to 2.6. The analysis of variance for the S/G ratios showed that provenance and tree were highly significant sources of variation accounting for 48 and 27% of the variation, respectively. Site had no influence but 'site x provenance' interaction was significant and accounted for 16% of the variation. The error associated with the method represented only 6% of the variation. Analytical pyrolysis proved reproducible and sensitive for the measurement of the natural variability of E. globulus with regard to lignin composition. The pyrolytic determination of the S/G ratios is recommended as an evaluation trait in breeding programmes for pulpwood production. (C) 1999 Elsevier Science B.V. All rights reserved.