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Comparison of three methods of quantitative evaluation of sapstain in rubberwood
2000 - IRG/WP 00-20188
Assessing the extent of fungal stain on wood during laboratory trials is a subjective process and is subjected to considerable variation between individual evaluators and specimen. The purpose of this paper was to explore the potential of three quantitative methods of wood surface measurement of rubberwood specimens degraded by sapstain and mould fungui (Botrydiplodia theobromae, Aureobasidium pullulans and Aspergillus niger) and to identify the best possible method for quantitative assessment of sapstain on wood surface. The three methods evaluated were Spectrophotometry (Spectroflash 500), colorimetry (Minolta Croma Meter CR200) and Densitometry. Test samples, 40x20x5mm3 from three rubberwood clones (GT1, PB217 and RRIM600) were inoculated with the test fungi and incubated in a humidified petri dish assembly under aseptic conditions. After four weeks, the stained test samples were air dried and sanded (approximately 0.5mm). The quantitative ratings generated by the colorimeter were the most closely correlated (R 2 = 0.836) with the subjective visual evaluation.
A J Ashari, J W Palfreyman, A H H Wong


White Rot in Eucalyptus Wood: Anatomical Changes and Density Variation by X-Ray Densitometry
2007 - IRG/WP 07-10631
Wood samples of the hybrid Eucalyptus grandis x urophylla attacked by white rot fungi were characterized. Microscopically, the colonization of the fungi was observed in the vessels and radial parenchyma, however the cell walls of the some fibers were attacked, indicating susceptibility to this fungi. Zone lines were observed as a result of interaction and compartmentalization of the fungi. Microscopically, the colonization of the fungi was observed in the cell wall of the wood anatomical components, indicating a preferential attack by white rot fungi, with depletion of lignin and hemicellulose. In the zone lines was characterized the formation of a pseudosclerotial structure, with melanized and branched hyphae into a variety of shapes. Analyses of radiographic images were used to determinate variations in density for the eucalyptus decayed and sound wood. In a quantitative evaluation was observed a loss of density in the wood affected by the white rot fungi (mean, minimum and the maximum wood density decrease of 10, 19 and 7,5 %, respectively) demonstrating the possibility of this technique to estimate strength loss in the wood.
M Tomazello Fo, S Brazolin, M P Chagas