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Decay resistance of Siberian larch wood against brown rot fungi - Part 2. The effect of genetic variation
1998 - IRG/WP 98-10287
Wood natural decay resistance is mainly restricted in the heartwood part of tree and based on wood microstructure and chemical composition. However, the variation of decay resistant in different wood species is vide and the effect of genotype on decay resistance of Siberian larch wood grown in Finland is not known. The aim of this work was to find out the variation on decay resistance of Siberian larch from different genotypes using a preliminary screening test based on a malt agar block decay test (a modified EN 113 test). The increment core samples were collected in October 1997 from 53 different clones and the decay tests started in January 1998 and were finished at the end of March 1998. In future, these results can be used to find most decay resistant material for forest tree breeding.
H Viitanen, L Paajanen, T Nikkanen, P Velling


Association of contents of nitrogen and sugars in rubberwood (Hevea brasiliensis) clones with susceptibility to sapstain by Botryodiplodia theobromae, Aureobasidium pullulans and Aspergillus niger
1999 - IRG/WP 99-10307
The purpose of this study was to determine if nitrogen and sugar contents in rubberwood from three selected varieties (clones) rubber trees would affect the rate of colonisation by Botryodiplodia theobromae (a tropical sapstain fungus), Aureobasidium pullulans (a temperate sapstain fungus) and Aspergillus niger (a common mould fungus). Sapstain growth was rated daily until at least 50% mycelial coverage was achieved for 40x20x5mm3 samples from three rubberwood clones (GT1, PB217 and RRIM600) inoculated with the test fungi and incubated in a humidified petri dish assembly under aseptic conditions. All samples had more than 50% coverage of mycelium after 9 days of incubation. The results indicate that the nitrogen content of clone RRIM600 (1.06lmg/g) was significantly higher when compared to that of clone GTI (0.73mg/g) and clone PB217 (0.78mg/g). After oven drying (45°C), clone PB217 contained significantly higher amounts of fructose (5.55mg/g), glucose (2.30mg/g) and total sugar (13.15mg/g), as compared to clone GTI and RRIM600. Clone GTI had the lowest fructose (0.23mg/g), glucose (0.14mg/g), sucrose (2.20mg/g) and total free sugar (2.56mg/g). RRIM600 however had the highest amount of sucrose. B. theobromae spread significantly faster on RRIM600 (4.3 days when >50% mycelial coverage is achieved) than PB217 (5.6 days) or GTI (5.8 days) which is associated with the overall higher nutrient availability in clone RRIM600. Light sanding (down to 1-2mm depth) of sapstain infected samples revealed that deep sapstain typical of B. theobromae remained in the wood, contrasting with the absence of stain by A. pullulans and A. niger (both are typical superficial stainers) in the sanded material.
A J Ashari, J W Palfreyman, A H H Wong


Decay resistance of Siberian larch wood against brown rot fungus. - Part 3. The variation between plus trees and their grafted clones
2000 - IRG/WP 00-10350
The aim of the study was to estimate the variation in the decay resistance of Siberian larch (Larix sibirica Ledeb.) wood using mature plus trees and their grafted clones. Samples were collected with an increment core borer from 11 original plus trees and their 25-year-old grafted seed orchard clones. A typical brown rot fungus, Coniophora puteana (Schum. ex Fr.) Karst. (BAM Ebw. 15), was used as the decaying organism. The mass loss after 6 weeks' incubation was observed. The results showed that the fast growing wood of the grafts was more susceptible to decay than the wood of the original plus tree. The results showed also radial variation within the mature plus tree logs: the inner part of the heartwood was more susceptible to decay than the outer part of the heartwood. The main advantages of decaying the increment core samples were the possibilities to study standing trees, and to screen large numbers of samples at reasonable costs.
H Viitanen, L Paajanen, M Venäläinen, A Harju, P Velling


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