Wood Discolouration Research Articles

Short-term effects of remedial surgery to restore productivity to Eutypa lata infected vines

Eutypa dieback, caused by the wood infecting fungus Eutypa lata, causes a gradual decline in vineyard production. Many growers renew infected vines by removing infected wood. Here we report on the short-term effects of the procedure on 28-year-old own-rooted Shiraz vines. In spring 1999, all vines in six adjacent rows were examined for foliar symptoms of Eutypa dieback. The following winter, cuts were made through both cordons and the trunk of each vine to determine the extent of wood discolouration, a symptom of E. lata infection. Foliar symptoms were recorded on 35% of the 141 vines, yet discoloured wood was observed in all cuts made through the cordons and in 71% of cuts made through the trunk. However, no association was found between the foliar symptoms observed in the spring prior to surgery and the extent of wood discolouration, i.e. discolouration that was visible on the cut surface of the trunk (P=0.20). Furthermore, discoloured wood remaining in the trunk had no effect on the production of watershoots (P=0.74), which were produced by 63% of vines in 2000. When re-examined in spring 2001 and 2002, watershoots were observed on 61 and 76% of vines respectively. As in the previous year, no association was observed between the discoloured wood remaining in the trunk and the production of watershoots (P=1.00 in 2001, P=0.21 in 2002). Foliar symptoms were not observed in 2000, 2001 nor in 2002. Infection with E. lata was confirmed by isolation of the pathogen from 92% of discoloured wood samples taken from 14 vines.

Pathogenicity of fungi associated with a decay of kiwifruit

A decay of kiwifruit was noted for the first time in 9 to 10-year-old Italian vineyards. Trunk and cordons of symptomatic vines showed decayed areas surrounded and preceded by wood discolouration. Fomitiporia mediterranea (syn. F punctata) was recovered from decayed tissue, whereas Phaeoacrernonium parasiticum, Cadophora malorum and strains of Phaeoacrernonium aleophilum were found in the discoloured wood. Two-year-old potted kiwifruit vines of the cultivar Hayward were inoculated with a strain of each species in order to assess their ability to cause wood discolouration and decay. Six months after inoculation, discolouration was clearly evident in all plants inoculated with Phaeoacrernonium species and C. malorum. Decayed areas caused by F mediterranea were observed only in some potted plants either 15 or 18 months after inoculation. Some of the vines inoculated with P. aleophilum, C. malorum and F mediterranea shrivelled up completely. Inoculated fungi were always recovered from the discoloured and decayed tissue. Both types of wood deterioration observed in the field on diseased plants were reproduced in the pathogenicity tests.

Birch (Betula pendula) Wood Discolouration during Drying. Effect of Environmental Factors and Wood Location in the Trunk

Summary Birch wood discolours during artificial drying, which is a considerable problem for the use of birch as raw material in the mechanical wood industry. In this investigation sample boards of Betula pendula were sawn to the dimensions used as raw material for parquet billets. The variables studied were those that may affect wood discolouration: growing site, felling date, length of the storage period for logs and location of the wood in the trunk. Discoloration of birch wood was studied in conventional and vacuum drying processes. The wood layer of about 2–5 mm under the yellow surface of conventionally dried boards remained light-coloured, while the inner wood of the boards became discoloured. During vacuum drying, however, the inner wood of sample boards clearly became discoloured. The radial location of the wood in the trunk affected the colour of dried wood more than the longitudinal location did. To keep the colour of dry wood as light as possible, it may be best to fell birch in winter and store the wood for several weeks before conventional drying. On the other hand, the lightest coloured wood obtained during vacuum drying was from autumnfelled five weeks stored birches, which may indicate differences in the process of discoloration in these two drying methods.

Three-Year Observation of Grapevines Cross-Inoculated with Esca-Associated Fungi

Cross-inoculation experiments were carried out in southern Italy (Apulia) on grapevines cv. Italia and Matilde in order to study interactions among the white rot fungus Fomitiporia punctata (Fop) and two tracheiphilous hyphomycetes, Phaeoacremonium aleophilum (Pal) and Phaeomoniella chlamydospora (Pch), commonly associated with esca and brown wood-streaking of grapevine. In January 1999 the three fungi were inoculated through wounds on the trunks and spurs of cv. Italia, and branches and spurs of cv. Matilde. Pch, Pal and Fop were inoculated singly or in groups of two or three in all possible combinations. From the results so far obtained, the following conclusions can be drawn: 1. all three fungi are pathogenic; 2. inoculation of the above fungi on standing grapevines produces symptoms on trunks, shoots, leaves and berries that are reminiscent of those shown by esca-affected vines in the vineyard. In particular, symptoms in the wood (brown streaking, gummosis or “black goo”, and wood decay or white rot), and on the leaves (various forms of chlorosis, reddening and necrosis, distortion of the lamina) and berries (black measles) were reproduced; 3. severity of internal symptoms, assessed as length of brown streaks and intensity of colour change of the infected wood, varied with the growth and interactions between the inoculated fungi; 4. the wood streaking which developed after inoculation with Pal or Pch on the spurs extended to the supporting shoot or branch, and even to the stem; 5. a non-synergistic, competitive association of the two hyphomycetes, and an inhibition of Fop growth by Pal was observed in planta. A similar marked antagonistic effect of Pal against Fop was previously shown to occur when examining interactions between the three fungi in vitro; 6. the wood discolouration caused by Fop was not hampered by Pch, but it is always limited by Pal; 7. on the basis of internal symptoms, grapevines cv. Italia were more susceptible to the esca fungi than grapevines cv. Matilde.

An hydroxynaphtalene reductase gene from the wood-staining fungus Ophiostoma floccosum complements the buff phenotype in Magnaporthe grisea

To understand the mechanism of wood discolouration employed by the staining fungus Ophiostoma floccosum, a gene involved in dihydroxynaphthalene (DHN) melanin biosynthesis was cloned from this organism and its function was examined. Degenerate oligonucleotide primers were designed according to conserved regions of hydroxynaphthalene (HN) reductases and used to PCR-amplify a 380 bp fragment from genomic DNA of O. floccosum. The amplified product was used as a probe to screen an O. floccosum genomic phage library. A genomic clone containing a full-length HN reductase gene was retrieved and a total of 1681 bp of its nucleotide sequence was determined. The determined sequence contained 673 bp of 5’ untranslated sequence, 807 bp of putative open reading frame (ORF) encoding a protein of 269 amino acids and 197 bp 3’ untranslated sequence. The ORF contained a 76-bp intron. Based on the similarity of the inferred amino acid sequence to other known fungal HN reductases, the cloned O. floccosum gene was considered an HN reductase gene. Disruption of the O. floccosum reductase gene was unsuccessful due to integration anomalies during homologous recombination. As an alternative, we complemented an HN reductase deficient buf mutant of the rice blast fungus Magnaporthe grisea by introducing the cloned O. floccosum reductase gene using hygromycin B resistance plasmid pCB1004. The complemented M. grisea buf mutants produced a black pigment like a wild type strain, indicating that the O. floccosum reductase is functionally homologous to other fungal HN reductases. These results suggest that O. floccosum uses the DHN pathway for pigmentation.

Are there genetic differences in susceptibility of Eucalyptus nitens and E. regnans stems to defect and decay?

Summary Levels of spread of wood discolouration and incipient decay associated with artificial stem wounds were studied in a provenance trial of Eucalyptus regnans and a progeny trial of E. nitens. Natural incidence of discolouration and numbers and sizes of kino veins were also examined in a provenance × fertiliser interaction trial in E. regnans. No differences were found between provenances of E. regnans for degree of spread of discolouration despite significant differences in tree diameter. However, incidence and size of kino veins differed between provenances of E. regnans. For E. nitens the spread of discolouration was less than that in E. regnans, and there were no significant differences in discolouration amongst the 10 open-pollinated families, or associated with tree diameter. Heritability estimates for lateral and longitudinal spread in E. nitens were relatively low and had large errors attached due to the small number of families sampled. Degree of lateral spread was correlated with tree diameter in E. regnans but not in E. nitens. Nitrogen fertiliser did not appear to influence defect levels in E. regnans. However, adding phosphorus fertiliser was associated with fewer and smaller kino veins in disc samples removed from the base of the green crown.