The colonisation of freshly sawn Corsican pine lumber by sapstain and mould fungi was investigated at a sawmill in Hampshire, UK. Three repeat trials encompassing the different seasons of the year were carried out over two years. Results show that fungal colonisation of sawn lumber is dependent on the effect of time of year. Sawlogs were stored for different intervals up to 16 weeks before conversion to boards. Boards were then stored for up to 12 weeks after milling and sampled every 4 weeks to determine the effect of timber ageing on fungal colonisation up to 28 weeks after felling. The metabolic activity of wood cells over the period after felling of the original tree was also measured. It was evident that the defacement of boards reached maximum levels after 12 weeks exposure irrespective of seasonal influences. Initial levels of fungal growth on lumber were reduced if the boards were milled from logs stored for a period prior to conversion. Investigations into the metabolic activity of the wood cells revealed significant levels of respiration taking place up to 28 weeks after felling of the original tree including 12 weeks post-conversion into boards. Boards were used to make a nested stack arrangement allowing plastic tanks top be placed in the centre. The tanks contained a sub-sample of the full-size boards in order to investigate insect activity and effects of gammairradiation. A total of 115 insect species representing 16 of the 34 British orders were collected during the trials. Seventy-two percent of these insects were collected from within the stacks of lumber and investigations using sealed tanks containing boards showed that the insects could influence the fungal colonisation of sawn lumber. Despite the relatively short length of the trials, a succession of insect colonisation from fungivores through to predators and detritivores was recorded. Boards, which were sterilised by gamma-irradiation, were preferentially colonised by mould fungi and subsequent internal staining was confined to the outer surface. Trials with short-length billets allowed the wood-colonising ability of selected sapstain fungi to be investigated under controlled conditions following sterilisation by gamma-irradiation or autoclaving, and storage at 30°C and 20°C. Lesion formation in gamma-irradiated tissue was solely due to the fungus potentially conditioning the wood for colonisation. Colonisation studies also revealed that different fungi exhibit different strategies enabling them to infect timber. Pathogenic species demonstrated a relatively fast initial growth rate to establish themselves before triggering any host anti-fungal responses in the wood. The characteristic lesions created in the billets were investigated using light and electron microscopy to reveal hyphal invasion and or/ wood cell modifications. Respiratory activity of the lesions was elucidated using radioactively labelled glucose allowing the metabolic pathways to be ascertained and demonstrated that wood tissue in the apparently healthy regions adjacent to the lesions reacted as if infected. Future work considers the possibility of biocontrol, using insects in combination with gamma-irradiation of sawn lumber and also further investigations into the reaction zones produced by the fungus growing in the wood.

The mountain pine beetle is associated with a diverse array of fungi. Grosmannia clavigera is the most pathogenic of these fungi. A comparison was made between two methods that have been used to assess fungal pathogenicity. Results were similar for older trees inoculated with G. clavigera using either the alternating flap technique or cork borer method. Using the cork borer method, younger lodgepole pine trees were inoculated with five different isolates of G. clavigera. After a 48 week incubation period, isolates ATCC 18086, B5 and H55 had induced stronger pathogenic indicators compared to isolates KW 1407 and B20. After a 7 week incubation period, only isolate ATCC 18086 had induced stronger pathogenic indicators. Usually, this isolate grew faster at lower temperatures and in a low oxygen environment. Isolate KW 1407 consistently produced milder pathogenic indicators during both incubation periods. Among the non-pathogenic fungal associates of the mountain pine beetle, Ceratocystiopsis minuta may be considered the most important because it is the type species for the genus Ceratocystiopsis. The history of this genus is complicated because no physical specimen exists for C. minuta. The phylogeny of the genus Ceratocystiopsis was evaluated. Many isolates of C. minuta were assessed as potential epitypes. Several isolates of C. minuta from previous work were shown to be misidentified. C. minuta isolate CBS 116796 is recommended for future genetic work within the genus Ceratocystiopsis. For morphological work, using measurements from the literature is recommended since CBS 116796 did not produce fruiting bodies.

The mountain pine beetle is associated with a diverse array of fungi. Grosmannia clavigera is the most pathogenic of these fungi. A comparison was made between two methods that have been used to assess fungal pathogenicity. Results were similar for older trees inoculated with G. clavigera using either the alternating flap technique or cork borer method. Using the cork borer method, younger lodgepole pine trees were inoculated with five different isolates of G. clavigera. After a 48 week incubation period, isolates ATCC 18086, B5 and H55 had induced stronger pathogenic indicators compared to isolates KW 1407 and B20. After a 7 week incubation period, only isolate ATCC 18086 had induced stronger pathogenic indicators. Usually, this isolate grew faster at lower temperatures and in a low oxygen environment. Isolate KW 1407 consistently produced milder pathogenic indicators during both incubation periods. Among the non-pathogenic fungal associates of the mountain pine beetle, Ceratocystiopsis minuta may be considered the most important because it is the type species for the genus Ceratocystiopsis. The history of this genus is complicated because no physical specimen exists for C. minuta. The phylogeny of the genus Ceratocystiopsis was evaluated. Many isolates of C. minuta were assessed as potential epitypes. Several isolates of C. minuta from previous work were shown to be misidentified. C. minuta isolate CBS 116796 is recommended for future genetic work within the genus Ceratocystiopsis. For morphological work, using measurements from the literature is recommended since CBS 116796 did not produce fruiting bodies.

The mountain pine beetle is associated with a diverse array of fungi. Grosmannia clavigera is the most pathogenic of these fungi. A comparison was made between two methods that have been used to assess fungal pathogenicity. Results were similar for older trees inoculated with G. clavigera using either the alternating flap technique or cork borer method. Using the cork borer method, younger lodgepole pine trees were inoculated with five different isolates of G. clavigera. After a 48 week incubation period, isolates ATCC 18086, B5 and H55 had induced stronger pathogenic indicators compared to isolates KW 1407 and B20. After a 7 week incubation period, only isolate ATCC 18086 had induced stronger pathogenic indicators. Usually, this isolate grew faster at lower temperatures and in a low oxygen environment. Isolate KW 1407 consistently produced milder pathogenic indicators during both incubation periods. Among the non-pathogenic fungal associates of the mountain pine beetle, Ceratocystiopsis minuta may be considered the most important because it is the type species for the genus Ceratocystiopsis. The history of this genus is complicated because no physical specimen exists for C. minuta. The phylogeny of the genus Ceratocystiopsis was evaluated. Many isolates of C. minuta were assessed as potential epitypes. Several isolates of C. minuta from previous work were shown to be misidentified. C. minuta isolate CBS 116796 is recommended for future genetic work within the genus Ceratocystiopsis. For morphological work, using measurements from the literature is recommended since CBS 116796 did not produce fruiting bodies. / Forestry, Faculty of / Graduate

In the western regions of North America, mountain pine beetle, Dendroctonus ponderosae Hopk., infestations take a tremendous toll of pines , especially lodgepole pine, Pinus contorta Dougl. var. latifolia Engelm.. Mass attack by the beetles is a devastating event for the trees. As well as girdling the tree, a massive inoculation of blue stain fungus "complex" (composed of several species of Ceratocystis, numerous yeasts and other mycelial fungi) is made beneath the bark. These fungi colonize and destroy the parenchyma tissue system of the host sapwood, primarily the ray parenchyma and resin duct epithelium. A blue stain is produced in the sapwood as a consequence of destruction of the sapwood parenchyma. The stain develops inward through the sapwood, and the transpiration stream is cut off. As more and more sapwood is stained, foliar water stress begins to increase. Foliage however, remains green and apparently healthy for up to 10 months after inoculation. When spring bud break begins the year following beetle attack, terminal buds of blue-stained trees begin to expand, then abort. Soon after, the needles of these trees fade to a reddish brown color. Transpiration stream disruption was not caused by penetration of tracheids by fungal hyphae; tyloses were not observed; nor was microconidial blockage of bordered pits seen. Though resin duct epithelium was eventually destroyed, little resin soaking was observed in the initial blue stained regions. Many bordered pits of tracheids in stained regions appeared to be aspirated, suggesting introduction of embolisms.

No description available.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2001. / Härtill 4 uppsatser.

Bark beetles regulate forest succession by removing weakened or stressed trees and exposing understory species to light from canopy gaps. Subterranean termites are predominate decomposers of coarse woody debris in southern pine forests; however, little is known about their role in forest health and succession. Both groups of insects rely heavily on fungal symbioses to fill their respective ecological niches in southern pine forests. During recent inspections of southern pine timber, we observed that trees in the early stages of bark beetle attack often had subterranean termites in blue-stained portions of the trunk. The frequency of subterranean termite presence in blue-stained areas of trees increased proportionally to the stage of bark beetle attack. However, practically no research has undertaken the challenge of describing how woody resources created by bark beetles are identified and utilized by subterranean termites before any signs of stress are visible. Therefore, this study examined possible facilitative interactions between subterranean termites, bark beetles and their blue-stain fungal associates, and other invertebrates, and investigated the effect of blue-stain fungi on surface properties of wood. Both native (Reticulitermes spp.) and Formosan subterranean termites exhibited a higher feeding preference for blue-stained sapwood than for unstained sapwood in laboratory assays. Native subterranean termites also consumed blue-stained sapwood at a higher rate than decayed wood. This study was the first to demonstrate that wood containing a non-decay fungus could elicit a feeding response from subterranean termites greater than that observed for decayed wood. Additionally, the surface properties of bark beetle-attacked southern pine were initially reduced by blue-stain fungal infection; however, the process of kiln-drying reversed this effect, resulting in a surface that was more conducive to wood product manufacturing.

This work presents a survey of blue-stain fungi found in Northwestern Ontario, characterization of a homing endonuclease gene within Grosmannia piceiperda and finally an examination of the introns and homing endonuclease genes found in the large ribosomal subunit gene in species of Ceratocystis; using molecular techniques and phylogenetic analysis, we studied the molecular evolution of these mobile genetic elements. The blue-stain fungi of Northwestern Ontario were identified based on phylogenic analysis of rDNA internal transcribed spacer region sequences. This data was supplemented with morphological characteristics of the fungal cultures. The second project was an examination of a LAGLIDADG homing endonuclease and its IC2 group I intron. This intron is uniquely positioned within the group I intron-encoded rps3 gene of the large subunit ribosomal RNA gene. The final chapter is an investigation of the large subunit ribosomal RNA gene in species of Ceratocystis. The 3’ segment of this gene contains several novel introns and homing endonuclease genes. There is also much diversity between strains despite their close relation on the rDNA internal transcribed spacer region phylogenetic tree. Further, our data also suggest that the single motif LAGLIDADG homing endonuclease of the rDNA mL1923 intron is likely to be an ancestor to other homing endonucleases in the area. The results of these studies demonstrate the role that these elements play in the genetic diversity observed in the blue-stain fungi.

This work presents a survey of blue-stain fungi found in Northwestern Ontario, characterization of a homing endonuclease gene within Grosmannia piceiperda and finally an examination of the introns and homing endonuclease genes found in the large ribosomal subunit gene in species of Ceratocystis; using molecular techniques and phylogenetic analysis, we studied the molecular evolution of these mobile genetic elements. The blue-stain fungi of Northwestern Ontario were identified based on phylogenic analysis of rDNA internal transcribed spacer region sequences. This data was supplemented with morphological characteristics of the fungal cultures. The second project was an examination of a LAGLIDADG homing endonuclease and its IC2 group I intron. This intron is uniquely positioned within the group I intron-encoded rps3 gene of the large subunit ribosomal RNA gene. The final chapter is an investigation of the large subunit ribosomal RNA gene in species of Ceratocystis. The 3’ segment of this gene contains several novel introns and homing endonuclease genes. There is also much diversity between strains despite their close relation on the rDNA internal transcribed spacer region phylogenetic tree. Further, our data also suggest that the single motif LAGLIDADG homing endonuclease of the rDNA mL1923 intron is likely to be an ancestor to other homing endonucleases in the area. The results of these studies demonstrate the role that these elements play in the genetic diversity observed in the blue-stain fungi.