Growth of four bark-beetle-associated blue-stain fungi in relation to the induced wound response in Norway spruce

Abstract

Twenty-five-year-old Norway spruce trees (Picea abies) were inoculated with four blue-stain fungi. Each tree was inoculated three times with each fungus and three times with sterile agar as a control, giving a total of 15 inoculations per tree. There was little variation in the extent of phloem necrosis produced in response to the different fungi, but 5 weeks after inoculation necroses induced by Cerntocystis polorlica and Atnbrosiella sp. were significantly longer than those for the other fungi. At the same time, C. polonica had induced sapwood desiccation twice as deeply into the wood as any other fungus. Hyphal growth of the fungi into phloem and sapwood followed the same pattern as necrosis length and desiccation depth. Five weeks after inoculation, C. polorlica had penetrated phloem and sapwood farther than any other fungus. It grew more slowly than the other fungi in both tissues the first week after inoculation, but the four following weeks it grew more quickly than all other fungi.Resume : Les auteurs ont inocult des tpinettes de Norvkge (Picea nbies) iigtes de 25 ans, avec 4 champignons de la bleuissure du bois. 11s ont inocult chaque arbre trois fois avec cheque champignon, et trois fois avec de I'eau stCrile comme ttrnoins, ce qui a donnt 15 inoculations par abre. Il y a eu peu de variation dans I'Ctendue de la ntcrose du phloeme causte par les difftrents champignons, mais 5 semaines apres l'inoculation, les ntcroses induites par le Ceratocysris polor1ica avec I'Arnbrosiella sp. Ctaient significativement plus longues que celles caustes par les autres champignons. Simultantment le C. polonica a provoqut une dessiccation du bois deux fois plus profonde que tout autre champignon. La croissance des hyphes du champignon dans le phlottme et dans l'aubier suit le meme patron que la longueur de la nCcrose et la profondeur de la dessiccation. Cinq semaines aprks l'inoculation, le C. polorlicn avait pCnCtrC le phloeme et l'aubier plus profondtmcnt que les autres champignons. 11 pousse plus lentement que les autres champignons dans les deux tissus au cours des premieres semaines aprks I'inoculation, mais au cours des quatre semaines suivantes, il pousse plus rapidement que tous les autres.

Xylem dysfunction in Yezo spruce (Picea jezoensis) after inoculation with the blue‐stain fungus Ceratocystis polonica

“…The symptom development was less intensive compared with the results by Yamaoka et al (2000). The rapid enlargement of the desiccated xylem in horizontal and longitudinal directions within 4 weeks after inoculation confirms the observations of Krokene and Solheim (1997) on Norway spruce. The dye injection tests and anatomical studies indicated that sap ascent of the saplings that had been inoculated with C. polonica was considerably reduced or even blocked prior to the appearance of visible foliar symptom and resinosis from inoculation wounds.…”

“…In the present experiment, the distribution of fungal hyphae was very restricted during the early period of infection until appearance of foliar symptoms. The finding that fungal hyphae are not present in the margin of the dry zones at the initiation of needle discolouration is in agreement with Hobson et al (1994) and Krokene and Solheim (1997). The finding that fungal hyphae are not present in the margin of the dry zones at the initiation of needle discolouration is in agreement with Hobson et al (1994) and Krokene and Solheim (1997).…”

“…Necrotic lesions in the phloem around inoculation wounds are clearly not the direct cause of needle discolouration and shoot dieback on spruce trees after infection by C. polonica (Krokene and Solheim 1997). The natural infection with C. polonica originates from numerous wounds initiated in the course of mass attacks of spruce trees by I. typographus (Christiansen and Solheim 1990;Solheim 1992b).…”

Induced responses in stilbenes and terpenes in fertilized Norway spruce after inoculation with blue-stain fungus, Ceratocystis polonica

“…After lowdensity inoculation, however, lesion length alone is not a good measure of the resistance of the tree or of fungal virulence. Here lesion length was about the same as in a lowdensity study in Norway spruce after a corresponding incubation time (Krokene and Solheim 1997). In general, small lesions indicate either the weakness of the aggressor or the resistance of the host.…”

Levinas and Political Theory

“…Similar conclusions have been reached in other studies based on a comparable experimental design , Nagy et al 2000, Krekling et al 2003, Krokene et al 2003. Defense responses of coniferous trees to pathogen infection include rapid cell death and accumulation of secondary metabolites at the infection site (e.g., phenolic and resinous compounds), resulting in discrete necrotic lesions (Berryman 1972, Nicholson and Hammerschmidt 1992, Krokene and Solheim 1997. Tissue discoloration and necrosis are associated with oxidation and polymerization of accumulating phenols.…”