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

Abstract

The blue-stain fungus Ceratocystis polonica is pathogenic to Norway spruce (Picea abies) in Europe, as well as to Yezo spruce (Picea jezoensis) and Sachalin spruce (Picea glehnii) in Japan. The wilting mechanism in P. jezoensis saplings after inoculation with C. polonica was examined based on anatomical studies of the phloem and xylem of periodically harvested trees. In addition, the course of sap ascent in the trunks was traced by injection of acid fuchsin solution at harvest. As an initial external symptom, needle discolouration was observed. In dye conduction tests, xylem dysfunction in the xylem of inoculated trees became obvious. The dehydrated xylem area (dry zone) had extended more than 20 cm above the inoculation wounds, within 1 month after inoculation. When the sap flow to the branches had nearly stopped, the leaves began to discolour. Hyphae of C. polonica colonized the ray tissue around the inoculation wounds, but were absent at the front of the dry zones. Defence reactions occurred in ray parenchyma cells adjacent to the penetrating hyphae. It is suggested that secondary metabolites, which are formed by the ray cells and epithelial cells of resin canals, are involved in the obstruction of sap flow. Limited necrotic lesions of the phloem and cambium were not associated with foliar symptoms. It is proposed that the dry zone formation caused by C. polonica is the main mechanism leading to tree death.

Susceptibility of longleaf pine roots to infection and damage by four root-inhabiting ophiostomatoid fungi

“…However, following inoculation of host roots, it is clear that significant sapwood damage results from the lesion response, and may lead to significant losses of hydraulic conductivity resulting from tissue occlusion, particularly during periods of strong response. Joseph et al (1998) observed loss of conductivity in roots naturally affected by black-stain root disease and similar findings have been shown experimentally following inoculation of host stems (Kuroda, 2005;Matusick et al, 2008).…”

“…A darkened lesion is commonly observed in conifer hosts around the world following inoculation with ophiostomatoid fungi (Kuroda, 2005;Plattner et al, 2008;Solheim et al, 2001). Increases in oleoresin flow are characteristic in tissues surrounding artificial inoculations (Klepzig et al, 2005;Knebel et al, 2008), particularly following the introduction of highly pathogenic species (Cobb, 1988).…”

The tree species matters: Biodiversity and ecosystem service implications of replacing Scots pine production stands with Norway spruce

“…Bark beetles are also vectors for bluestaining ascomycete fungi (e.g. Endoconidiophora polonica) (Wingfield et al 1993), which further degrades wood quality (Kuroda 2005). Increasing the stem density and prevalence of mature spruce stands is likely to raise the potential for bark beetle outbreaks (Overbeck and Schmidt 2012).…”

Catechol dioxygenases catalyzing the first step in Norway spruce phenolic degradation are key virulence factors in the bark beetle-vectored fungus Endoconidiophora polonica

“…Bark beetles are associated with various species of blue-staining ascomycete fungi that are introduced into the host during an attack (Kirisits, 2010). These blue-stain fungi ultimately grow into the cambium and sapwood of trees, where they occlude the vascular bundles and negatively affect wood quality (Kuroda, 2005). Under severe infestation, this can lead to tree mortality.…”