Host and cell type affect the mode of degradation by Meripilus giganteus

• Published in: The New phytologist Vol. 139; no. 4; pp. 721 - 731
• Main Authors: SCHWARZE, F. W. M. R., FINK, S.
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.08.1998; Blackwell
• Subjects: Basidiomycota; Biological and medical sciences; cavities; Cell growth; Cell walls; Fagus sylvatica; fibres; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Fungi; Hyphae; Lignin; Parenchyma; Pathology, epidemiology, host-fungus relationships. Damages, economic importance; pectin; Phytopathology. Animal pests. Plant and forest protection; soft rot; Tension wood; tension‐wood fibres; Tilia platyphyllos; White rot; Wood; Xylem; tension-wood fibres; White rot; fibres; soft rot; cavities; pectin; Wood fiber; Cellulose; Basidiomycetes; Host agent relation; Delignification; Pectin; Fagaceae; Cell wall; Tilia platyphyllos; Fungi; Degradation; Optical microscopy; Cavity; Dicotyledones; Tiliaceae; Angiospermae; Hardwood forest tree; Spermatophyta; Thallophyta; Fagus sylvatica
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1046/j.1469-8137.1998.00238.x

Wood degradation by the white-rot basidiomycete Meripilus giganteus (Pers.: Pers.) Karst. was studied in naturally infected and artificially inoculated wood of beech (Fagus sylvatica L.) and large-leaved lime (Tilia platyphyllos Scop.). Semi-thin sections revealed that the secondary walls of most fibres contained internal cavities. Three distinct types of cavity formation, which differed not only between hosts, but also between cell type and location in the annual ring, were identified. Within discoloured wood of naturally infected beech, the structure of the cavities and their formation by the associated hyphae were reminiscent of a soft-rot. By contrast, cavity formation in artificially inoculated beech and large-leaved lime wood differed from a soft-rot mode of attack as extensive delignification always preceded cavity formation, and neither T-branching, L-bending, nor hyphal growth were found within cell walls. The formation of half-moon shaped cavities in beech wood was present only in tension-wood fibres. From large diameter hyphae, growing within the fibre lumen, numerous fine perforation hyphae extended transversely via helical cracks into the cell wall. Subsequent degradation of cellulose within concentric layers of the tension-wood fibres commenced from the apices of perforation hyphae. Sections stained with ruthenium red and hydroxlamine-ferric chloride, revealed that M. giganteus preferentially degrades pectin-rich regions of the middle lamellae in xylary ray cells. In large-leaved lime, such regions were uniformly located in the middle lamellae of axial and ray parenchyma. In beech wood, degradation of pectin-rich middle lamellae regions commenced after the delignification of secondary walls and resulted in a conspicuous hollowing of multiseriate xylem rays. Plasticity in wood degradation modes by M. giganteus in large-leaved lime and beech wood reflects variations in cell wall structure and/or prevailing wood conditions.