Initial reactions in sapwood of Norway spruce and Scots pine after wounding and infection by Heterobasidion parviporum and H. annosum

Abstract

The xylem surface of seedlings, stem material and roots of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) were inoculated with strains of Heterobasidion annosum s. str. and H. parviporum s. str. The depth of necrosis in wounded spruce increased at a linear rate for at least seven weeks of incubation, but the rate of necrotic spread was significantly faster in infected wounds. In wounded pine the necrosis was maintained at a more superficial level for several weeks. Both spruce and pine sapwood were initially infected by hyphae of both species. In spruce, the hyphae advanced at a constant rate behind the necrotic front. On the contrary, after 1-2 weeks living H. parviporum hyphae were rare in pine rays. Heterobasidion annosum hyphae survived in pine rays, phloem and tracheids, despite a heavy accumulation of phenolics and resins and were able to penetrate into the sapwood at a linear rate although slower than infections in spruce. Histochemistry and quantitative estimates demonstrated that peroxidase activity was initially higher in spruce sapwood than in pine. Within three days of incubation, the activity in spruce sapwood disappeared concurrently with deepening necrosis. However, in pine, in both control and infected samples, there was a significant increase in peroxidase activity in the area surrounding the superficial necrosis, up to the wound surface and in the cambium and phloem around the wound. After wounding and infection, the content of soluble protein increased significantly in wood of older trees but not in seedlings. Infection resulted in an increased formation of lipophilic extractives in both spruce and pine but to a significantly greater degree in the latter, whereas the amount of hydrophilic compounds decreased in both. High-performance liquid chromatography (HPLC) analyses of lipophilic extracts showed that inoculation of pine with the two species of Heterobasidion increased the amounts of pinosylvin, its monomethylether and several other phenolics as also resinous compounds. The results obtained may be relevant in explaining the known higher resistance of Scots pine to H. parviporum.

Phenolic metabolites in the resistance of northern forest trees to pathogens — past experiences and future prospects

“…In a recent study, Blodgett et al (2007) found no correlation between the length of challenge lesions and PSME and concluded that stilbenes may not play a significant role in induced resistance against Sphaeropsis sapinea. Johansson et al (2004) compared the induced responses of Scots pine and Norway spruce after infection with the white rot fungi Heterobasidion annosum and Heterobasidion parviporum. Peroxidase activity was initially higher in spruce sapwood than in pine, but within 3 days of incubation the activity in spruce disappeared concurrently with deepening necrosis.…”

The origin of reactive oxygen during interaction of Pinus sylvestris root and Heterobasidion annosum s.l. – the linkage with the iron

“…All the species can cause severe damage in coniferous forest, endangering the timber production in Europe (Asiegbu et al 2005). Johansson et al (2004) studied H. parviporum infection and showed that peroxidase activity was higher in Picea abies than in Pinus sylvestris. Similarly, an increase in peroxidase transcription was observed in roots of P. sylvestris, infected by H. annosum s.s. (Li and Asiegbu 2004).…”

Accumulation of iron-binding compounds in root of Pinus sylvestris challenged by Heterobasidion annosum sensu lato

“…Different mechanisms of root penetration by various H. annosum s.l. species were also shown by Johansson et al (2004) and confirmed by .…”