Wood decay caused by Heterobasidion parviporum in juvenile wood specimens from normal- and narrow-crowned Norway spruce

Abstract

Heterobasidion parviporum (Fr.) Niemelä & Korhonen is a serious forest pathogen affecting the quality of Norway spruce (Picea abies (L.) Karst), especially in northern hemisphere. Here, we studied the wood decay caused by this pathogen in small wood specimens of 19-year-old normal (P. abies) and narrow crowned (P. abies f. pendula) Norway spruce trees. After six months of incubation, wood specimens taken next to pith (inner) and bark (outer) at 1 m height from the stem base were measured to obtain the percent dry weight loss. The fungal development was also analyzed using Scanning Electron Microscopy (SEM). We found that the crown type (or genetic entry) had no effects on the weight loss. However, outer wood specimens lost, on average, more weight than inner ones. Similarly, wood density and content of lignans were lower at outer sections, opposite to the free glucose content. Wood density correlated negatively with the weight loss of wood specimens, regardless of crown type. Considering that narrow- and normal-crowned trees responded similarly to H. parviporum wood decay, our findings support the potential use of narrow-crowned Norway spruce in practical forestry since they can produce higher stem yield at very dense plantation and without thinning requirements.

Keywords:

• Crown type
• Heterobasidion parviporum
• Picea abies
• weight loss
• wood density
• wood extractives

Acknowledgements

This research was supported by the Graduate School in Forest Sciences, University of Eastern Finland. We thank the Finnish Forest Research Institute for providing the study material and for facilitating the H. parviporum strain. Also the Gamma-Service Produktbestrahlung Company is acknowledged for the sterilization of the wood samples. Ms Maini Mononen, Mr Jarmo Pennala, and Ms Sanna Ahonen, at the University of Eastern Finland, School for Forest Sciences, are acknowledged for helping with the laboratory work, as well as Dr. Kaija Keinonen, from the Department of Biology. M.Sc. Sebastian von Schoultz from Firma von Schoultz is acknowledged for the analyses of wood extractives. Mr Tommi Itkonen from the Department of Physics and Mathematics, University of Eastern Finland is acknowledged for his help with the SEM photographing. Furthermore, PhD students Helena Puhakka-Tarvainen and Suvi Kuittinen are acknowledged for their support to this research work.