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The smallest number of fungi were found on wood, because fungi penetrated into the wood slowly. Possibly more fungi or different fungal composition could be found if the research had continued for a few more months. The average discoloration depth (19.3 mm) was comparable to research in Poland (Kirisits 2010) which showed discoloration depth of 18.5 mm, or Norway (Solheim 1991), which showed a discoloration depth of 19.9 mm seven weeks after colonization. The speed of colonization depended on the percentage of humidity in the wood and consequently depends on the quantity of oxygen and temperature. The first fungus that colonized the tree was E. polonica, followed by O. bicolor, G. penicillata, and O. ainoae (Solheim 1992b). E. polonica tolerated low levels of oxygen and also grew very quickly, which was a good combination for colonization of trees (Solheim 1992b).
Kirisits (2004) anticipated that the host tree had a more important influence on assemblages of fungi than the species of bark beetle investigated. Bark beetles I. typographus and I. amitinus have very similar niches, so we can assume that the fungi associated with these two beetles were similar. The complex of fungi associated with I. typographus was more abundant than that associated with I. amitinus (Kirisits 2004, Repe et. al 2013); however, all fungi associated with I. amitinus could also be found in association with I. typographus. Further investigations, with different methods and different sampling plots may also find other fungi that have not yet been found in association with I. amitinus.
Penicillium spp. and yeast were found as well. Yeasts were found at quite high frequencies in association with I. amitinus bark beetle and its developmental life stages but not in connection with wood. Some investigations have already suggested (Grosmann 1931, Six 2003) that yeast might be an important bark beetles associate. In our research yeast was not as common on wood, which was in accordance with previous research in Norway (Solheim1992b). Contrary to yeast, Penicillium spp. were found to be more abundantly associated with wood.
Our research of ophiostomatoid fungi associated with I. amitinus yielded ten ophiostomatoid fungal taxa. Fungi that were found on bark beetles and its earlier life stages were found on wood after the beetles’ colonization. I. amitinus is a good ophiostomatoid fungi vector and it does inoculate fungi into Norway spruce trees. Like other bark beetles, it lives in association with yeast as well. Fungi assemblage connected with I. amitinus in Norway spruce depend on colonization time, position on the host tree and development stage.
We thank Vlado Petrovič from the Slovenian Forestry Service for help finding a research location and Janko Kuster for permission to use his trees for research and for help with cutting trees. Thanks are also due to Danijel Borkovič for his assistance with the fieldwork. We thank Prof. Dr. Dušan Jurc from the Laboratory of Forest Protection at the Slovenian Forestry Institute for allowing us to use his laboratory to isolate and identify the fungi.
The present study was financed by the Slovenian Research Agency through a Young Research Scheme award to Andreja Repe 1000-07-310117, a grant from Pahernikova ustanova 2015 and research program “Forest biology, ecology and technology” (P4-0107).
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