Ophiostomatoid fungi associated with three spruce-infesting bark beetles in Slovenia

Abstract

Ophiostomatoid fungi can severely affect the health and economic value of Norway spruce trees (Picea abies). Although the diversity of ophiostomatoid species and their associations with insects have been well-investigated in central and northern Europe, little is known about the conditions in south-eastern Europe. This study aims to study the assemblages of ophiostomatoid fungi associated with three bark beetle species (Ips typographus, Ips amitinus, and Pityogenes chalcographus) that infect Norway spruce in Slovenia. Bark beetles were sampled in four phytogeographic regions in Slovenia. The fungi found on the bark beetles were identified based on morphology, DNA sequence comparisons of ITS regions and phylogenetic analysis. The species compositions of the fungal associates of the three insect species were compared and the pairwise associations of the occurrence of the fungal species were analysed. Thirteen different species were found. The most commonly encountered fungal associates of the beetles were Ophiostoma bicolor, Ophiostoma brunneo-ciliatum, Grosmannia piceiperda, Ophiostoma ainoae, Ceratocystiopsis minuta, and Grosmannia penicillata. The composition of the fungal associates differed among the bark beetle species, but not among the phytogeographic regions. This study confirms that ophiostomatoid species are common associates of the investigated bark beetle species. Many ophiostomatoid species have strong host associations. I. typographus and P. chalcographus can act as effective vectors for O. bicolor, O. ainoae, G. piceiperda and O. brunneo-ciliatum, whereas I. amitinus often carries G. piceiperda and C. minuta in Slovenian forests.