ABSTRACT
The composition of canker mycobiota on spruce trunks was studied in the Lisinsky forestry (Leningrad Oblast). Small cankers or canker parts were placed in a humid chamber. Fungi were identified by morphological features. Sorocybe resinae (Fr.) Fr. and Penicillium glaucoalbidum (Desm.) Houbraken & Samson were the most common. The S. resinae occurrence was 75.9 ± 7.9%. The fungus developed in the surface layers of dried resin, but was not detected in the absence of resin production. The fungus S. resinae was therefore assumed to be a nearly ubiquitous component of the mycobiota of resinous cankers on spruce trunks in Leningrad Oblast. The fungus P. glaucoalbidum has only been observed as a saprotroph in Russia earlier. Weak pathogenic properties were detected in the species in experiments; i.e., P. glaucoalbidum grew on live bark tissues in a humid chamber. Based on its high occurrence (41.4 ± 9.1%), P. glaucoalbidum was identified as a regular component of the microbiota in spruce necrotic canker. Pure cultures of P. glaucoalbidum and Oidiodendron sp. were obtained. To test the respective species as possible causative agents of trunk canker, trunks of 20 spruce trees were inoculated with the fungal cultures in a forest stand. The cultures stimulated resin secretion without causing necrosis to spread beyond the inflicted wound. To better understand the phenomenon, a more detailed study of the biota in necrotic cankers is necessary to perform with a special focus on their nonpathogenic part, which has not received proper attention as of yet.