Šķipars, V. and Ruņģis, D. 2011. Detection of Heterobasidion annosum in Scots pine trees using a polymerase chain reaction based method.  Baltic Forestry 17(1): 2 – 7

The fungal complex Heterobasidion annosum s.l. (sensu lato) is the major cause of root and butt rot of conifers in the Northern Hemisphere. There is evidence of a genetic component in the resistance of conifers to this fungus. In order to study the genetic basis of resistance in Scots pine, information about the infection level of trees growing in forest stands is important, in combination with data about genotypes or gene expression profiles. Symptoms of H. annosum root rot in living trees are not unique and can be very similar to symptoms caused by other diseases. Additionally, infected P. sylvestris trees can stay asymptomatic for long periods. Therefore, in order to assess the levels of H. annosum infection in forest stands, a direct method for the detection of this pathogen in living Scots pine trees is required. In this paper we present results of detection of H. annosum DNA in living Scots pine trees using a polymerase chain reaction (PCR) assay. A preliminary assay of 300 trees, analysing one sample per individual, revealed 119 trees positive for H. annosum DNA. A more detailed examination of two excavated tree trunks and partial root systems revealed a heterogeneous distribution of H. annosum within pine. Twenty five trees were further chosen for more detailed determination of infection level analysing five samples per individual. The distribution of H. annosum around the stem base of Scots pine trees was found to be heterogeneous, however, the determination of the infection level was found to be reproducible. This study provides a method for rapid, PCR-based determination of H. annosum infection levels both in pine stands and individuals

Key words: Heterobasidion annosum, root rot, species-specific PCR detection