Preliminary report on distribution of Heterobasidion annosum intersterility groups in Poland

The study material consists of 165 <i>H. annosum</i> isolates from 25 different localities. Host species was <i>Pinus sylvestris, Picea abies, Betula pendula, Abies alba, Lnrix decidua, Pinus strobus, Prunus serotina, Quercus rubra</i>. Most of the <i>H. annosum</i> isolates belonged to the P group. This group was most common on pine and birch. The S group infected Norway spruce and European fir. The F group was recorded only in the south of Poland. Only three localities, where this intersterility group was present, were found in Poland.

Wie gross wird Heterobasidion annosum s.l.? – Eine Literaturübersicht | Clonal size of Heterobasidion annosum s.l.

We present a literature review on the size of H. annosum s.l.clones. As a rule, the largest diameter of a genet is smaller than 30 m, only in single cases up to 55 m were measured. The maximum age of an individual genet is estimated to around 200 years. The differences between the various intersterility groups and species within H. annosum s.l. are small. Potential factors which may delimit the mycelial life span are discussed.

Relative abundance and potential dispersal range of intersterility groups of Heterobasidion annosum in pure and mixed forests

In Europe the forest pathogen Heterobasidion annosum (Fr.) Bref. includes the S, P, and F intersterility groups (ISGs), each displaying a preferential specialization on Norway spruce (Picea abies (L.) Karst.), pine, and silver fir (Abies alba Mill.), respectively. In this paper, we present data about (i) H. annosum ISGs frequency in different forest types, (ii) the degree of host specificity of each ISG, (iii) the significance of the potential movement of airborne spores among forests, and (iv) the occurrence of S–P chimeras in the northwestern Alps. Using woody spore traps, we sampled natural pure spruce and fir forests and a mixed spruce-fir forest. The ISG of 582 spores was determined by ISG-diagnostic taxon-specific competitive priming (TSCP) polymerase chain reaction (PCR) combined with PCR-mediated detection of ISG-specific introns in the ML5–ML6 DNA region of the mitochondrial large ribosomal RNA (mt LrRNA). All three ISGs were found, and a strong correlation was observed between the F ISG and fir and the S ISG and spruce. In the mixed forest, no clear relationship between tree host species and host-specialized ISGs was found. In spite of a relative dominance of fir in the overstory of the mixed stand, the fir-associated F ISG represented only 11% of the total number of spores collected. This discrepancy was explained by the recent establishment of firs at this site. No S–P nuclear-mitochondrial chimeras were found. This suggests limited gene flow between these ISGs.Key words: Heterobasidion annosum, host specificity, ISGs, gene flow, PCR, Alps.