| Abstract: | In this study the phylogeographic variation among isolates of the Sirococcus conigenus P group and the phylogenetic relationships of S. conigenus with Sirococcus clavigignenti‐juglandacearum and other species previously placed in the genus Sirococcus were investigated. A collection of 33 isolates originating from Picea, Pinus and Larix in Europe, North America and Bhutan were characterized by sequence analyses of the internal transcribed spacer (ITS) region (including ITS1, 5.8S ribosomal DNA, ITS2) of the nuclear rDNA and a portion of the β‐tubulin gene. In phylogenetic analyses most isolates from pine, spruce and larch formed a distinct clade, representing the P group of S. conigenus, which was separated from the T group of this pathogen. Four isolates from Picea in Europe and Canada formed a third clade within S. conigenus and these isolates are referred to as the S group. The P group consisted of five distinct ITS haplotypes, which partly differed in their optimum growth temperature and their growth rates at 25°C on malt extract agar. Nested clade analysis resolved the five haplotypes into three distinct clades and revealed significant genetic/geographic associations for some of the haplotypes. Parsimony analysis of the small subunit (18S) ribosomal DNA sequences confirmed the phylogenetic affinities between S. conigenus and S. clavigignenti‐juglandacearum. In contrast, Godronia cassandrae and Hormococcus conorum, which formerly had been placed in the genus Sirococcus, were found to be only distantly related to S. conigenus and S. clavigignenti‐juglandacearum. |
