DNA polymorphism and molecular diagnosis in Inonotus spp.

Specific polymerase chain reaction (PCR) primers were developed for the internal transcribed spacer (ITS) region of the rDNA gene of Inonotus tomentosus, the causal agent of tomentosus root rot of conifers. The primers were designed to specifically amplify DNA from I. tomentosus and allow its differentiation from Inonotus leporinus and from Phellinus pini s.l., which are morphologically very similar to L tomentosus in culture. The PCR amplification was carried out successfully from DNA extracted from fruiting bodies and cultures and can potentially be used to detect the pathogen from environmental samples for survey and management purposes. The PCR assay was validated with 42 samples from seven coniferous hosts originating from eight provinces or states across the North American continent. No cross reaction was observed with DNA of several other species of the same genus, with Phellinus pini or with white spruce (Picea glauca), a conifer host of I. tomentosus. Phylogenetic analysis of the ITS region for six species of Inonotus suggests that these resulted from the adaptation of a generalist ancestor to different ecological niches. It also appears that divergent evolution of an ancestor occupying different ecological niches has driven the speciation process, which subsequently conferred specificity to either coniferous or deciduous trees.