Susceptibility of Abies pinsapo and its tree cohort species to Heterobasidion

Abies pinsapo, a rare fir found in the southernmost mountain region of Spain, is severely affected by Heterobasidion abietinum. It was hypothesized that spread of the disease might be favoured by woody species growing in the same habitat. In order to evaluate this hypothesis, artificial inoculation tests were performed on other potential hosts forming the tree cohort species with A. pinsapo. Inoculation test on seedlings demonstrated that H. abietinum was able to colonize stems of Pinus halepensis, P. pinaster and Quercus ilex subsp. rotundifolia, but failed on Q. faginea. Both Pinus species were colonized to a similar extent as the natural host, but Q. ilex subsp. rotundifolia showed a significantly lower susceptibility than conifers. These results suggest that Pinus spp. growing in mixed stands with A. pinsapo might favour spread of H. abietinum. As a consequence, natural replacement of pure A. pinsapo stands by mixed forest Abies-Quercus should be facilitated.