While Hymenoscyphus fraxineus causes dieback of the European ash ( Fraxinus excelsior ), flowering ash ( F. ornus ) appears resistant to the pathogen. To date, contributions of endophytic fungi to host resistance are unknown. The following hypotheses were tested: (1) endophytic fungi enhance the resistance of F. excelsior to the pathogen; (2) resistance of F. ornus relies on its community of endophytic fungi. Two experiments were performed. (a) The effect of exudates of ash endophytes on the germination rate of H. fraxineus ascospores was studied in vitro. Isolates of abundant Fraxinus leaf endophytes, such as Venturia fraxini, Paraconiothyrium sp., Boeremia exigua, Kretzschmaria deusta and Neofabraea alba inhibited ascospore germination. (b) Ash seedlings inoculated in a climate chamber, with fungi sporulating on the previous year's leaf litter, were exposed to natural infections by the pathogen present in the forest. Non-inoculated seedlings were used as controls. Venturia spp. dominated the inoculated endophyte “communities”. Subsequent exposure to H. fraxineus led to infection of F. excelsior leaves by the pathogen, but no differences in health status between pre-inoculated and non-inoculated seedlings were detected. F. ornus leaves experienced a very low infection rate, independent of their colonization by endophytic fungi. These results did not support either hypothesis.

Regeneration of Picea abies in high-elevation mountain forests often depends on the presence of coarse woody debris (CWD), as logs provide sites with more favorable conditions for spruce regeneration compared to the forest floor. However, there is little quantitative knowledge on the factors that are conducive to or hindering spruce establishment on CWD. We examined spruce regeneration on CWD by sampling 303 plots (50 cm × 50 cm each) on 56 downed logs in a virgin forest in the Swiss Alps. Variables describing microsite conditions were measured, and fungi were isolated from wood samples. To investigate the relationship between the ecological factors and establishment success, two models were fitted with seedling and sapling density as response variables, respectively. Besides log diameter, the models identified different ecological factors as significant for seedling and sapling establishment, i.e., regeneration depends on different factors in different development stages. Seedling density depended on the type of rot, log inclination, and decay stage. Sapling density depended mainly on light availability, cover by bark and moss, the time of tree fall, and the distance between the log surface and the forest floor. A total of 22 polypore fungi were isolated from the wood samples, four of them being threatened species. White- and brown-rot fungi were found in all decay stages. The visual assessment of the type of rot in the field corresponded in only 15% of cases to the type of rot caused by the isolated fungi; hence caution is needed when making field assessments of rot types.

Phialocephala fortinii s.l. and Acephala applanata are the dominant dark septate endophytes (DSE) in roots of many trees and shrubs. Population genetic analysis led to the discovery of morphologically indistinguishable but reproductively isolated cryptic species (CSP) within Phialocephala fortinii s.l. In the present study we show that sequence data of two coding (beta-tubulin and translation elongation factor [EF-1alpha]) and three noncoding DNA loci confirm subdivision of P. fortinii s.l. and allow to differentiate seven CSP of P. fortinii. In addition we show that strains collected throughout Europe can be classified correctly based on these sequence markers. Statistically significant differences in growth response on different media were observed among CSP of P. fortinii and A. applanata. Growth inhibition on MEA amended with 100 mgl⁻¹ cycloheximide had the strongest differential effect of all physiological traits examined. In contrast exoenzyme production (laccase, proteinase, pectinase, phenol-oxidase, amylase, cytochrome oxidase and tyrosinase) rarely helped to differentiate CSP of P. fortinii. However A. applanata was a strong producer of amylases, laccases and proteinases. Based on these data we propose to assign species rank to six CSP of P. fortinii: P. turiciensis, P. letzii, P. europaea, P. helvetica, P. uotolensis, P. subalpina spp. nov. and P. fortinii s.s.