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Seed dispersal is an important factor influencing the genetic structure of forest tree populations. Knowledge about the seed shadow is important to assess the ability of tree species to colonize new and disturbed habitats or to respond to environmental change by migrating to more suitable habitats. In a seed trap experiment, we investigated local seed dispersal distances of silver fir seeds (Abies alba Mill.) by explicitly identifying mother trees. For this purpose, we matched microsatellite genotypes of maternal tissues of seeds with the genotypes of adult trees in the studied stand. Furthermore, we analysed the effect of morphological traits on dispersal distance, and we assessed the number of contributing mother trees and compared the seed density of the closed forest-stand with the adjacent blowdown. Based on 674 seeds collected in a grid of 37 seed traps, a significant decline in seed density was observed from within the forest to the forest blowdown area [40 m from the forest edge. A median dispersal distance of 31 m was determined for filled seeds based on direct assignment of seeds to their mother trees. This was higher than that determined in the previous studies using different methods. Dispersal distance was negatively correlated to seed-weight, but this was partially compensated for by the length of seed wings. A very large number of unassigned maternal genotypes (435) suggested that dispersal distance might have been underestimated. Lessons for future studies were: to perform a full genotypic inventory of adult trees in a defined perimeter, to increase the number of microsatellite markers and to study several sites over a period of several years.

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Ash dieback, caused by the pathogen Hymenoscyphus pseudoalbidus, is an emerging lethal disease of Fraxinus excelsior in large parts of Europe. To develop a method for the early detection of H. pseudoalbidus, we designed primers for 46 microsatellites (simple sequence repeats, SSRs) of the pathogen. Seven pairs of primers (SSR38, SSR58, SSR114, SSR198, SSR206, SSR211 and SSR212) were found to bind only to the genome of H. pseudoalbidus, but not to the genome of H. albidus or to 52 different fungal endophytes isolated from F. excelsior and F. angustifolia. Using these seven primer pairs, H. pseudoalbidus was identified in fruiting bodies and different types of ash tissues including dead leaves, dead petioles and discoloured or non-discoloured wood. Along one twig, H. pseudoalbidus was detected at different levels of intensity, which depended on the distance from symptomatic tissue. The detection limit was 0.9-1.8 pg of genomic DNA per PCR. Of 50 analysed commercially available seedlings, six were infected with H. pseudoalbidus. Two SSR loci (SSR198 and SSR211) showed fragment length polymorphism. Our results showed that the new primers not only provide an easy and inexpensive means of detecting H. pseudoalbidus in ash tissues, but can also provide information on the genetic heterogeneity of the species.