A total of 14 partners from 13 countries (Austria, Belgium, Germany, Italy, New Zealand, Norway, Poland, Portugal, Sweden, Switzerland, Turkey, USA, UK) committed to this project with the aim of gathering current knowledge on seed borne pathogens with a special focus on conifer species of interest for the participant countries and to generate data on the movement of conifer seed, focusing on the most traded conifer genera and/or species. This project also provided the opportunity of comparing and run in parallel testing of seed lots using the traditional and molecular methodologies by participant laboratories with the aim of harmonising methodologies for the detection of pathogens.

An exhaustive review of the literature on seed borne pathogens of conifers was carried out and a total of 153 bibliographic references were collected during the project. The interceptions concerning conifer seeds were extracted for the period 2012-2022 from official sources and a total of 87 "non-compliant" conifer seed interceptions were identified over this period, mostly for administrative problems (incomplete documents). Only one case of interception of Gibberella circinata in 2017 on Pinus taeda seeds originating from USA. Most of the interceptions concerned Pinus seeds.

A database was created of the export and import volumes of tree seed internationally to enable an analysis of trade patterns of conifer seed for planting over time and different analyses were performed and one of the analyses indicates that overall North America is a growing exporter of forest tree seed, especially for south Europe and east Asia.

Seed-associated fungi were recovered from all tree species analysed and with each isolation protocol applied. However, important differences in the incidence of seed-associated fungi as well as in the diversity and composition of the fungal communities were observed among tree species and isolation protocols. In the comparison of culturing-based and HTS methods for detection of conifer seed fungi, the analyses showed that the diversity of seed-borne fungal taxa as revealed by HTS (Illumina MiSeq sequencing) is considerably higher than when assessed by plating the seeds on agar media. Thus, for studies aiming at investigating the diversity of seed-borne fungi a high-throughput amplicon sequencing approach should be applied. However, it should not be forgotten that such an approach does not allow to assess whether the fungi detected are alive or not.

During the duration of this project, researchers from different partners reviewed some scientific articles on seed-borne/transmitted pests on conifers to collaborate with ISTA Reference Pest List project.