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The overall goal of the project was to bring together scientists, practitioners and official national bodies (NPPOs) to share knowledge on two important quarantine diseases of trees in Europe: Ceratocystis platani and Cryphonectria parasitica. The threats posed by Ceratocystis platani are often underestimated and even in countries where the disease already occurs, not much measures are taken to limit the spread of this devastating disease. The project contributed to: Improve knowledge on the distribution of Cryphonectria parasitica in European countries. It was shown that C. parasitica is present in Belgium and United Kingdom, but not in Ireland. In the Netherlands, the fungus was found several times on imported Castanea stakes/fences in 2018, but not in nurseries or public green. Develop a collection of C. parasitica isolates. The isolates were used to determine the population structure of C. parasitica in Europe. Evidence was found that in countries where the pathogen was relatively recently described (e.g. UK), the pathogen was introduced several times but has not spread widely, possibly due to suboptimal climatic conditions. Organise a test performance study (TPS) for the real-time PCR test from Pilotti et al. (2012) for the detection of C. platani in wood. Specifically, EvaGreen, SYBR Green and Taqman tests were validated. Standard curves confirmed that the tests have high amplification efficiency. For analytical sensitivity, all laboratories detected 15 and 3 fg C. platani gDNA, thus reproducing the previously reported detection threshold of the method. Testing blind samples yielded a 100% scoring sensitivity, accuracy and specificity in all the experiments, with an exception in the SYBR Green test for which results from one laboratory were nonconforming for the criterion of accuracy.

Oospores of Phytophthora ramorum were produced from intraspecific pairings between a European A1 and European or American A2 strains. Their viability was evaluated through colouration with tetrazolium bromide. The distribution of oospores in the different classes of colouration was similar to that found in other Phytophthora species (homothallic and heterothallic): most of the oospores stained purple, which corresponds to spores in dormancy. In order to produce single-oospore cultures, a method was developed to separate oospores from mycelium and chlamydospores. Germination of oospores was observed in 110, 250, 350 and 500-d-old cultures at a low proportion. Microsatellite marker analyses on oospore progenies revealed that the oospores resulted from hybridisation. More than 50 oospore progenies were characterised in terms of mating type, aggressiveness on Rhododendron leaves, and growth rate on two different media. The results are discussed in the context of pest risk analysis.