Awareness, detection and management of new and emerging tree pests and pathogens in Europe: stakeholders' perspectives

Emerging and invasive tree pests and pathogens in Europe are increasing in number and range, having impacts on biodiversity, forest services, ecosystems and human well-being. Stakeholders involved in tree and forest management contribute to the detection and management of new and emerging tree pests and pathogens (PnPs). We surveyed different groups of stakeholders in European countries. The stakeholders were mainly researchers, tree health surveyors and forest managers, as well as forest owners, nurseries, policy-makers, advisors, forestry authorities, NGOs and civil society. We investigated which tools they used to detect and manage PnPs, surveyed their current PnP awareness and knowledge and collated the new and emerging PnP species of concern to them. The 237 respondents were based in 15 European coun-tries, with the majority from the United Kingdom, France and the Czech Republic. There was a strong participation of respondents with a work focus on research and surveying, whereas timber traders and plant importers were less represented. Respondents were surveyed on 18 new, emerging PnPs in Europe and listed an additional 37 pest species and 21 pathogen species as potential future threats. We found that species on EPPO's list of 'priority pests' were better known than those not listed.Stakeholders working in urban environments were more aware of PnPs compared to those working in rural areas. Stakeholders' awareness of PnPs was not related to the number of new, emerging PnP species present in a country. Stakeholders want access to more detection and management tools, including long-term citizen -sci-ence monitoring, maps showing spread and range of new PnPs, pest identification smartphone apps, hand-held detection devices, drone monitoring and eDNA metabarcoding. To help facilitate better forest health across Europe, they called for mixed forest development, reduced nursery stock movement, biosecurity and data sharing amongst organisations. These results indicate that stakeholder knowledge of a few key PnP may be good, but given that the large diversity of threats is so large and future risks unknown, we conclude that multiple and varied methods for generic detection, mitigation and management methods, many in devel-opment, are needed in the hands of stakeholders surveying and managing trees and woodlands in Europe

Marker-Trait Associations for Tolerance to Ash Dieback in Common Ash (Fraxinus excelsior L.)

Common ash (Fraxinus excelsior L.) is a tree species of significant ecological and economic importance that has suffered a devastating decline since the 1990s in Europe. Native ash species are being threatened by the alien invasive fungus Hymenoscyphus fraxineus, which causes ash dieback. The main goal of the study was to develop markers for traits related to tolerance to ash dieback and to investigate whether genotypes selected for tolerance were genetically different from susceptible wild populations. We phenotyped 326 ash trees from Sweden for disease severity and genotyped them using 63 amplicon-derived single-nucleotide polymorphism (SNP) markers derived from genes in 40 scaffolds spanning 8 MB in total, which represents approximately 1% of the ash genome. We used a mixed linear model to test for an association between genotypic variation at these loci and disease severity of ash. In total, two SNPs were found to have significant associations. One non-synonymous SNP associated with the disease severity of ash was found in a gene predicted to encode a subtilisin-related peptidase S8/S53 domain. A second marginally significant marker was associated with an LRR gene. Our results demonstrate an inexpensive time-effective method for generating genomic data that could have potential for use in future tree breeding programs and provide information for marker-assisted selection. Our study also showed a low differentiation between genotypes selected for disease tolerance and the wild population of ash representing a range of susceptibilities to ash dieback, indicating opportunities for further selection without significantly losing genetic diversity in the ash population

Association genetics identifies a specifically regulated Norway spruce laccase gene, PaLAC5, linked to Heterobasidion parviporum resistance

It is important to improve the understanding of the interactions between the trees and pathogens and integrate this knowledge about disease resistance into tree breeding programs. The conifer Norway spruce (Picea abies) is an important species for the forest industry in Europe. Its major pathogen is Heterobasidion parviporum, causing stem and root rot.In this study, we identified 11 Norway spruce QTLs (Quantitative trait loci) that correlate with variation in resistance to H. parviporum in a population of 466 trees by association genetics. Individual QTLs explained between 2.1 and 5.2% of the phenotypic variance. The expression of candidate genes associated with the QTLs was analysed in silico and in response to H. parviporum hypothesizing that (a) candidate genes linked to control of fungal sapwood growth are more commonly expressed in sapwood, and; (b) candidate genes associated with induced defences are respond to H. parviporum inoculation. The Norway spruce laccase PaLAC5 associated with control of lesion length development is likely to be involved in the induced defences. Expression analyses showed that PaLAC5 responds specifically and strongly in close proximity to the H. parviporum inoculation. Thus, PaLAC5 may be associated with the lignosuberized boundary zone formation in bark adjacent to the inoculation site

Combining transcriptomics and genetic linkage based information to identify candidate genes associated with Heterobasidion-resistance in Norway spruce

peer-reviewedThe Heterobasidion annosum s.l species complex comprises the most damaging forest pathogens to Norway spruce. We revisited previously identified Quantitative Trait Loci (QTLs) related to Heterobasidion-resistance in Norway spruce to identify candidate genes associated with these QTLs. We identified 329 candidate genes associated with the resistance QTLs using a gene-based composite map for Pinaceae. To evaluate the transcriptional responses of these candidate genes to H. parviporum, we inoculated Norway spruce plants and sequenced the transcriptome of the interaction at 3 and 7 days post inoculation. Out of 298 expressed candidate genes 124 were differentially expressed between inoculation and wounding control treatment. Interestingly, PaNAC04 and two of its paralogs in the subgroup III-3 of the NAC family transcription factors were found to be associated with one of the QTLs and was also highly induced in response to H. parviporum. These genes are possibly involved in the regulation of biosynthesis of flavonoid compounds. Furthermore, several of the differentially expressed candidate genes were associated with the phenylpropanoid pathway including a phenylalanine ammonia-lyase, a cinnamoyl-CoA reductase, a caffeoyl-CoA O-methyltransferase and a PgMYB11-like transcription factor gene. Combining transcriptome and genetic linkage analyses can help identifying candidate genes for functional studies and molecular breeding in non-model species

Conditions of emergence of the Sooty Bark Disease and aerobiology of Cryptostroma corticale in Europe

The sooty bark disease (SBD) is an emerging disease affecting sycamore maple trees (Acer pseudoplatanus) in Europe. Cryptostroma corticale, the causal agent, putatively native to eastern North America, can be also pathogenic for humans causing pneumonitis. It was first detected in 1945 in Europe, with markedly increasing reports since 2000. Pathogen development appears to be linked to heat waves and drought episodes. Here, we analyse the conditions of the SBD emergence in Europe based on a three-decadal time -series data set. We also assess the suitability of aerobiological samples using a species-specific quantitative PCR assay to inform the epidemiology of C. corticale, through a regional study in France comparing two-year aerobiological and epidemiological data, and a continental study including 12 air samplers from six countries (Czechia, France, Italy, Portugal, Sweden and Switzerland). We found that an accumulated water deficit in spring and summer lower than-132 mm correlates with SBD outbreaks. Our results suggest that C. corticale is an efficient airborne pathogen which can dis-perse its conidia as far as 310 km from the site of the closest disease outbreak. Aerobiology of C. corticale followed the SBD distribution in Europe. Pathogen detection was high in countries within the host native area and with longer disease presence, such as France, Switzerland and Czech Republic, and sporadic in Italy, where the pathogen was reported just once. The pathogen was absent in samples from Portugal and Sweden, where the disease has not been reported yet. We conclude that aerobiological surveillance can inform the spatial distribution of the SBD, and contribute to early detection in pathogen-free countries

Conditions of emergence of the Sooty Bark Disease and aerobiology of Cryptostroma corticale in Europe

The sooty bark disease (SBD) is an emerging disease affecting sycamore maple trees (Acer pseudoplatanus) in Europe. Cryptostroma corticale, the causal agent, putatively native to eastern North America, can be also pathogenic for humans causing pneumonitis. It was first detected in 1945 in Europe, with markedly increasing reports since 2000. Pathogen development appears to be linked to heat waves and drought episodes. Here, we analyse the conditions of the SBD emergence in Europe based on a three-decadal time- series data set. We also assess the suitability of aerobiological samples using a species-specific quantitative PCR assay to inform the epidemiology of C. corticale, through a regional study in France comparing two- year aerobiological and epidemiological data, and a continental study including 12 air samplers from six countries (Czechia, France, Italy, Portugal, Sweden and Switzerland). We found that an accumulated water deficit in spring and summer lower than -132 mm correlates with SBD outbreaks. Our results suggest that C. corticale is an efficient airborne pathogen which can dis- perse its conidia as far as 310 km from the site of the closest disease outbreak. Aerobiology of C. corticale followed the SBD distribution in Europe. Pathogen detection was high in countries within the host native area and with longer disease presence, such as France, Switzerland and Czech Republic, and sporadic in Italy, where the pathogen was reported just once. The pathogen was absent in samples from Portugal and Sweden, where the disease has not been reported yet. We conclude that aerobiological surveillance can inform the spatial distribution of the SBD, and contribute to early detection in pathogen-free countriesinfo:eu-repo/semantics/publishedVersio

Expression analysis of Clavata1-like and Nodulin21-like genes from Pinus sylvestris during ectomycorrhiza formation

The ecology and physiology of ectomycorrhizal (EcM) symbiosis with conifer trees are well documented. In comparison, however, very little is known about the molecular regulation of these associations. In an earlier study, we identified three EcM-regulated Pinus expressed sequence tags (EST), two of which were identified as homologous to the Medicago truncatula nodulin MtN21. The third EST was a homologue to the receptor-like kinase Clavata1. We have characterized the expression patterns of these genes and of auxin- and mycorrhiza-regulated genes after induction with indole-3-butyric acid in Pinus sylvestris and in a time course experiment during ectomycorrhizal initiation with the co-inoculation of 2,3,5-triiodobenzoic acid, an auxin transport inhibitor. Our results suggest that different P. sylvestris nodulin homologues are associated with diverse processes in the root. The results also suggest a potential role of the Clv1-like gene in lateral root initiation by the ectomycorrhizal fungus

Insight into trade‐off between wood decay and parasitism from the genome of a fungal forest pathogen

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91191/1/j.1469-8137.2012.04128.x.pd