Michigan Conifer Growers’ Perspectives on Disease Management

A survey of commercial nursery and Christmas tree growers was implemented online and by mail in 2018 to understand disease issues and information preferences. Overall, the majority of the respondents reported that they prefer online sources of information and many are using Extension bulletins and sources. Cultural, chemical, and weed control methods were considered extremely effective by participants and very few used biological control methods to control disease. Participants identified spruce decline, boxwood blight, and hemlock woolly adelgid as emerging disease threats, so future information to growers should focus on identification and management of these threats

Anthropogenic disturbances and the dmergence of native diseases : a threat to forest health

PURPOSE OF REVIEW : Human-caused global change is fundamentally altering natural forest ecosystems. More trees are exhibiting a wide range of symptoms indicative of poor vigour, particularly stressed species at the edge of their native ranges and stands growing on marginal sites. This review will focus on complex tree diseases (declines) caused by native pathogens and the key environmental drivers that contribute to this phenomenon. These systems are frequently complex, with multiple drivers at work. RECENT FINDINGS : Using four cases studies on different continents, we explored the direct and indirect environmental drivers underlying these decline syndromes. Although climate and weather events seem to be usually associated with forest decline, we found that environmental disturbance by either forest management or land-use changes is also a global predisposing factor of decline which deserves more attention. Changes in land use have directly benefited pathogens such as root rots in the Pyrenees (Spain) or indirectly by making the environment more conducive for canker and foliar diseases in Australia and the USA. Focus on land-use changes could improve understanding of current decline problems such as those affecting Araucaria in Chile. SUMMARY : The next century will almost certainly see an unprecedented rise in forest pathogen epidemics, requiring a proactive rather than reactive response. Diseases caused by native pathogens with complex aetiologies will become more common, and recognising, characterising and managing these epidemics are difficult because native pathogens are frequently already widespread, and eradication is not feasible. We need to start approaching these issues from a ‘whole ecosystem’ perspective, highlighting the many aspects and entanglements of forest declines and allowing us to respond with management options tailored to each scenario. The approach proposed here provides logical steps based on six questions to untangle the direct and indirect environmental drivers of tree declines.Open Access funding enabled and organized by CAUL and its Member Institutions. The ‘Ramón y Cajal’ fellowship RYC-2015–17459 from the Ministry of Science and Education of Spain and USDA Forest Service Forest Health Protection.https://link.springer.com/journal/40725hj2023BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyPlant Production and Soil Scienc

Independent Evolution Has Led to Distinct Genomic Signatures in Dutch Elm Disease-Causing Fungi and Other Vascular Wilts-Causing Fungal Pathogens

Vascular wilts are important diseases caused by plant pathogenic fungi that result in the rapid death of their plant hosts. This is due to a systemic defense mechanism whereby the plant induces the compartmentalization of the infected vascular system in order to reduce the propagation of the fungus. The ascomycete class Sordariomycetes contains several species that cause vascular wilts in diverse plant hosts, and they can be classified into four taxonomic orders. The genetic mechanisms of pathogenesis have already been investigated in Fusarium and Verticillium species, but they have not yet been compared with other well-known wilt-causing species, especially fungi causing oak wilt or Dutch elm disease (DED). Here we analyzed 20 whole genome assemblies of wilt-causing fungi together with 56 other species using phylogenetic approaches to trace expansions and contractions of orthologous gene families and gene classes related to pathogenicity. We found that the wilt-causing pathogens evolved seven times, experiencing the largest fold changes in different classes of genes almost every time. However, some similarities exist across groups of wilt pathogens, particularly in Microascales and Ophiostomatales, and these include the common gains and losses of genes that make up secondary metabolite clusters (SMC). DED pathogens do not experience large-scale gene expansions, with most of the gene classes, except for some SMC families, reducing in number. We also found that gene family expansions in the most recent common ancestors of wilt pathogen groups are enriched for carbohydrate metabolic processes. Our study shows that wilt-causing species evolve primarily through distinct changes in their repertoires of pathogenicity-related genes and that there is the potential importance of carbohydrate metabolism genes for regulating osmosis in those pathogens that penetrate the plant vascular system

Table_1_Benchmarking a fast and simple on-site detection assay for the oak wilt pathogen Bretziella fagacearum.DOCX

Oak wilt is a vascular disease of oak trees caused by the fungus Bretziella fagacearum. Once infected, trees may die in a few weeks. Although the disease is currently only found in the United States, it has been reported within just a few hundred meters of the Canada–USA border. To limit the establishment and spread of oak wilt in Canada, the development of an on-site, quick and reliable method to detect B. fagacearum is critical. In this study, we developed and validated a new qPCR TaqMan® assay that can detect B. fagacearum in a laboratory setting with great specificity and sensitivity. Using this test as a reference, we also developed and validated a new DETECTR assay that can detect B. fagacearum under 1 h from a variety of environmental samples, such as mycelium mats and insect vectors, using minimal laboratory equipment. While there are still some limitations to the sensitivity of this assay, we believe that its ease of use, flexibility and accuracy will provide an essential tool in efforts to reduce the spread of oak wilt.</p

Table_2_Benchmarking a fast and simple on-site detection assay for the oak wilt pathogen Bretziella fagacearum.DOCX

Oak wilt is a vascular disease of oak trees caused by the fungus Bretziella fagacearum. Once infected, trees may die in a few weeks. Although the disease is currently only found in the United States, it has been reported within just a few hundred meters of the Canada–USA border. To limit the establishment and spread of oak wilt in Canada, the development of an on-site, quick and reliable method to detect B. fagacearum is critical. In this study, we developed and validated a new qPCR TaqMan® assay that can detect B. fagacearum in a laboratory setting with great specificity and sensitivity. Using this test as a reference, we also developed and validated a new DETECTR assay that can detect B. fagacearum under 1 h from a variety of environmental samples, such as mycelium mats and insect vectors, using minimal laboratory equipment. While there are still some limitations to the sensitivity of this assay, we believe that its ease of use, flexibility and accuracy will provide an essential tool in efforts to reduce the spread of oak wilt.</p

Data_Sheet_1_Benchmarking a fast and simple on-site detection assay for the oak wilt pathogen Bretziella fagacearum.PDF

Oak wilt is a vascular disease of oak trees caused by the fungus Bretziella fagacearum. Once infected, trees may die in a few weeks. Although the disease is currently only found in the United States, it has been reported within just a few hundred meters of the Canada–USA border. To limit the establishment and spread of oak wilt in Canada, the development of an on-site, quick and reliable method to detect B. fagacearum is critical. In this study, we developed and validated a new qPCR TaqMan® assay that can detect B. fagacearum in a laboratory setting with great specificity and sensitivity. Using this test as a reference, we also developed and validated a new DETECTR assay that can detect B. fagacearum under 1 h from a variety of environmental samples, such as mycelium mats and insect vectors, using minimal laboratory equipment. While there are still some limitations to the sensitivity of this assay, we believe that its ease of use, flexibility and accuracy will provide an essential tool in efforts to reduce the spread of oak wilt.</p

Genome-Enhanced Detection and Identification (GEDI) of plant pathogens

Plant diseases caused by fungi and Oomycetes represent worldwide threats to crops and forest ecosystems. Effective prevention and appropriate management of emerging diseases rely on rapid detection and identification of the causal pathogens. The increase in genomic resources makes it possible to generate novel genome-enhanced DNA detection assays that can exploit whole genomes to discover candidate genes for pathogen detection. A pipeline was developed to identify genome regions that discriminate taxa or groups of taxa and can be converted into PCR assays. The modular pipeline is comprised of four components: (1) selection and genome sequencing of phylogenetically related taxa, (2) identification of clusters of orthologous genes, (3) elimination of false positives by filtering, and (4) assay design. This pipeline was applied to some of the most important plant pathogens across three broad taxonomic groups: Phytophthoras (Stramenopiles, Oomycota), Dothideomycetes (Fungi, Ascomycota) and Pucciniales (Fungi, Basidiomycota). Comparison of 73 fungal and Oomycete genomes led the discovery of 5,939 gene clusters that were unique to the targeted taxa and an additional 535 that were common at higher taxonomic levels. Approximately 28% of the 299 tested were converted into qPCR assays that met our set of specificity criteria. This work demonstrates that a genome-wide approach can efficiently identify multiple taxon-specific genome regions that can be converted into highly specific PCR assays. The possibility to easily obtain multiple alternative regions to design highly specific qPCR assays should be of great help in tackling challenging cases for which higher taxon-resolution is needed

Horizontal gene transfer and gene dosage drives adaptation to wood colonization in a tree pathogen

Some of the most damaging tree pathogens can attack woody stems, causing lesions (cankers) that may be lethal. To identify the genomic determinants of wood colonization leading to canker formation, we sequenced the genomes of the poplar canker pathogen, Mycosphaerella populorum, and the closely related poplar leaf pathogen, M. populicola. A secondary metabolite cluster unique to M. populorum is fully activated following induction by poplar wood and leaves. In addition, genes encoding hemicellulosedegrading enzymes, peptidases, and metabolite transporters were more abundant and were up-regulated in M. populorum growing on poplar wood-chip medium compared with M. populicola. The secondary gene cluster and several of the carbohydrate degradation genes have the signature of horizontal transfer from ascomycete fungi associated with wood decay and fromprokaryotes. Acquisition andmaintenance of the gene battery necessary for growth in woody tissues and gene dosage resulting in gene expression reconfiguration appear to be responsible for the adaptation of M. populorum to infect, colonize, and cause mortality on poplar woody stems