- Home
- A-Z Publications
- Annual Review of Phytopathology
- Previous Issues
- Volume 57, 2019
Annual Review of Phytopathology - Volume 57, 2019
Volume 57, 2019
-
-
Lessons from a Life in Time and Space
Vol. 57 (2019), pp. 1–13More LessA research career investigating epidemiological and evolutionary patterns in both natural and crop host–pathogen systems emphasizes the need for flexibility in thinking and a willingness to adopt ideas from a wide diversity of subdisciplines. Here, I reflect on the pivotal issues, research areas, and interactions, including the role of science management, that shaped my career in the hope of demonstrating that career paths and collaborations in science can be as diverse and unpredictable as the natural world in which we study our organisms of choice.
-
-
-
Fusarium graminearum Trichothecene Mycotoxins: Biosynthesis, Regulation, and Management
Vol. 57 (2019), pp. 15–39More LessFusarium head blight (FHB) of small grain cereals caused by Fusarium graminearum and other Fusarium species is an economically important plant disease worldwide. Fusarium infections not only result in severe yield losses but also contaminate grain with various mycotoxins, especially deoxynivalenol (DON). With the complete genome sequencing of F. graminearum, tremendous progress has been made during the past two decades toward understanding the basis for DON biosynthesis and its regulation. Here, we summarize the current understanding of DON biosynthesis and the effect of regulators, signal transduction pathways, and epigenetic modifications on DON production and the expression of biosynthetic TRI genes. In addition, strategies for controlling FHB and DON contamination are reviewed. Further studies on these biosynthetic and regulatory systems will provide useful knowledge for developing novel management strategies to prevent FHB incidence and mycotoxin accumulation in cereals.
-
-
-
Paving the Way to Tospovirus Infection: Multilined Interplays with Plant Innate Immunity
Vol. 57 (2019), pp. 41–62More LessTospoviruses are among the most important plant pathogens and cause serious crop losses worldwide. Tospoviruses have evolved to smartly utilize the host cellular machinery to accomplish their life cycle. Plants mount two layers of defense to combat their invasion. The first one involves the activation of an antiviral RNA interference (RNAi) defense response. However, tospoviruses encode an RNA silencing suppressor that enables them to counteract antiviral RNAi. To further combat viral invasion, plants also employ intracellular innate immune receptors (e.g., Sw-5b and Tsw) to recognize different viral effectors (e.g., NSm and NSs). This leads to the triggering of a much more robust defense against tospoviruses called effector-triggered immunity (ETI). Tospoviruses have further evolved their effectors and can break Sw-5b-/Tsw-mediated resistance. The arms race between tospoviruses and both layers of innate immunity drives the coevolution of host defense and viral genes involved in counter defense. In this review, a state-of-the-art overview is presented on the tospoviral life cycle and the multilined interplays between tospoviruses and the distinct layers of defense.
-
-
-
Revisiting the Concept of Host Range of Plant Pathogens
Vol. 57 (2019), pp. 63–90More LessStrategies to manage plant disease—from use of resistant varieties to crop rotation, elimination of reservoirs, landscape planning, surveillance, quarantine, risk modeling, and anticipation of disease emergences—all rely on knowledge of pathogen host range. However, awareness of the multitude of factors that influence the outcome of plant–microorganism interactions, the spatial and temporal dynamics of these factors, and the diversity of any given pathogen makes it increasingly challenging to define simple, all-purpose rules to circumscribe the host range of a pathogen. For bacteria, fungi, oomycetes, and viruses, we illustrate that host range is often an overlapping continuum—more so than the separation of discrete pathotypes—and that host jumps are common. By setting the mechanisms of plant–pathogen interactions into the scales of contemporary land use and Earth history, we propose a framework to assess the frontiers of host range for practical applications and research on pathogen evolution.
-
-
-
Mangroves in the Leaves: Anatomy, Physiology, and Immunity of Epithemal Hydathodes
Vol. 57 (2019), pp. 91–116More LessHydathodes are organs found on aerial parts of a wide range of plant species that provide almost direct access for several pathogenic microbes to the plant vascular system. Hydathodes are better known as the site of guttation, which is the release of droplets of plant apoplastic fluid to the outer leaf surface. Because these organs are only described through sporadic allusions in the literature, this review aims to provide a comprehensive view of hydathode development, physiology, and immunity by compiling a historic and contemporary bibliography. In particular, we refine the definition of hydathodes.We illustrate their important roles in the maintenance of plant osmotic balance, nutrient retrieval, and exclusion of deleterious chemicals from the xylem sap. Finally, we present our current understanding of the infection of hydathodes by adapted vascular pathogens and the associated plant immune responses.
-
-
-
Current Status of Potato Cyst Nematodes in North America
Vol. 57 (2019), pp. 117–133More LessThe potato cyst nematodes (PCNs) Globodera rostochiensis and Globodera pallida are internationally recognized quarantine pests. Although not widely distributed in either the United States or Canada, both are present and are regulated by the national plant protection organizations (NPPOs) of each country. G. rostochiensis was first discovered in New York in the 1940s, and G. pallida was first detected in a limited area of Idaho in 2006. In Canada, G. rostochiensis and G. pallida were first detected in Newfoundland in 1962 and 1977, respectively, and further detections of G. rostochiensis occurred in British Columbia and Québec, most recently in 2006. Adherence to a stringent NPPO-agreed-upon phytosanitary program has prevented the spread of PCNs to other potato-growing areas in both countries. The successful research and regulatory PCN programs in both countries rely on a network of state, federal, university, and private industry cooperatorspursuing a common goal of containment, management/eradication, and regulation. The regulatory and research efforts of these collaborative groups spanning from the 1940s to the present are highlighted in this review.
-
-
-
Stealth Pathogens: The Sooty Blotch and Flyspeck Fungal Complex
Vol. 57 (2019), pp. 135–164More LessSooty blotch and flyspeck (SBFS) fungi produce superficial, dark-colored colonies on fruits, stems, and leaves of many plant genera. These blemishes are economically damaging on fruit, primarily apple and pear, because they reduce the sale price of fresh fruit. Fungicide spray programs can control SBFS but are costly and impair human and environmental health; thus, less chemically intensive management strategies are needed. Although the scientific study of SBFS fungi began nearly 200 years ago, recent DNA-driven studies revealed an unexpectedly diverse complex: more than 100 species in 30 genera of Ascomycota and Basidiomycota. Analysis of evolutionary phylogenetics and phylogenomics indicates that the evolution of SBFS fungi from plant-penetrating ancestors to noninvasive ectophytic parasites was accompanied by a massive contraction of pathogenicity-related genes, including plant cell wall–degrading enzymes and effectors, and an expansion of cuticle-degradation genes. This article reviews progress in understanding SBFS taxonomy and ecology and improving disease management. We also highlight recent breakthroughs in reconstructing the evolutionary origins of these unusual plant pathogens and delineating adaptations to their ectophytic niche.
-
-
-
Genome Editing, Gene Drives, and Synthetic Biology: Will They Contribute to Disease-Resistant Crops, and Who Will Benefit?
Vol. 57 (2019), pp. 165–188More LessGenetically engineered crops have been grown for more than 20 years, resulting in widespread albeit variable benefits for farmers and consumers. We review current, likely, and potential genetic engineering (GE) applications for the development of disease-resistant crop cultivars. Gene editing, gene drives, and synthetic biology offer novel opportunities to control viral, bacterial, and fungal pathogens, parasitic weeds, and insect vectors of plant pathogens. We conclude that there will be no shortage of GE applications to tackle disease resistance and other farmer and consumer priorities for agricultural crops. Beyond reviewing scientific prospects for genetically engineered crops, we address the social institutional forces that are commonly overlooked by biological scientists. Intellectual property regimes, technology regulatory frameworks, the balance of funding between public- and private-sector research, and advocacy by concerned civil society groups interact to define who uses which GE technologies, on which crops, and for the benefit of whom. Ensuring equitable access to the benefits of genetically engineered crops requires affirmative policies, targeted investments, and excellent science.
-
-
-
Boxwood Blight: Threat to Ornamentals
Vol. 57 (2019), pp. 189–209More LessBoxwood blight, caused by Calonectria pseudonaviculata and Calonectria henricotiae, has had devastating effects in gardens since its first appearance in the United Kingdom in 1994. The disease affects two other plants in the Buxaceae: sweet box (Sarcococca spp.) and pachysandra (Pachysandra spp.). C. pseudonaviculata was likely introduced to Europe by nursery trade from East Asia on an ornamental species and then to western Asia and North America. Thus far, C. henricotiae has been seen only in Europe. Boxwood, valued at $126 million wholesale per year in the United States alone, is now besieged by an aggressive foliar blight active over a broad temperature range when there are long periods of leaf wetness. Research on inoculum, means of dissemination, cultivar susceptibility, environmental influences, fungicides, sanitizers, and detection methods has vastly improved knowledge of this new invasive disease in a short time. Boxwood with genetic resistance to the disease is critically needed.
-
-
-
Plant Virus Vectors 3.0: Transitioning into Synthetic Genomics
Vol. 57 (2019), pp. 211–230More LessPlant viruses were first implemented as heterologous gene expression vectors more than three decades ago. Since then, the methodology for their use has varied, but we propose it was the merging of technologies with virology tools, which occurred in three defined steps discussed here, that has driven viral vector applications to date. The first was the advent of molecular biology and reverse genetics, which enabled the cloning and manipulation of viral genomes to express genes of interest (vectors 1.0). The second stems from the discovery of RNA silencing and the development of high-throughput sequencing technologies that allowed the convenient and widespread use of virus-induced gene silencing (vectors 2.0). Here, we briefly review the events that led to these applications, but this treatise mainly concentrates on the emerging versatility of gene-editing tools, which has enabled the emergence of virus-delivered genetic queries for functional genomics and virology (vectors 3.0).
-
-
-
Pathways of DNA Transfer to Plants from Agrobacterium tumefaciens and Related Bacterial Species
Vol. 57 (2019), pp. 231–251More LessGenetic transformation of host plants by Agrobacterium tumefaciens and related species represents a unique model for natural horizontal gene transfer. Almost five decades of studying the molecular interactions between Agrobacterium and its host cells have yielded countless fundamental insights into bacterial and plant biology, even though several steps of the DNA transfer process remain poorly understood. Agrobacterium spp. may utilize different pathways for transferring DNA, which likely reflects the very wide host range of Agrobacterium. Furthermore, closely related bacterial species, such as rhizobia, are able to transfer DNA to host plant cells when they are provided with Agrobacterium DNA transfer machinery and T-DNA. Homologs of Agrobacterium virulence genes are found in many bacterial genomes, but only one non-Agrobacterium bacterial strain, Rhizobium etli CFN42, harbors a complete set of virulence genes and can mediate plant genetic transformation when carrying a T-DNA-containing plasmid.
-
-
-
Durability of Quantitative Resistance in Crops: Greater Than We Know?
Vol. 57 (2019), pp. 253–277More LessQuantitative resistance (QR) to crop diseases has usually been much more durable than major-gene, effector-triggered resistance. It has been observed that the effectiveness of some QR has eroded as pathogens adapt to it, especially when deployment is extensive and epidemics occur regularly, but it generally declines more slowly than effector-triggered resistance. Changes in aggressiveness and specificity of diverse pathogens on cultivars with QR have been recorded, along with experimental data on fitness costs of pathogen adaptation to QR, but there is little information about molecular mechanisms of adaptation. Some QR has correlated or antagonistic effects on multiple diseases. Longitudinal data on cultivars’ disease ratings in trials over several years can be used to assess the significance of QR for durable resistance in crops. It is argued that published data likely underreport the durability of QR, owing to publication bias. The implications of research on QR for plant breeding are discussed.
-
-
-
Molecular Dialog Between Parasitic Plants and Their Hosts
Vol. 57 (2019), pp. 279–299More LessParasitic plants steal sugars, water, and other nutrients from host plants through a haustorial connection. Several species of parasitic plants such as witchweeds (Striga spp.) and broomrapes (Orobanche and Phelipanche spp.) are major biotic constraints to agricultural production. Parasitic plants are understudied compared with other major classes of plant pathogens, but the recent availability of genomic and transcriptomic data has accelerated the rate of discovery of the molecular mechanisms underpinning plant parasitism. Here, we review the current body of knowledge of how parasitic plants sense host plants, germinate, form parasitic haustorial connections, and suppress host plant immune responses. Additionally, we assess whether parasitic plants fit within the current paradigms used to understand the molecular mechanisms of microbial plant–pathogen interactions. Finally, we discuss challenges facing parasitic plant research and propose the most urgent questions that need to be answered to advance our understanding of plant parasitism.
-
-
-
Ecology and Evolution of the Sudden Oak Death Pathogen Phytophthora ramorum
Vol. 57 (2019), pp. 301–321More LessThe sudden oak and sudden larch death pathogen Phytophthora ramorum emerged simultaneously in the United States on oak and in Europe on Rhododendron in the 1990s. This pathogen has had a devastating impact on larch plantations in the United Kingdom as well as mixed conifer and oak forests in the Western United States. Since the discovery of this pathogen, a large body of research has provided novel insights into the emergence, epidemiology, and genetics of this pandemic. Genetic and genomic resources developed for P. ramorum have been instrumental in improving our understanding of the epidemiology, evolution, and ecology of this disease. The recent reemergence of EU1 in the United States and EU2 in Europe and the discovery of P. ramorum in Asia provide renewed impetus for research on the sudden oak death pathogen.
-
-
-
Resolving Fusarium: Current Status of the Genus
Vol. 57 (2019), pp. 323–339More LessThe fungal genus Fusarium is one of the most important groups of plant-pathogenic fungi and affects a huge diversity of crops in all climatic zones across the globe. In addition, it is also a human pathogen and produces several extremely important mycotoxins in food products that have deleterious effects on livestock and humans. These fungi have been plagued over the past century by different perspectives of what constitutes the genus Fusarium and how many species occur within the genus. Currently, there are conflicting views on the generic boundaries and what defines a species that impact disease diagnosis, management, and biosecurity legislation. An approach to defining and identifying Fusarium that places the needs of the community of users (especially, in this case, phytopathologists) to the forefront is presented in this review.
-
-
-
The Evolution, Ecology, and Mechanisms of Infection by Gram-Positive, Plant-Associated Bacteria
Vol. 57 (2019), pp. 341–365More LessGram-positive bacteria are prominent members of plant-associated microbial communities. Although many are hypothesized to be beneficial, some are causative agents of economically important diseases of crop plants. Because the features of Gram-positive bacteria are fundamentally different relative to those of Gram-negative bacteria, the evolution and ecology as well as the mechanisms used to colonize and infect plants also differ. Here, we discuss recent advances in our understanding of Gram-positive, plant-associated bacteria and provide a framework for future research directions on these important plant symbionts.
-
-
-
Activity and Phylogenetics of the Broadly Occurring Family of Microbial Nep1-Like Proteins
Vol. 57 (2019), pp. 367–386More LessNecrosis- and ethylene-inducing peptide 1 (Nep1)-like proteins (NLP) have an extremely broad taxonomic distribution; they occur in bacteria, fungi, and oomycetes. NLPs come in two forms, those that are cytotoxic to eudicot plants and those that are noncytotoxic. Cytotoxic NLPs bind to glycosyl inositol phosphoryl ceramide (GIPC) sphingolipids that are abundant in the outer leaflet of plant plasma membranes. Binding allows the NLP to become cytolytic in eudicots but not monocots. The function of noncytotoxic NLPs remains enigmatic, but the expansion of NLP genes in oomycete genomes suggests they are important. Several plant species have evolved the capacity to recognize NLPs as molecular patterns and trigger plant immunity, e.g., Arabidopsis thaliana detects nlp peptides via the receptor-like protein RLP23. In this review, we provide a historical perspective from discovery to understanding of molecular mechanisms and describe the latest developments in the NLP field to shed light on these fascinating microbial proteins.
-
-
-
Never Walk Alone: Clathrin-Coated Vesicle (CCV) Components in Plant Immunity
Vol. 57 (2019), pp. 387–409More LessAt the host–pathogen interface, the protein composition of the plasma membrane (PM) has important implications for how a plant cell perceives and responds to invading microbial pathogens. A plant's ability to modulate its PM composition is critical for regulating the strength, duration, and integration of immune responses. One mechanism by which plant cells reprogram their cell surface is vesicular trafficking, including secretion and endocytosis. These trafficking processes add or remove cargo proteins (such as pattern-recognition receptors, transporters, and other proteins with immune functions) to or from the PM via small, membrane-bound vesicles. Clathrin-coated vesicles (CCVs) that form at the PM and trans-Golgi network/early endosomes have emerged as the prominent vesicle type in the regulation of plant immune responses. In this review, we discuss the roles of the CCV core, adaptors, and accessory components in plant defense signaling and immunity against various microbial pathogens.
-
-
-
Molecular Interactions Between Smut Fungi and Their Host Plants
Vol. 57 (2019), pp. 411–430More LessSmut fungi are a large group of biotrophic plant pathogens that infect mostly monocot species, including economically relevant cereal crops. For years, Ustilago maydis has stood out as the model system to study the genetics and cell biology of smut fungi as well as the pathogenic development of biotrophic plant pathogens. The identification and functional characterization of secreted effectors and their role in virulence have particularly been driven forward using the U. maydis–maize pathosystem. Today, advancing tools for additional smut fungi such as Ustilago hordei and Sporisorium reilianum, as well as an increasing number of available genome sequences, provide excellent opportunities to investigate in parallel the effector function and evolution associated with different lifestyles and host specificities. In addition, genome analyses revealed similarities in the genomic signature between pathogenic smuts and epiphytic Pseudozyma species. This review elaborates on how knowledge about fungal lifestyles, genome biology, and functional effector biology has helped in understanding the biology of this important group of fungal pathogens. We highlight the contribution of the U. maydis model system but also discuss the differences from other smut fungi, which raises the importance of comparative genomic and genetic analyses in future research.
-
-
-
Understanding Adaptation, Coevolution, Host Specialization, and Mating System in Castrating Anther-Smut Fungi by Combining Population and Comparative Genomics
Vol. 57 (2019), pp. 431–457More LessAnther-smut fungi provide a powerful system to study host–pathogen specialization and coevolution, with hundreds of Microbotryum species specialized on diverse Caryophyllaceae plants, castrating their hosts through manipulation of the hosts’ reproductive organs to facilitate disease transmission. Microbotryum fungi have exceptional genomic characteristics, including dimorphic mating-type chromosomes, that make this genus anexcellent model for studying the evolution of mating systems and their influence on population genetics structure and adaptive potential. Important insights into adaptation, coevolution, host specialization, and mating system evolution have been gained using anther-smut fungi, with new insights made possible by the recent advent of genomic approaches. We illustrate with Microbotryum case studies how using a combination of comparative genomics, population genomics, and transcriptomics approaches enables the integration of different evolutionary perspectives across different timescales. We also highlight current challenges and suggest future studies that will contribute to advancing our understanding of the mechanisms underlying adaptive processes in populations of fungal pathogens.
-
Previous Volumes
-
Volume 62 (2024)
-
Volume 61 (2023)
-
Volume 60 (2022)
-
Volume 59 (2021)
-
Volume 58 (2020)
-
Volume 57 (2019)
-
Volume 56 (2018)
-
Volume 55 (2017)
-
Volume 54 (2016)
-
Volume 53 (2015)
-
Volume 52 (2014)
-
Volume 51 (2013)
-
Volume 50 (2012)
-
Volume 49 (2011)
-
Volume 48 (2010)
-
Volume 47 (2009)
-
Volume 46 (2008)
-
Volume 45 (2007)
-
Volume 44 (2006)
-
Volume 43 (2005)
-
Volume 42 (2004)
-
Volume 41 (2003)
-
Volume 40 (2002)
-
Volume 39 (2001)
-
Volume 38 (2000)
-
Volume 37 (1999)
-
Volume 36 (1998)
-
Volume 35 (1997)
-
Volume 34 (1996)
-
Volume 33 (1995)
-
Volume 32 (1994)
-
Volume 31 (1993)
-
Volume 30 (1992)
-
Volume 29 (1991)
-
Volume 28 (1990)
-
Volume 27 (1989)
-
Volume 26 (1988)
-
Volume 25 (1987)
-
Volume 24 (1986)
-
Volume 23 (1985)
-
Volume 22 (1984)
-
Volume 21 (1983)
-
Volume 20 (1982)
-
Volume 19 (1981)
-
Volume 18 (1980)
-
Volume 17 (1979)
-
Volume 16 (1978)
-
Volume 15 (1977)
-
Volume 14 (1976)
-
Volume 13 (1975)
-
Volume 12 (1974)
-
Volume 11 (1973)
-
Volume 10 (1972)
-
Volume 9 (1971)
-
Volume 8 (1970)
-
Volume 7 (1969)
-
Volume 6 (1968)
-
Volume 5 (1967)
-
Volume 4 (1966)
-
Volume 3 (1965)
-
Volume 2 (1964)
-
Volume 1 (1963)
-
Volume 0 (1932)