scholarly journals Importance of Molecular Data to Identify Fungal Plant Pathogens and Guidelines for Pathogenicity Testing Based on Koch’s Postulates

Pathogens ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1096
Author(s):  
Chitrabhanu S. Bhunjun ◽  
Alan J. L. Phillips ◽  
Ruvishika S. Jayawardena ◽  
Itthayakorn Promputtha ◽  
Kevin D. Hyde
Keyword(s):  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Molecular Data ◽  
Plant Diseases ◽  
Koch’S Postulates ◽  
Disease Symptoms ◽  
Fungal Plant Pathogens ◽  
Bradford Hill ◽  
Pathogenicity Testing ◽  
Koch's Postulates

Fungi are an essential component of any ecosystem, but they can also cause mild and severe plant diseases. Plant diseases are caused by a wide array of fungal groups that affect a diverse range of hosts with different tissue specificities. Fungi were previously named based only on morphology and, in many cases, host association, which has led to superfluous species names and synonyms. Morphology-based identification represents an important method for genus level identification and molecular data are important to accurately identify species. Accurate identification of fungal pathogens is vital as the scientific name links the knowledge concerning a species including the biology, host range, distribution, and potential risk of the pathogen, which are vital for effective control measures. Thus, in the modern era, a polyphasic approach is recommended when identifying fungal pathogens. It is also important to determine if the organism is capable of causing host damage, which usually relies on the application of Koch’s postulates for fungal plant pathogens. The importance and the challenges of applying Koch’s postulates are discussed. Bradford Hill criteria, which are generally used in establishing the cause of human disease, are briefly introduced. We provide guidelines for pathogenicity testing based on the implementation of modified Koch’s postulates incorporating biological gradient, consistency, and plausibility criteria from Bradford Hill. We provide a set of protocols for fungal pathogenicity testing along with a severity score guide, which takes into consideration the depth of lesions. The application of a standard protocol for fungal pathogenicity testing and disease assessment in plants will enable inter-studies comparison, thus improving accuracy. When introducing novel plant pathogenic fungal species without proving the taxon is the causal agent using Koch’s postulates, we advise the use of the term associated with the “disease symptoms” of “the host plant”. Where possible, details of disease symptoms should be clearly articulated.

scholarly journals Diagnosis of Fungal Plant Pathogens Using Conventional and Molecular Approaches

2021 ◽  
Author(s):  
Monika C. Dayarathne ◽  
Amin U. Mridha ◽  
Yong Wang
Keyword(s):  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Economic Loss ◽  
Rapid Identification ◽  
Plant Diseases ◽  
Morphological Observation ◽  
Pathogen Identification ◽  
Molecular Approaches ◽  
Fungal Plant Pathogens ◽  
One Fungus One Name

Fungi are a large group of eukaryotes found as saprophytes, pathogens or endophytes, which distribute in every corner of our planet. As the main pathogens, fungi can cause 70–80% of total plant diseases, leading to huge crop yield reduction and economic loss. For identification of fungal plant pathogens, mycologists and plant pathologists have mainly gone through two stages, viz. morphological observation and morphology/phylogeny, and the next era might be utilizing DNA barcodes as the tool for rapid identification. This chapter accounts i) the brief history of development for fungal identification tools and main concepts, ii) the importance and confusion of “One fungus, one name” for pathogen identification, iii) more or fewer species that we need in agricultural practice, and iv) the foreground of fungal plant pathogen identification. These will help to solve the practical problems of identification of fungal pathogens in agricultural production.

Survey Reveals a Broad Range of Fungal Pathogens and an Oomycete on Peonies in the United States

2019 ◽  
Vol 20 (4) ◽  
pp. 250-254
Author(s):  
Andrea R. Garfinkel ◽  
Gary A. Chastagner
Keyword(s):  
United States ◽  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Large Subunit ◽  
Ornamental Plants ◽  
The United States ◽  
Cut Flowers ◽  
Koch’S Postulates ◽  
Colletotrichum Spp ◽  
Koch's Postulates

Peonies, Paeonia lactiflora and hybrids, are popular ornamental plants grown in landscapes and as cut flowers. As with many ornamental plants, the information on the etiology of peony diseases is incomplete with varying amounts of detailed descriptive material; sometimes validation of Koch’s postulates is also lacking. In a survey to identify the range of diseases of peony in the United States, samples were obtained from 12 states. Fungal and oomycete plant pathogens recovered from symptomatic, diseased tissue were identified by morphology and BLAST identification of the internal transcribed spacer, glyceraldehyde 3-phosphate dehydrogenase, the 28s large subunit, and/or cytochrome c oxidase subunit 1 gene nucleotide sequences for representative isolates. Ten fungal or oomycete genera were identified, and Koch’s postulates were confirmed for selected plant pathogens found during this survey. New disease reports are generated for several states, including five genera never previously reported on peonies in the United States: a Botryosphaeria sp., multiple Colletotrichum spp., Mycocentrospora acerina, a Phoma sp., and Pilidium concavum. The information gained from this survey will provide plant disease diagnosticians and growers a more comprehensive resource for understanding the regional prevalence of peony diseases and subsequently making better disease management decisions.

scholarly journals Identification of Diverse Mycoviruses through Metatranscriptomics Characterization of the Viromes of Five Major Fungal Plant Pathogens

2016 ◽  
Vol 90 (15) ◽  
pp. 6846-6863 ◽  
Author(s):  
Shin-Yi Lee Marzano ◽  
Berlin D. Nelson ◽  
Olutoyosi Ajayi-Oyetunde ◽  
Carl A. Bradley ◽  
Teresa J. Hughes ◽  
...  
Keyword(s):  
High Throughput ◽  
Fungal Pathogens ◽  
Plant Pathogens ◽  
High Throughput Sequencing ◽  
Pathogenic Fungi ◽  
Plant Diseases ◽  
Plant Pathogenic Fungi ◽  
Content Type ◽  
Fungal Plant Pathogens ◽  
Viral Sequences

ABSTRACTMycoviruses can have a marked effect on natural fungal communities and influence plant health and productivity. However, a comprehensive picture of mycoviral diversity is still lacking. To characterize the viromes of five widely dispersed plant-pathogenic fungi,Colletotrichum truncatum,Macrophomina phaseolina,Diaporthe longicolla,Rhizoctonia solani, andSclerotinia sclerotiorum, a high-throughput sequencing-based metatranscriptomic approach was used to detect viral sequences. Total RNA and double-stranded RNA (dsRNA) from mycelia and RNA from samples enriched for virus particles were sequenced. Sequence data were assembledde novo, and contigs with predicted amino acid sequence similarities to viruses in the nonredundant protein database were selected. The analysis identified 72 partial or complete genome segments representing 66 previously undescribed mycoviruses. Using primers specific for each viral contig, at least one fungal isolate was identified that contained each virus. The novel mycoviruses showed affinity with 15 distinct lineages:Barnaviridae,Benyviridae,Chrysoviridae,Endornaviridae,Fusariviridae,Hypoviridae,Mononegavirales,Narnaviridae,Ophioviridae,Ourmiavirus,Partitiviridae,Tombusviridae,Totiviridae,Tymoviridae, andVirgaviridae. More than half of the viral sequences were predicted to be members of theMitovirusgenus in the familyNarnaviridae, which replicate within mitochondria. Five viral sequences showed strong affinity with three families (Benyviridae,Ophioviridae, andVirgaviridae) that previously contained no mycovirus species. The genomic information provides insight into the diversity and taxonomy of mycoviruses and coevolution of mycoviruses and their fungal hosts.IMPORTANCEPlant-pathogenic fungi reduce crop yields, which affects food security worldwide. Plant host resistance is considered a sustainable disease management option but may often be incomplete or lacking for some crops to certain fungal pathogens or strains. In addition, the rising issues of fungicide resistance demand alternative strategies to reduce the negative impacts of fungal pathogens. Those fungus-infecting viruses (mycoviruses) that attenuate fungal virulence may be welcome additions for mitigation of plant diseases. By high-throughput sequencing of the RNAs from 275 isolates of five fungal plant pathogens, 66 previously undescribed mycoviruses were identified. In addition to identifying new potential biological control agents, these results expand the grand view of the diversity of mycoviruses and provide possible insights into the importance of intracellular and extracellular transmission in fungus-virus coevolution.

scholarly journals The emergence of cereal fungal diseases and the incidence of leaf spot diseases in Finland

2008 ◽  
Vol 20 (1) ◽  
pp. 62 ◽  
Author(s):  
M. JALLI ◽  
P. LAITINEN ◽  
S. LATVALA
Keyword(s):  
Spring Wheat ◽  
Leaf Spot ◽  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Field Survey ◽  
Fungal Diseases ◽  
Cochliobolus Sativus ◽  
Pyrenophora Tritici Repentis ◽  
Fungal Plant Pathogens ◽  
First Time

Fungal plant pathogens causing cereal diseases in Finland have been studied by a literature survey, and a field survey of cereal leaf spot diseases conducted in 2009. Fifty-seven cereal fungal diseases have been identified in Finland. The first available references on different cereal fungal pathogens were published in 1868 and the most recent reports are on the emergence of Ramularia collo-cygni and Fusarium langsethiae in 2001. The incidence of cereal leaf spot diseases has increased during the last 40 years. Based on the field survey done in 2009 in Finland, Pyrenophora teres was present in 86%, Cochliobolus sativus in 90% and Rhynchosporium secalis in 52% of the investigated barley fields. Mycosphaerella graminicola was identified for the first time in Finnish spring wheat fields, being present in 6% of the studied fields. Stagonospora nodorum was present in 98% and Pyrenophora tritici-repentis in 94% of spring wheat fields. Oat fields had the fewest fungal diseases. Pyrenophora chaetomioides was present in 63% and Cochliobolus sativus in 25% of the oat fields studied.;

scholarly journals Biochar and Trichoderma spp. in management of plant diseases caused by soilborne fungal pathogens: a review and perspective

2021 ◽  
Vol 10 (15) ◽  
pp. e296101522465
Author(s):  
Erika Valente de Medeiros ◽  
Lucas Figueira da Silva ◽  
Jenifer Sthephanie Araújo da Silva ◽  
Diogo Paes da Costa ◽  
Carlos Alberto Fragoso de Souza ◽  
...  
Keyword(s):  
Soil Properties ◽  
Fungal Pathogens ◽  
Plant Disease ◽  
Plant Pathogens ◽  
Plant Diseases ◽  
Management Tool ◽  
Production Plant ◽  
Trichoderma Spp ◽  
Health Concept ◽  
Plant Disease Management

A better understanding of the use of biochar with Trichoderma spp. (TRI), considered the most studied tool for biological control, would increase our ability to set priorities. However, no studies exist using the two inputs on plant disease management. Here, we hypothesized that biochar and TRI would be used for the management of soilborne plant pathogens, mainly due to changes in soil properties and its interactions. To test this hypothesis, this review assesses papers that used biochar and TRI against plant diseases and we summarize the handling mechanisms for each input. Biochar acts by mechanisms: induction to plant resistance, sorption of allelopathic and fungitoxic compounds, increase of beneficial microorganisms, changes the soil properties that promote health and nutrient availability. Trichoderma as biocontrol agents by different mechanisms: mycoparasitism, enzyme and secondary metabolic production, plant promoter agent, natural decomposition agent, and biological agent of bioremediation. Overall, our findings expand our knowledge about the reuse of wastes transformed in biochar combined with Trichoderma has potential perspective to formulate products as alternative management tool of plant disease caused by soilborne fungal pathogen and add important information that can be suitable for development of strategy for use in the global health concept.

Localization and Visualization of Specific Gene Products in Fungal Plant Pathogens

2000 ◽  
Vol 6 (S2) ◽  
pp. 680-681 ◽  
Author(s):  
T. M. Bourett ◽  
K. J. Czymmek ◽  
T. M. Dezwaan ◽  
J. A. Sweigard ◽  
R. J. Howard
Keyword(s):  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Protein Localization ◽  
Infected Plant ◽  
Cell Interaction ◽  
Specific Gene ◽  
Gene Products ◽  
Tem Analysis ◽  
Fungal Plant Pathogens ◽  
Plant Pathogenesis

Specific gene products of both pathogens and hosts have been implicated as decisive elements during plant pathogenesis. While expression of some of these genes is constitutive, that of others is likely ephemeral and activated only during a particular stage of the interaction. Because the relative timing of expression may be critical, transcription and translation have often been addressed by extracting mRNA and proteins from infected plant tissue. This approach, however, cannot readily detect proteins of low abundance in bulk samples nor offer much useful information on cell-cell interaction. Only a cytological analysis that employs microscopy can resolve the temporal and spatial details of gene expression. Typically, such protein localization studies have required specific antibodies, but these large probe molecules do not diffuse into living or conventionally fixed cells of either fungal pathogens or plant hosts. For TEM analysis, these permeability-imposed limitations have been reduced by thin sectioning to render accessible antibody binding sites.

scholarly journals Nonhost Resistance in Arabidopsis-Colletotrichum Interactions Acts at the Cell Periphery and Requires Actin Filament Function

2006 ◽  
Vol 19 (3) ◽  
pp. 270-279 ◽  
Author(s):  
Chiyumi Shimada ◽  
Volker Lipka ◽  
Richard O'Connell ◽  
Tetsuro Okuno ◽  
Paul Schulze-Lefert ◽  
...  
Keyword(s):  
Actin Filament ◽  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Fluorescent Protein ◽  
Molecular Genetic ◽  
Molecular Genetic Analysis ◽  
Nonhost Resistance ◽  
Cell Periphery ◽  
Colletotrichum Species ◽  
Fungal Plant Pathogens

Pathogenesis of nonadapted fungal pathogens is often terminated coincident with their attempted penetration into epidermal cells of nonhost plants. The genus Colletotrichum represents an economically important group of fungal plant pathogens that are amenable to molecular genetic analysis. Here, we investigated interactions between Arabidopsis and Colletotrichum to gain insights in plant and pathogen processes activating nonhost resistance responses. Three tested nonadapted Colletotrichum species differentiated melanized appressoria on Arabidopsis leaves but failed to form intracellular hyphae. Plant cells responded to Colletotrichum invasion attempts by the formation of PMR4/GSL5-dependent papillary callose. Appressorium differentiation and melanization were insufficient to trigger this localized plant cell response, but analysis of nonpathogenic C. lagenarium mutants implicates penetration-peg formation as the inductive cue. We show that Arabidopsis PEN1 syntaxin controls timely accumulation of papillary callose but is functionally dispensable for effective preinvasion (penetration) resistance in nonhost interactions. Consistent with this observation, green fluorescent protein-tagged PEN1 did not accumulate at sites of attempted penetration by either adapted or nonadapted Colletotrichum species, in contrast to the pronounced focal accumulations of PEN1 associated with entry of powdery mildews. We observed extensive reorganization of actin microfilaments leading to polar orientation of large actin bundles towards appressorial contact sites in interactions with the nonadapted Colletotrichum species. Pharmacological inhibition of actin filament function indicates a functional contribution of the actin cytoskeleton for both preinvasion resistance and papillary callose formation. Interestingly, the incidence of papilla formation at entry sites was greatly reduced in interactions with C. higginsianum isolates, indicating that this adapted pathogen may suppress preinvasion resistance at the cell periphery.

scholarly journals Colletotrichum species associated with anthracnose of Pyrus spp. in China

2019 ◽  
Vol 42 (1) ◽  
pp. 1-35 ◽  
Author(s):  
M. Fu ◽  
P.W. Crous ◽  
Q. Bai ◽  
P.F. Zhang ◽  
J. Xiang ◽  
...  
Keyword(s):  
Plant Pathogens ◽  
Novel Species ◽  
Phylogenetic Analyses ◽  
Koch’S Postulates ◽  
Colletotrichum Species ◽  
Organ Specific ◽  
Pathogenicity Tests ◽  
Koch's Postulates

Colletotrichum species are plant pathogens, saprobes, and endophytes on a range of economically important hosts. However, the species occurring on pear remain largely unresolved. To determine the morphology, phylogeny and biology of Colletotrichum species associated with Pyrus plants, a total of 295 samples were collected from cultivated pear species (including P. pyrifolia, P. bretschneideri, and P. communis) from seven major pear-cultivation provinces in China. The pear leaves and fruits affected by anthracnose were sampled and subjected to fungus isolation, resulting in a total of 488 Colletotrichum isolates. Phylogenetic analyses based on six loci (ACT, TUB2, CAL, CHS-1, GAPDH, and ITS) coupled with morphology of 90 representative isolates revealed that they belong to 10 known Colletotrichum species, including C. aenigma, C. citricola, C. conoides, C. fioriniae, C. fructicola, C. gloeosporioides, C. karstii, C. plurivorum, C. siamense, C. wuxiense, and two novel species, described here as C. jinshuiense and C. pyrifoliae. Of these, C. fructicola was the most dominant, occurring on P. pyrifolia and P. bretschneideri in all surveyed provinces except in Shandong, where C. siamense was dominant. In contrast, only C. siamense and C. fioriniae were isolated from P. communis, with the former being dominant. In order to prove Koch's postulates, pathogenicity tests on pear leaves and fruits revealed a broad diversity in pathogenicity and aggressiveness among the species and isolates, of which C. citricola, C. jinshuiense, C. pyrifoliae, and C. conoides appeared to be organ-specific on either leaves or fruits. This study also represents the first reports of C. citricola, C. conoides, C. karstii, C. plurivorum, C. siamense, and C. wuxiense causing anthracnose on pear.

scholarly journals Fungal Pathogens Affecting the Production and Quality of Medical Cannabis in Israel

Plants ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 882
Author(s):  
Shachar Jerushalmi ◽  
Marcel Maymon ◽  
Aviv Dombrovsky ◽  
Stanley Freeman
Keyword(s):  
Fungal Pathogens ◽  
Plant Pathogens ◽  
Pathogenic Fungi ◽  
Plant Diseases ◽  
Soilborne Pathogens ◽  
Medical Cannabis ◽  
Plant Parts ◽  
Commercial Cultivation

The use of and research on medical cannabis (MC) is becoming more common, yet there are still many challenges regarding plant diseases of this crop. For example, there is a lack of formal and professional knowledge regarding fungi that infect MC plants, and practical and effective methods for managing the casual agents of disease are limited. The purpose of this study was to identify foliar, stem, and soilborne pathogens affecting MC under commercial cultivation in Israel. The predominant major foliage pathogens were identified as Alternaria alternata and Botrytis cinerea, while the common stem and soilborne pathogens were identified as Fusarium oxysporum and F. solani. Other important fungi that were isolated from foliage were those producing various mycotoxins that can directly harm patients, such as Aspergillus spp. and Penicillium spp. The sampling and characterization of potential pathogenic fungi were conducted from infected MC plant parts that exhibited various disease symptoms. Koch postulates were conducted by inoculating healthy MC tissues and intact plants with fungi isolated from infected commercially cultivated symptomatic plants. In this study, we report on the major and most common plant pathogens of MC found in Israel, and determine the seasonal outbreak of each fungus.

scholarly journals Assessment of Fungal Pathogens Affecting the Weed Conyza bonariensis in Argentina

2018 ◽  
Vol 10 (3) ◽  
pp. 62
Author(s):  
Martin Bonacci ◽  
Ángela N. Formento ◽  
Fernando Daita ◽  
Melina Sartori ◽  
Miriam Etcheverry ◽  
...  
Keyword(s):  
Fungal Pathogens ◽  
Alternative Methods ◽  
Weed Species ◽  
Koch’S Postulates ◽  
Fungal Isolates ◽  
Conyza Bonariensis ◽  
Pesticide Reduction ◽  
Colletotrichum Spp ◽  
And Control ◽  
Koch's Postulates

In the last years Conyza bonariensis has become an important weed and control is difficult with the use of current technology in Argentinean pampas region. The increasing prevalence of herbicide-resistant weed species, public concern related to pesticide use and the introduction of government policies for pesticide reduction, is driving the search for alternative methods to chemical control. The aims of the present study were to detect fungal diseases associated with C. bonariensis, to identify fungal isolates from the symptomatic leaves and to confirm through Koch’s postulates the isolates pathogenicity. Mycological analysis of symptomatic leaves showed the presence of twelve genera of filamentous fungi. Among 116 isolates, Colletotrichum spp. was the most prevalent genus followed by Nigrospora spp. and Septoria spp. In the pathogenicity assays, 22 out of 116 isolates were able to comply with the Koch’s postulates. The pathogenic isolates were included into three genera Alternaria spp., Colletotrichum spp. and Septoria spp. This study provides the first report that demonstrates pathogenicity of fungal isolates on C. bonariensis in Argentina and represents the first step in a future biocontrol program.

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